1981 Cadillac 6.0L (368cid) 8-6-4 motor.

[Daniel Frey]

I am having trouble with mine, and I have discovered a dripping fuel
injector. Will be replacing it soon. My question is: Does this system use a
spark-waste method when it disengages the cylinder? (ie. do the non-firing
cylinders still spark.) I did the timing chain and am not 100% sure the
distributor is in the right place. Is the ECM doesn't cancel the spark for
the dead cylinder than this isn't an issue.

Thanks,

Daniel

[Jeff McDonald]

I believe this system stays on 8 cylinders until 3rd gear is achieved.
If you're not the original owner, look for a wire from the trans. cut to
make it 8 all the time.

Anyway if you're messing around with it in Park, I imagine you'd have
all 8....

Jeff
Daniel Frey wrote in message ...

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[Daniel Frey]

Yup at idle it works on all 8, at 25mph/40kph it tries to disengage the
cylinders... and the car lurches and almost stalls before the check engine
light comes on and returns to 8 cylinders, and stays on 8 until I restart
the car.

It was working fine till a couple of weeks ago... compression on the motor
is good, low cyl 143lbs, high 155lbs, and the others in between. I just gave
it a tune up (cap, rotor, plugs, wires, hei coil). It did manage to pass the
local emissions tests (barely!), and when I was purging some carbon buildup
from the engine I noticed that one injector was "sputtering" and dripping...
which explains the rough idle and presumably the 8-6-4 problem.

When I put the plug wires on I noticed that the diagrams in my Chilton's &
Haynes books didn't match (every cylinder is 1 position counterclockwise off
of the diagrams I have.)

Which is why I am wondering if the ECM for this model year is smart enough
to cancel spark for the disabled cylinders. I might be compounding the
problem otherwise. I have figured out the mechanical (neat!) and the
electrical except for the spark question.

Thanks,

Daniel

"Jeff McDonald" <elje...@pivotnospam.net> wrote in message
news:3ba6a...@corp.newsgroups.com...

[ray]

> When I put the plug wires on I noticed that the diagrams in my Chilton's &
> Haynes books didn't match (every cylinder is 1 position counterclockwise off
> of the diagrams I have.)
>
> Which is why I am wondering if the ECM for this model year is smart enough
> to cancel spark for the disabled cylinders. I might be compounding the
> problem otherwise. I have figured out the mechanical (neat!) and the
> electrical except for the spark question.
>
> Thanks,
>
> Daniel
>

wait a sec... I think we might be on to something... on a car
with a distributor, you can pull it out, turn the engine over, and
as long as you line up TDC you can put the distributor back in
with the rotor facing any which way - that's cyl #1. On most
cars, that would be ok, but if the computer is trying to drop
cylinders that might wreak havok.

(you said you did the timing chain - did the distributor come
out at the same time?)

Imagine:
1-8-4-3-6-5-7-2 Firing order (small block Chevy)
computer decides to drop 8 and 5, but the is actually
dropping 4 and 7. Now you have 2 cylinders with no
valvetrain motion, and 2 not firing at all.

Does it have a crank position sensor or??? to determine which
cylinders to drop?

(this might fall in the wild-ass-guess catgeory.)

Ray

[Jeff McDonald]

And how does one set timing, base timing, on this thing? Grounding
ALDL connector perhaps? Can the ignition module run itself, without
the ECM? It wouldn't then know it was "supposed" to drop cylinders.
An inductive timing light would tell you if plug wires were running
and which ones were dropped. How to safely get under the hood within
the parameters of its dropping cylinders is the question... Drive wheels
on
jackstands, (very) light load, 30mph, high gear?

If *I* were programming it, I'd stop the fuel and do that magical valve
opening magic, but leave the spark-- no harm done...?

IIRC, most of these systems were modified eight-all-the-time by
disconnecting
the 3rd gear signal many years ago due to technological frustration. Are
you maintaining this for its eccentricity and differentness? (Not a bad
reason :)

Jeff
ray wrote in message <3BA6D6C8...@yaktam.com>...

[Daniel Frey]

Hello,

It always drops Cylinders, 1, 4, 6, and 7. It's due to the solenoids
actually needed to disable the valvetrain.

When I did the timing, the distributor was out, and I *thought* I put it
back correctly... but I am not too sure.

What you mentioned below is exactly what I am trying to figure out. :)

If someone knows which cylinder is supposed to be at the left of the
TACH/BAT terminal on the distributor I would appreciate it... none of the
diagrams I have indicate this, and it is a HEI distributor.From the diagrams
I have it looks like it is off by one position (it runs now, I'm driving it
everyday!)

Daniel

"ray" <r...@yaktam.com> wrote in message news:3BA6D6C8...@yaktam.com...

[Daniel Frey]

Actually, setting the base timing is really easy, I have done it already...

There is a green plug right next to the distributor... unplug it, set the
timing, plug it back in. Took 2 minutes. Runs well, other than the stumbling
at idle and the 8-6-4 problems (which may be related.) I will be replacing
the fuel injector on the weekend (it drips and sputters...).

I will make this work again... if I can get another 2-3mpg it's worth it.

It was working until about 1 week before I transplanted the engine into
another Caddy the same year/model. The car I took the motor out of had a
switch that would interrupt the 3rd gear wire from the tranny. Didn't need
it though 'cause it worked fine. Maybe it knew it was going to be
transplanted? Dunno....

It's cool when it actually works... :)

Daniel

"Jeff McDonald" <elje...@pivotnospam.net> wrote in message

news:3ba6d...@corp.newsgroups.com...

[ray]

could you put a scope on the engine to see which cyls are actually
firing when it tries to drop the cyls?

[Daniel Frey]

Thanks Steve,

I actually posted a message on there at the same time I posted one here and
haven't got any responses yet...

Daniel

"Steve" <steve...@mindspring.com> wrote in message
news:8njhqtk7s2adrdn7f...@4ax.com...
>
> Daniel:
> Look for the cadillac mailing list on yahoogroups. It is known
> as the cml. the...@YahooGroups.com
>
> There are several people there with great amounts of knowledge on this
> system. They, like you, will try really hard to keep them going.
>
> Steve B.

[Daniel Frey]

I have a timing light that I could hook up to see if it is disabling the
right ones, if it comes down to it. I may have to try it this weekend.

Daniel

"ray" <r...@yaktam.com> wrote in message news:3BA91FBF...@yaktam.com...

[Daniel Frey]

Well, I finally figured it out. There was a missing fuse (BODY) and the wire
that was supposed to run to the ECM had a bad connection at the ECM. It was
flooding out in 4cyl mode and stalling, as it wasn't getting the correct
signal from the MDDA unit.

Just thought I'd let everyone know (it doesn't seem to use the spark-waste
method, I used an inductive timing light and the Electronic Climate Control
engine diagnostics to force it to run in 4 cyl mode to determine this.)

Thanks for the replies I have had.

Daniel

Daniel Frey <ssd...@telus.net> wrote in message
news:t5sp7.726$9j.7...@news1.telusplanet.net...