Weird timing issue...
Jon R. Pickens
something very strange with the timing.
Basically, while looking down on the harmonic balancer, while using a
timing light, I see that I have it set at around 4 degrees BTDC at
idle. When I rev the engine, the timing mark moves in the direction
the engine is spinning...as if it's retarding rather than advancing! I
KNOW this is wrong, because I've time this engine before. I know that
the timing mark should move the opposite direction that the engine is
spinning (engine spinning clockwise, advancing the timing should move
it counter-clockwise).
This isn't exactly a complicated setup... 350ci Chevy with a HEI
distributor, vacuum advance. What the Hell could be causing this? The
vacuum advance module was replaced with a brand-new one.
What's even stranger is, the same thing happens regardless of whether I
use ported or manifold vacuum as the source to the advance module.
Shouldn't one produce exactly the opposite effect of the other?
FWIW, the only thing that's been changed was, I jumpered the 1st and
3rd pins of the 5-pin module together to bypass the ESC (cheapo
ECM-like device that retards spark based on input from a knock sensor).
This mod was/is GM approved and was released in a service bulletin
years ago.
Help.
~jp
aarcuda69062
<1148220788....@i39g2000cwa.googlegroups.com>,
Your distributor has both mechanical advance and vacuum advance.
(plus the now disabled electronic retard)
First, check what is happening with the vacuum advance
disconnected, (this is how you should be setting base timing
anyway) if it is still retarding, then one possibility is that
someone has monkeyed with the mechanical advance and put it
together backwards.
Take the distributor cap off (don't lose any parts this time)
give the rotor a twist, it should only move in the clockwise
direction.
Take the rotor off, check that the bob weights are able to move
freely against the springs (there -are- springs aren't there?).
Third possibility is that your timing chain is really, really
loose.
Jon R. Pickens
mechanical advance. The springs and weights are in place, and should
be as functional as they were prior to all this.
I set initial timing with the vacuum advance disconnected and a plug on
the vacuum port on the carb. I'll disconnect it again and watch the
timing change while I rev it.
The timing chain is the same age as the engine (2 years -/+) and was
not disturbed while the truck wasn't running.
I can't imagine that the ignition module would affect this.
~jp
aarcuda69062
<1148223568....@y43g2000cwc.googlegroups.com>,
"Jon R. Pickens" <jonr...@gmail.com> wrote:
> Ok... When I had the distributor out, I didn't mess with the
> mechanical advance. The springs and weights are in place, and should
> be as functional as they were prior to all this.
>
> I set initial timing with the vacuum advance disconnected and a plug on
> the vacuum port on the carb. I'll disconnect it again and watch the
> timing change while I rev it.
Post back with the results.
If you have a dwell meter, connect it to the coil negative, dwell
should equal one degree for each 100RPM of engine speed;
i.e.,
700 RPM = 7 degrees of dwell.
1500 RPM = 15 degrees of dwell.
2500 RPM = 25 degrees of dwell.
> The timing chain is the same age as the engine (2 years -/+) and was
> not disturbed while the truck wasn't running.
>
> I can't imagine that the ignition module would affect this.
Maybe if the magnet in the pole piece is cracked.
Jon R. Pickens
> > the vacuum port on the carb. I'll disconnect it again and watch the
> > timing change while I rev it.
>
> Post back with the results.
Same thing... no difference with the vacuum advance unplugged and the
port capped off. Timing was at around 4 degrees BTDC at that point.
It was running like crap, and when I revved it up, it backfired a HUGE
puff of smoke out of the carb. I plugged a vacuum gauge to the
manifold vacuum port, and played with the idle mixture screws to get
max vacuum. I advanced timing quite a bit to do the same, and was
pulling around 14" Hg. At this point the timing is set to about 10
degrees BTDC.
This'll make you wonder why I bothered posting back... I haven't
checked to see what the advance is doing now that I've reset timing at
idle. Probably the same though. Just thought I'd update you with the
previous results. I've been out there for hours, but I'm also trying
to correct last minute wiring issues. I have a few loose harnesses
that I'm trying to determine where they went. What's bad is, the
factory wiring manual is being little help. The closest thing I can
find to my engine in there is a V6 California engine. Hmm...Mine is a
V8 Tennessee truck. I'm positive it was sold new in TN, as it was a
Police truck prior to me buying it.
I have a nice new puddle of burnt tranny fluid in the parking lot
too...the property managers are gonna love that. It keeps dripping on
the exhaust while I'm fiddling with the engine, and that makes me
understandably paranoid :-)
~jp
Jon R. Pickens
better made it respond much better... but after I eat a bite and let
it cool down a bit, I will be out there checking the advance with the
timing light while I rev it.
~jp
SnoMan
wrote:
>Ok, so I'm trying to tune my engine to idle better, and I'm seeing
If engine runs okay, you may be making more out this than there is. It
could be a latencey problem with your timing light. (the delaty
between when it receives the pulse input and triggers that light)
which would cause exactly what you see.
-----------------
The SnoMan
www.thesnoman.com
Jon R. Pickens
degrees BTDC. It idles, ok, with a single miss here and there. It's
harder starting, so I should probably pull the timing back till it's
not.
When I rev it, it backfires. A huge puff of smoke shot through the top
of the air cleaner element. (I have one of those open, foam element
air cleaners)
As far as timing retarding....no, it's actually doing that. With or
without the vacuum advance connected.
Ideas on the timing?? I've never had an engine that backfired until
yesterday, so I don't know what causes it.
Valve timing has not changed...
~jp
wayne c
"Jon R. Pickens" <jonr...@gmail.com> wrote in message
news:1148258021.4...@i39g2000cwa.googlegroups.com...
Jon R. Pickens
Well... would that matter as long as timing could still be set and
adjusted? I didn't have a problem getting it to go down in there when
I reinstalled it. I'd marked the outer (adjustable) and inner
(rotating) portions of the pickup coil before I removed it. When I
slid it back in, both marks aligned properly--the first time I might
add, guess I got lucky.
What kinds of issues could the distro being off by a tooth cause? How
does it relate to certain issues?
Thanks,
~jp
Whitelightning
drive rotates as the distrib is pulled out, and when it goes back it will be
at least one tooth off..
I dont remember what year this rig your working on, but if its a carb, one
tooth off shouldn't matter, as it won't have a cam sensor or crank sensor,
cam sensor being part of the distrib on many models, as such a tooth or two
off wont hurt a thing, as long as you can rotate the distrib enough to get
it in time.
Does it back fire through the carb regardless of where timing is set? and if
so are you sure you dont have #5 and #7 reversed in the firing order(common
mistake)? are you sure you have the vacumm advance connected to the correct
vacumm source? Wrong one will cause vacumm advance to work too soon. source
has to ported, not manifold.
How long has this thing been down?
Whitelightning
Jon R. Pickens
> I dont remember what year this rig your working on, but if its a carb, one
'86 K5 Blazer, 350 (non-stock, originally had a 305), carbed (600cfm
Edelbrock, elec. choke, vac. 2ndaries)
> Does it back fire through the carb regardless of where timing is set?
Yep.
> are you sure you dont have #5 and #7 reversed in the firing order...
I'll double check it tomorrow. I followed the Haynes manual when
putting the plug wires on. I put them on in order of firing, starting
with piston #1.
I have seen a "corrected" HEI cap, that's wired internally as to let
you put the plug wires on in a sensible order--(clockwise from left
front) 2-4-6-8-7-5-3-1. I *so* wished I had one, lol...
> are you sure you have the vacumm advance connected to the correct
> vacumm source?
Yep...ported...
> How long has this thing been down?
Caught fire and burned up the harness on 12.28.2005. Started for the
first time 5.20.2006 (yesterday). So it's been a while.
~jp
HDS
"Jon R. Pickens" <jonr...@gmail.com> wrote in message news:1148220788....@i39g2000cwa.googlegroups.com...
> Ok, so I'm trying to tune my engine to idle better, and I'm seeing
> something very strange with the timing.
>
> Basically, while looking down on the harmonic balancer, while using a
> timing light, I see that I have it set at around 4 degrees BTDC at
> idle.
----------
Ok, I've read the other post; this is what I would do:
1. Double check that all you spark plug wires are routed correctly.
2.) Yank that thing out (Distrib), and set your motor to TDC, number one pistion.
3.) Insert the distrib, then pull it out again. Turn the rotor 180 degress, and put it back in.
Each time you do this, it'll move the rotor alittle bit farter each time. Repeat untill the
rotor is facing the number one spark plug connection in the cap. (you dont need to pull
the distrib ALL the way out, just enough to disengage the sprockets).
4.) Hook your cap and spark plug wire up, and start it up. Set the timing at TDC, not BTDC.
hook up your vac lines...enjoy
HDS
ShoeSalesman
a lean mix can cause a backfire.
set your base to about 10 before TDC.
you should see about 25 to 30 deg of advance with the vac and weights
when rev'ed up.
when you advance timing the idle speed will increase.
tom
with the vacum disconnect the TIMING degrees will change if u REV the
engine, due to the CENTRIPHCAL force on the Springs that the rotor
mounts onto ( OLDER distributors with POINTS.)
This is why u Set the timing on those engines at a CERTAIN RPM.
I donnot remember ( SENIOR MOMENT) what we called the advance that works
with those springs., this is why the rotor will move if you turn it
while the distributor is in place.
265/283/327/350/400 engines
--
It Doesnot Take Brains To
Get A High Paying Job!
All You Need Is A College Degree
David Johnson
"Jon R. Pickens" <jonr...@gmail.com> wrote in message
news:1148220788....@i39g2000cwa.googlegroups.com...
advance could be hooked up wrong. Take the cap off and use your mouth and
suck on the end of the vaccum line, it should pull the diaphram in moving
the arm in toward the vaccum pod. I don't think it is possible but maybe you
ended up with a advance from some odd ball reverse motor. Stuck weights just
wouldn't move, no change in timing but make sure they are free. Manifold or
ported doesn't make a diffrence on which way your vaccum advance works, its
vaccum no matter if its on all the time or not. Distributor position off
won't cause this problem, you can put your distributor in any direction just
make sure you are pointing at number one @ tdc. This isn't your problem, it
is running so you aren't 180 off. Installing small blocks in vehicles not
originally equipped with them you often have to turn distrubutors way off
for clearance then move your wires to appropriate position. Double check
your module wireing, just to make sure. Also double check your plug wires
for correct order. To backfire through carb you either have severe advance
allowing fire befoe intake valve closes, wrong fireing order or a bad intake
valve. let us know what happens.
Jon R. Pickens
> 1-8-4-3-6-5-7-2
That's how I wired it...
> a lean mix can cause a backfire.
> set your base to about 10 before TDC.
> you should see about 25 to 30 deg of advance with the vac and weights
> when rev'ed up.
> when you advance timing the idle speed will increase.
This lean mix business has me thinking...the only change to the carb
was the smaller jets. I'll find the old ones and reinstall them.
The retarding of the spark is occuring with or without the vacuum
advance connected.
Thanks,
~jp
Jon R. Pickens
> This doesn't even seem mechanically possible. There is no way a vaccum
> advance could be hooked up wrong.
Well the timing is retarding even with the vacuum advance disconnected.
This should STILL be impossible though... All I know is, the timing
gauge/tab above the harmonic balancer is marked something like "12 - 8
- 4 - 0 - 4 - 8" and says "before" on the left hand side and "after" on
the right. I set timing at idle to be about 8 degress on the "before"
side. When I rev it, the mark moves to the right. It's completely
asinine. And I KNOW that when I timed it in the past it went the
opposite way (advanced) when I revved it.
> I don't think it is possible but maybe you ended up with a advance
> from some odd ball reverse motor.
The problem is occuring even with the vacuum advance disconnected.
> Stuck weights just wouldn't move, no change in timing but make sure
> they are free.
I concour, and they are free to move, springs are functioning too.
> Manifold or ported doesn't make a diffrence on which way your vaccum
> advance works, its vaccum no matter if its on all the time or not.
Again, I agree... whether it's ported or manifold vacuum should only
change when the vacuum advance kicks in and whether it stays
"advanced". Although, connecting to the manifold vacuum source *could*
cause this (high vacuum at idle=max advance...crack open throttle,
manifold vacuum drops, timing retards) but that's not the case. Again,
it happens regardless of whether that vacuum advance is even connected
to a vacuum source. I did try the manifold vacuum as a test--no
difference.
> Distributor position off won't cause this problem, you can put your
> distributor in any direction just make sure you are pointing at number
> one @ tdc.
Agreed.
> This isn't your problem, it is running so you aren't 180 off.
Also agreed...
> Installing small blocks in vehicles not originally equipped with them you
> often have to turn distrubutors way off for clearance then move your wires
> to appropriate position.
It's a K5 Blazer...originally had a 305. This is a 350 that was a new
crate motor, installed 2 years ago.
> Double check your module wireing, just to make sure. Also double check
> your plug wires for correct order. To backfire through carb you either have
> severe advance allowing fire befoe intake valve closes, wrong fireing order
> or a bad intake valve. let us know what happens.
Here is what's different about the engine POST-fire...
1) The module wiring is a mod/hack that I pulled off these here
newsgroups as well as a few websites. It involves disconnecting the
rear harness coming out of the HEI although and then jumpering pins 1
and 3 on the pickup-coil side of the ignition module. The pickup is
connected to pins 2 and 3. Basically, either pin 1 or 3 is an "output"
and the other is an "input" in a manner of speaking. The old ESC
(elec. spark control/wannabe ECM) just retarded spark based on input
from a knock sensor. It got the signal to spark based on the
previously mentioned "output" of the ignition module and sent the
signal back to the module's "input". That's the simplified
explanation. Either way, by eliminating the ESC, and jumpering pins 1
and 3 together, you just create a loop that allows the engine to run.
It's a Chevy-approved mod/hack. I did this because I could not find a
replacement wiring harness to go back to the ESC. The original harness
was toasted in the fire. Plus I read that the ESC can cause problems
when it goes south, and it's a real performance killer.
2) 5 minutes before the fire, I'd changed the jets to smaller ones.
This could cause a lean condition off idle couldn't it?
When I get out of work today I'll get cracking...
Thanks,
~jp
SnoMan
wrote:
>Well... it doesn't run ok. I reset the timing at idle up to about 8-10
What year is this engine and ignition system and is it is a like year
truck? This is a interesting problem that I have never seen before but
I need more data to suggest a course of action.
-----------------
The SnoMan
www.thesnoman.com
SnoMan
of the distributor as the advance mechanism may be damaged.
On 21 May 2006 20:37:49 -0700, "Jon R. Pickens" <jonr...@gmail.com>
wrote:
-----------------
The SnoMan
www.thesnoman.com
Jon R. Pickens
emissions package. My factory wiring manual leads me to believe this.
It was a Police truck originally; maybe some gov't vehicles are ordered
to comply with the strictest emissions standards...?
Currently a 350ci. I ordered the 290hp crate engine from a dealer.
It's like the 260hp, but with a slightly hotter cam. I actually
would've ordered the 260hp version in retrospect.
The 260hp engine was only warrantied up to a 1985 truck. I could
either spend $300 on an extended warranty of sorts, or for the same
extra $300 get the 290hp.
The distributor was the stock unit from the 305. It's a HEI with the
5-pin module, modded to work like a 4-pin. Although it's a
factory-approved mod, I gotta wonder about it. Especially since the
whole purpose of the 5-pin setup is to retard timing based on knock.
Now technically, that should be disabled (because of the mod), and the
knock sensor and ESC are no longer connected. Still...has me wondering
if I shouldn't throw a 4-pin module in there.
I think the pickup coil should be fine. It's obviously doing its job,
and it's a fairly passive device. I couldn't imagine that it could
"slip" in any way. When I had the distributor out, I didn't disturb
it. I only pulled the distributor to clean it out. The fire melted a
hole in the cap and there was plenty of garbage in there. The only way
I could realistically do a good job of cleaning it out was to remove
it. I only used a non-conductive spray cleaner for electronics (motors
and alternators) that I got from a parts store.
Engine is grounded off the passenger-side head via a strap to the
firewall. Testing for continuity between any metal part of the engine
and the negative terminal on the battery shows a good connection.
The last thing I did before the fire was re-jet the carb for smaller
jets. It was running extremely rich at the time. I don't believe I
under-jetted it. I followed the suggestions of many people and
actually only went down like, one size...some folks suggested I try
much smaller jets.
I don't think it would've leaned it out THAT much...and with this
weird-ass timing thing, I'm leaning toward it.
~jp
aarcuda69062
<1148258021.4...@i39g2000cwa.googlegroups.com>,
"Jon R. Pickens" <jonr...@gmail.com> wrote:
Back fire is caused by;
Late ignition timing
Lean fuel mixture
Leaking intake valve
Worn exhaust lobe on the cam
Crossed ignition wires (crossfire or plugged in wrong)
The fact that you're seeing the timing retard with your timing
light makes -that- the prime suspect.
Sorry Jon, I'm not buying the "everything was fine before the
fire" bit. It's been 5 months, so, a lot can be forgotten, and
-something- had to be the source of the flame that started the
fire when you had a fuel leak.
Take the cap and rotor off, look closely at the mechanical
advance mechanism.
In 36 years as a mechanic, and [too] many of them as a
driveability tech in a Chevy dealership, I've seen this problem
more than once, and often times it traced back to something wrong
in the mechanical advance. Ozone inside the cap from the arc
causes rust, rust causes binding, from here it's either it's
doing it because it is bound up or it's doing it because someone
was in there before.
IIRC, you've had a vacuum gauge on this thing since you got it
running, if the vacuum was steady, I'd rule out valvetrain
problems for the time being.
Jon R. Pickens
aarcuda69062 wrote:
> Back fire is caused by;
> Late ignition timing
> Lean fuel mixture
> Leaking intake valve
> Worn exhaust lobe on the cam
> Crossed ignition wires (crossfire or plugged in wrong)
Well, since the timing is retarding rather than advancing, (ie: later
timing) that could be a problem. I did attempt to lean it out. No
word on the valves or cam, but the long block is 2 years old.
It's possible that I miswired the distributor. I wasn't replacing one
at a time, the wires were burned up.
> The fact that you're seeing the timing retard with your timing
> light makes -that- the prime suspect.
Agreed.
> Sorry Jon, I'm not buying the "everything was fine before the
> fire" bit. It's been 5 months, so, a lot can be forgotten, and
> -something- had to be the source of the flame that started the
> fire when you had a fuel leak.
LOL... *I* was the cause of the fire. As I said, I was trying to get
it to lean out. It ran terribly rich after the new engine went in.
Basically, the dude that put it in said the Quadrajet was in need of a
rebuild. I needed a carb immediately, so I drove it as it for like a
week, then bought an Edelbrock Performer 600cfm carb. That's when it
started running rich.
When I was leaning it out (changing to smaller jets) in December, I had
just driven home from work. The engine was still hot. I reconnected
everything except the fuel line (Doh!) and when I tried to start it,
the fuel pump caused a bunch of gas to shoot onto the hot engine via
the loose fuel line that was laying on top of the intake.
When I tried to start it, it (obviously) didn't start. I heard a
whooshing, boom kinda sound, and saw flames shoot out all 4 sides of
the loosely closed hood.
No prior problems caused the fire. It was just me making a stupid
mistake.
> Take the cap and rotor off, look closely at the mechanical
> advance mechanism.
> In 36 years as a mechanic, and [too] many of them as a
> driveability tech in a Chevy dealership, I've seen this problem
> more than once, and often times it traced back to something wrong
> in the mechanical advance. Ozone inside the cap from the arc
> causes rust, rust causes binding, from here it's either it's
> doing it because it is bound up or it's doing it because someone
> was in there before.
The mechanical advance opens smoothly. I checked the movement of the
weights before I reassembled it. If that were the case, it should
simply not advance right? It should retard timing should it?
> IIRC, you've had a vacuum gauge on this thing since you got it
> running, if the vacuum was steady, I'd rule out valvetrain
> problems for the time being.
Yeah, manifold vacuum is pretty steady at idle. It dumps to zero when
I rev it.
~jp
aarcuda69062
<1148307549.1...@j33g2000cwa.googlegroups.com>,
"Jon R. Pickens" <jonr...@gmail.com> wrote:
> The mechanical advance opens smoothly. I checked the movement of the
> weights before I reassembled it. If that were the case, it should
> simply not advance right? It should retard timing should it?
When you twist the plate that the rotor screws down to, which
direction makes the advance weights open up? Clock wise or
counter-clockwise.
Stated another way, pulling the advance weights out (as
centrifugal force would do) should make the rotor (or rotor
plate) move clockwise.
If the advance mechanism is put together wrong, it will still
open, but the timing will retard instead of advance.
Jon R. Pickens
> direction makes the advance weights open up? Clock wise or
> counter-clockwise.
> Stated another way, pulling the advance weights out (as
> centrifugal force would do) should make the rotor (or rotor
> plate) move clockwise.
> If the advance mechanism is put together wrong, it will still
> open, but the timing will retard instead of advance.
I'll check... But it did work fine before the fire... When I had the
distributor out, I did NOT removed, adjust, or otherwise screw around
with the mechanical advance--AT ALL.
When I said "I checked the movement of the weights before I reassembled
it" I meant, reassembled the distributor, not the mechanical advance.
By reassembling the distributor, I mean, installed a new condensor,
module, rotor, cap, button and coil, and plug wires.
But I will check it again.
~jp
Jon R. Pickens
It's possible that I screwed that up. Is one side of the coil
grounded? Seems like it would have to be in order for anything to
happen.
~jp
SnoMan
wrote:
> Still...has me wondering
>if I shouldn't throw a 4-pin module in there.
At this stage of it, I would try it.
-----------------
The SnoMan
www.thesnoman.com
Jon R. Pickens
I'm thinking it shouldn't, however if one side of the pickup is
grounded (as it probably has to be for it to work) then it's possible
that the wrong side of the module is being grounded.
~jp
Jon R. Pickens
It states in the 3rd message:
"The polarity of the signal going into the HEI module is VERY
important."
then...
"On an engine, a symptom of reversed pickup wires is ignition timing
which is about 20 to 50 degrees retarded, and the timing bounces around
a lot. When it is connected correctly, the timing is very consistent,
and is close to where you set the static timing."
~jp
Jon R. Pickens
interesting)
"One thing to watch with all these modules is to correctly phase the
variable reluctor pickup. The waveform looks like this:"
/\
/ \
/ \
----/ \x /------
\ /
\ /
\ /
V
"The ignition should trigger at the zero crossing, point "x". that is
the most stable point vs RPM. If the polarity of the trigger is
reversed, the ignition will likely trigger on the rising edge, ***THE
POSITION OF WHICH CHANGES WITH RPM***."
~jp
SnoMan
wrote:
>and... (yes I realize I'm flooding the thread but still, this is
THe rising wave well not change from its trigger point regarless of
RPM BUT, the fall wave relative to crank postion can because the decay
rate of coil in pickup is constant over a fixed time interval so as
RPM increase it will cross zero axis at a further and further point as
RPM increases (relative to crank postion) and in effect, retarding the
timing signal. Incorrect polarity and/or wirng could cause your
problem. The key to your problem is in the pickup and its inteface
with ECM.
Jon R. Pickens
> THe rising wave well not change from its trigger point regarless of
> RPM BUT, the fall wave relative to crank postion can because the decay
> rate of coil in pickup is constant over a fixed time interval so as
> RPM increase it will cross zero axis at a further and further point as
> RPM increases (relative to crank postion) and in effect, retarding the
> timing signal. Incorrect polarity and/or wirng could cause your
> problem. The key to your problem is in the pickup and its inteface
> with ECM.
Well rock on... Here at work, I get my best thinking done out on the
loading dock (smoking area). I was leaning against the wall and it hit
me.
This makes a LOT of sense. That is the ONLY way I could imagine spark
actually retarding with RPM increases.
~jp
SnoMan
wrote:
>SnoMan wrote:
I have put some thought into this and I agree it does add up and could
explain your problem fully. There is always a cause for a problem and
you need to understand it to find a solution. Your comments of the
trigger signal made it cyrstalize for me as to what was going on here.
It all adds up.
-----------------
The SnoMan
www.thesnoman.com
Jon R. Pickens
I know a *little*) The wave WAS running in reverse. I just walked
back in the apartment not 2 minutes.
THE TIMING ISSUE HAS BEEN LAID TO REST!
Currently set to about 13 degrees BTDC @ idle with the vacuum advance
disconnected, pulling about 14-15" Hg off the manifold. The mechanical
advance is doing its job, advancing with engine speed... No more
backfiring too. I'll take it!
Many thanks for your help, Sir...as well to anyone else who replied
with suggestions.
~jp
Jon R. Pickens
~jp
SnoMan
wrote:
>Yep... basic AC voltage theory...(I'm by no means an electrician, but
You are quite welcome. I am here to help not to get brownie points.
Your problem was curious as I never had seen one like that so I wanted
to find the cause. Do not dish yourself on electrical knowledge
because you knew more than most and enough to understand what was
happening when I connected the dots for you.
-----------------
The SnoMan
www.thesnoman.com
Jon R. Pickens
hints.
I can't count how many good ideas I come up with on the loading dock at
work, lol... more than I do at my desk, that's for sure.
Once I got a few 'keywords' down, I was able to pull up quite a bit on
the subject via Google. I find it interesting that I've never heard
anything about this before.
And apparently the 5-pin ignition module is uncommon enough that I'm
very unlikely to find much on it. I may actually post some of this
info on my site for future linking/reference.
Surely someone else will need this info someday.
~jp
David Johnson
"Jon R. Pickens" <jonr...@gmail.com> wrote in message
news:1148349674.8...@j33g2000cwa.googlegroups.com...
>up with this anwer unless it was just luck. glad ya got it going, now I can
>watch a tv show without this problem floating through my brain every 10
>min.
aarcuda69062
<1148336468.9...@g10g2000cwb.googlegroups.com>,
"Jon R. Pickens" <jonr...@gmail.com> wrote:
Glad you got it figured out Jon.
I'm a bit puzzled though...
Been a few years since I was inside an old HEI but two things
come to mind;
1) aren't the terminals on the pole piece different sizes to keep
reversing them from happening?
2) aren't the module terminals where the pole piece plugs in
labeled 'G' for the green wire and 'W' for the white wire?
ShoeSalesman
The Jones'
>
> 1) The module wiring is a mod/hack that I pulled off these here
> newsgroups as well as a few websites. It involves disconnecting the
> rear harness coming out of the HEI although and then jumpering pins 1
> and 3 on the pickup-coil side of the ignition module. The pickup is
> connected to pins 2 and 3. Basically, either pin 1 or 3 is an "output"
> and the other is an "input" in a manner of speaking. The old ESC
> (elec. spark control/wannabe ECM) just retarded spark based on input
> from a knock sensor. It got the signal to spark based on the
> previously mentioned "output" of the ignition module and sent the
> signal back to the module's "input". That's the simplified
> explanation. Either way, by eliminating the ESC, and jumpering pins 1
> and 3 together, you just create a loop that allows the engine to run.
>
> It's a Chevy-approved mod/hack. I did this because I could not find a
> replacement wiring harness to go back to the ESC. The original harness
> was toasted in the fire. Plus I read that the ESC can cause problems
> when it goes south, and it's a real performance killer.
>
> 2) 5 minutes before the fire, I'd changed the jets to smaller ones.
> This could cause a lean condition off idle couldn't it?
>
> When I get out of work today I'll get cracking...
>
> Thanks,
>
> ~jp
>
Just my 2 cents worth but...............
I recall the jumping of wires to eliminate the esc module, I cant remember
the specifics of it but if it is what you say it is , just an input and and
output then the pick up is waiting on an input from the knock sensor thru
the module? basically an electrical/electronic signal? what if all you did
by jumping the wires is send a signal to the pick up to retard the timing
due to the signals coming into the input connector?
I am going to look for the bulletin and info on this mod.
redeye-racing
anyone mentioned this and i don't know if it's relevant...i came across
a similar situation a few times on 88-94 chevys...HUNTING
timing..timing moves all over...some times runs ok till your on the
gas, some times idles bad...the rector wheel with the magnets on it,on
the distributor shaft was loose, and spinning on the shaft...sometimes
they can move at idle and sometimes they need instantaneous
acceleration, like you revving it up, to move. unfortunately there is
no fix for this, you have to replace the distributor assembly...i've
seen this about 1/2 a dozen times...its not that commen
let me know what happens.
redeye.racing
Jon R. Pickens
> come to mind;
> 1) aren't the terminals on the pole piece different sizes to keep
> reversing them from happening?
> 2) aren't the module terminals where the pole piece plugs in
> labeled 'G' for the green wire and 'W' for the white wire?
Well...I have (what I call) a "2nd Generation" HEI. Whether it's truly
the 2nd version of the HEI, I'm not sure, but it's the 2nd version I'm
aware of.
This one is *supposed* to use a 5-pin module. It has 2 pins on one
side for the condensor to connect to, but the other end has 3 pins,
rather than just a G and W. That end connects to both the pickup coil
as well as the external ESC/ECM. The connection that comes from the
pickup coil has 3 pins of course, only 2 of which go to the coil. It
has both female and males ends, and functions as a "pass-through"
connection (that's what I call it). This basically just allows the ESC
connection to piggyback onto the module after the pickup coil is
connected.
If I hadn't messed with that connection, we wouldn't be having this
conversation. I had figured that a 4-pin (1st generation...no ESC)
module would work just fine in this distributor, despite the fact that
the pickup coil connection was different. But because of the spacing
of the pins in that connector, it wouldn't work. So I used the
smallest flat-head precision screwdriver I had, and pushed the metal
tabs down to slide the metal pins and wires out of the connector
housing without damaging them or the housing.
I blew out my 4-pin module, as well as two 5-pin modules, because I
didn't have the internal ground wire connected to the ignition coil. I
thought when I reassembled that connector (to try out the 5-pin
modules) that I reassembled it correctly. I apparently did NOT :-)
As it is, the ESC is disconnected, and although I'm using a 5-pin
module, it functions as the earlier, 4-pin version of the HEI. I ended
up using the ESC connector that piggybacks onto the pickup coil
connection and removing the center wire, then ran a short wire between
pins 1 and 3. That way there's no external harness coming out the back
of the distributor. I could've used female blade connectors and
accomplished the same thing. In fact, that's what I plan on doing when
I document the process for others to see.
I have a spare HEI of the same vintage as mine, so I'm going to be
taking some pics of the whole modification procedure to post on my site
for others to see.
~jp
SnoMan
wrote:
>I can usually figure out the problem given enough time and a few decent
Feel free to post a article about it on my site/forum to if you want
too. I will remember this one too as I had never seen if before either
(as I mentioned earlier). On a side note, unless you have a large
overlap/aftermarket cam, the vacum sounds a bit low at a idle (from
what you stated) .
-----------------
The SnoMan
www.thesnoman.com
aarcuda69062
<1148384686.0...@j55g2000cwa.googlegroups.com>,
"Jon R. Pickens" <jonr...@gmail.com> wrote:
I hadn't realized that you had modified the harness to the
ignition module, I was under the impression that someone had sent
you the distributor wiring that burned up in the fire and that
all you had done was jumper the 4 pin ESC connector to by-pass
the knock control.
I'm very familiar with the by-pass modification, was doing them
20 years ago in the dealership. Fastest way was to pull the
glove box down and cut the green and black wires and splice them
together. Neat, clean and protected from the elements.
Of course, this assumes everything forward is in tact.
I should have had you send me some pictures of the open
distributor, things would have progressed much faster.
Anyway, it's fixed and now you can move on to the transmission
leak. That rates an atta boy!
aarcuda69062
"The Jones'" <rjone...@sc.rr.com> wrote:
The pick up receives no signals, it outputs an AC voltage to the
ESC box under the dashboard, the ESC buffers the signal from the
pick up and sends it back out to the ignition module, when the
ESC box receives a knock signal from the knock sensor, it
modifies the buffered signal, retarding the timing.
By having the pick up wires reverse polarity, he altered the
shape of the AC signal from this;
/I /I /I /I /
I / I / I / I /
I/ I/ I/ I/
To this;
I\ I\ I\ I\ I
I \ I \ I \ I \ I
I \I \I \I \I
Since the module triggers on the falling edge of the pick up
signal, as RPM increased, the peak to peak voltages went up and
as they did, the trigger point retarded.
Good lesson on reactance and reluctance...
(apologies if my ASCI art doesn't turn out.)
Jon R. Pickens
> too. I will remember this one too as I had never seen if before either
> (as I mentioned earlier). On a side note, unless you have a large
> overlap/aftermarket cam, the vacum sounds a bit low at a idle (from
> what you stated) .
Well, the cam is stock to the engine, but as I stated earlier, the
engine (290hp) is the same as the 260hp motor, with the exception of
the cam.
Here's the cam specs: ".450'' intake and .460'' exhaust lift", and
"Flat Tappet Duration @ 0.050'': 222° I, 222°"....per the Jegs site.
I was never able to get a lot of vacuum on this engine. With
everything plugged, and the timing and idle circuit set to max vacuum,
I was able to get 16" Hg once, but that was only because I was trying
to achieve max vacuum, not because it ran best that way.
What's sad is, after all this, I can now tell that the engine is
running rich as ever, at least at idle. No idea how the smaller jets
will affect the cruise and power mixtures yet.
I'm about to throw this carb off a cliff and get another Quadrajet...
Eh, I won't do that. But the TBI swap is looking *mighty* good.
I'll post the info on your site once I've got photos taken. May not be
this week, as I got packing and moving to do, but next week at the
latest probably.
~jp
Jon R. Pickens
> ignition module, I was under the impression that someone had sent
> you the distributor wiring that burned up in the fire and that
> all you had done was jumper the 4 pin ESC connector to by-pass
> the knock control.
I wasn't able to locate one. I found the big connector going to the
firewall at Pep Boys and the internal connector that went to the module
was ok, so I made a new one from scratch. I never was able to make it
run, but again, when I was using that harness I still didn't have the
ground wire connected to the coil, so it was futile.
> I'm very familiar with the by-pass modification, was doing them
> 20 years ago in the dealership. Fastest way was to pull the
> glove box down and cut the green and black wires and splice them
> together. Neat, clean and protected from the elements.
> Of course, this assumes everything forward is in tact.
Yeah, I know it could be done pretty much anywhere... I just chose to
do it internal to the distributor and eliminate the harness out of the
distributor altogether. Looks cleaner. I do plan a TBI swap at some
point, preferably sooner than later. The Edelbrock carb just runs way
too rich and I'm sick of screwing with it. It makes NO sense, but I'm
almost to the point of giving up.
The big grommett on the firewall that went to the ESC will eventually
be used to run to the ECM once I do the TBI swap.
> I should have had you send me some pictures of the open
> distributor, things would have progressed much faster.
Yeah, probably... I was running myself in circles. The missing ground
wire caused me to kill 3 ignition modules before I caught it. By that
point I wasn't even thinking about the polarity of the pickup coil
wires.
> Anyway, it's fixed and now you can move on to the transmission
> leak. That rates an atta boy!
Yep...calling Mr. Transmission before lunch to talk to the mechanic and
set up the deal. If everything goes as planned, I'm gonna get it towed
out there today, and it'll be rebuilt by Friday.
Then I can start chasing down TBI parts and gear up for more work
<sigh>.
~jp
HDS
"redeye-racing" <redeye...@hotmail.com> wrote in message news:1148366274.0...@u72g2000cwu.googlegroups.com...
>i skipped through some of the posts..lots to read...i don't know if
> anyone mentioned this and i don't know if it's relevant...i came across
> a similar situation a few times on 88-94 chevys...HUNTING
> timing..timing moves all over...some times runs ok till your on the
> gas, some times idles bad...the rector wheel with the magnets on it,on
> the distributor shaft was loose, and spinning on the shaft...
Yea, been there.
I advise everyone with the 88-95 V8 chevys to dump that distrib and get the
"Ready to Run" MSD distributor instead. More than worth it.
MSD-8366 Chevrolet/GMC: 1987-93 cars and 1987-95 trucks
HDS