Would a bad ballast resistor cause an 86 F250 not to start?
ussho...@yahoo.com
I have a 1986 F250 7.5l 460 engine with the Duraspark II
ignition system. Would a bad ballast resistor cause my truck to not
start at all? It turns over fast but never even tries to start. It was
working fine and then I started messing around with the wires because
my tach stopped working.
I connected a volt meter to the BAT connector of the coil and the
block. I turned the truck to the RUN position and got 11.89 volts (book
says I should get 6-8 volts). With the way this thing is wired I can't
figure out how to test the ballast resistor by itself. Also, I connect
an ohm meter to the BAT and TACH connectors of my coil (with nothing
connected to it) and get 0 ohms. My book says it should be between .8 -
1.6. So maybe my coil and resistor went at the same time?
Any help is apprecaited.
Thanks,
Sam
Mike Romain
I would be looking for power on the coil positive when it turns over
next if you didn't already show 0 across the blown coil....
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Aug./05 http://www.imagestation.com/album/index.html?id=2120343242
(More Off Road album links at bottom of the view page)
ussho...@yahoo.com
parallel with the power cable. So in other words, I could cut off the
ballast resistor and there would still be power at the coil....
Sam
gobroncos
Mike Romain
to ground though, normally I see them inline so when they fail, there is
no voltage. One 'could' go to ground to steal some voltage too I guess,
I just have never seen them that way.
For the inline ceramic ones that fail, you can just put the two wire
plugs together to give you a full 12 volts.
I was under the impression that an 86 Ford has the same ignition as my
86 Jeep which has a ballast wire, not a ceramic resistor block. The
power when the starter is turning comes direct to the coil via the
starter relay bypassing the ballast.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Aug./05 http://www.imagestation.com/album/index.html?id=2120343242
(More Off Road album links at bottom of the view page)
ussho...@yahoo.com
"second" connection which drops the whole circuit down.
ussho...@yahoo.com
It did appear to be the original coil from 1986 so I got my use out of
it.
Stephen H
How many volts does your coil need to run?
Not 12 as you would assume, but about 10v. When you turn the key to start
the vehicle, the starter draws so much current that only about 10 volts is
left. so the engineers built the coil to a 10v specs (put a voltmeter on
the pos of battery and then the hot of the starter, and crank it with the
dist disabled--- about 10-11 volts
Now the vehicle is running and the 12 volts is at the coil-- enter the
ballast resistor, it uses up the 2 volts so the excess voltage doesn't burn
up the coil
I learned this last summer.
most all cars today only use 10 volts at the coil still, the ecm can
regulate some cars,
--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist
http://autorepair.about.com/cs/troubleshooting/l/bl_obd_main.htm
http://www.troublecodes.net/technical/
"gobroncos" <jimw...@aol.com> wrote in message
news:1135459855.2...@g47g2000cwa.googlegroups.com...
aarcuda69062
<Xcpsf.366182$zb5....@bgtnsc04-news.ops.worldnet.att.net>,
"Stephen H" <hans...@hotmail.com> wrote:
> OHHHH I know this one:
<snip>
> I learned this last summer.
Good grief, from who?
> most all cars today only use 10 volts at the coil still,
Actually, the cited 86 Ford F-250 w/ Duraspark ignition is one of
the rare examples in the last 20 years.
> the ecm can
> regulate some cars,
Shakes head in amazement....
N8N
ussho...@yahoo.com wrote:
> The case of the resistor is grounded which I am guessing is the
> "second" connection which drops the whole circuit down.
Are you sure that's a ballast and not a RFI suppression capacitor?
nate
Stephen H
>
> Good grief, from who?
>
>> most all cars today only use 10 volts at the coil still,
>
> Actually, the cited 86 Ford F-250 w/ Duraspark ignition is one of
> the rare examples in the last 20 years.
>
>> the ecm can
>> regulate some cars,
>
> Shakes head in amazement....
Don't remember the class sponsor; was basic auto electronics class. The
instructor put a Volt meter on a 5.0 test eng and showed us.
I'll have to look for the book. Was rather amazed when I quizzed my
father-in-law about it and he knew the answer but not the why.
aarcuda69062
<HlIsf.201681$qk4....@bgtnsc05-news.ops.worldnet.att.net>,
"Stephen H" <hans...@hotmail.com> wrote:
> Don't remember the class sponsor; was basic auto electronics class.
Was the class free or did you pay to attend?
> The instructor put a Volt meter on a 5.0 test eng and showed us.
I suppose it would depend on where the instructor connected the
volt meter. If he connected to the negative side of the ignition
coil, then yes, I'd expect to see some fraction of system voltage.
At the positive side of the coil, odds are that you'd see full
system voltage.
GM went this way in 1975
Ford went this way with the intro of TFI, basically around 1984
with the exception of carry over DuraSpark ignition used on HD
truck applications and police cars thru the late 80s early 90s.
ChryCo went this way around 1988 or so. Earlier on some models.
Can't think of a single application offered in the last ten years
that doesn't feed full system voltage to the positive side of the
coil.
> I'll have to look for the book. Was rather amazed when I quizzed my
> father-in-law about it and he knew the answer but not the why.
Not sure what the question was...
The reason for a resistor in the ignition primary is to control
current thru the coil primary. The anecdotal observation is that
it also drops the voltage to the coil, but voltage is more or
less meaningless until you have electrons flowing (current).
Bear in mind, when the magnetic field in an ignition coil
collapses, there is upwards of 300 volts induced into the coils
primary windings. Knowing that, what difference could a few
volts (10 vs. 12 vs. 14.5) make? None of this obviously should
ignore the fact that voltage to the coil can fall too _low_ and
affect spark output.
Stephen H
attending.
The test engine had sensors from all sorts of engines wired up to it, the
instructor could hit a few switches and cause all sorts of problems to
happen. Great learning experience.
Restriction on the fuel filter? fuel pressure maintained constant, amps
increased and volume decreased. It was good to SEE the cause and effects of
problems on the car.
We did a voltage drop test one test lead on positive of battery and one on
the hot of starter. Great tool for diagnosing many problems on a car.
The instructor also did something to demonstrate the 10v system on the coil
as it related to starting, but I don't remember exactly what at this time...
Gust had another class on Volumetric efficiency in an engine and diagnosing
the total fuel trim problems. (How much effect does a rear o2 sensor have on
fuel trim...) That one flipped my learning around.
Got to find that book
I'll now try to dig up the book with the wiring diagram; it showed 12 v
through the starting circuit to the coil and a separate line going through a
resistor to the coil hot for running.
If the coil stays with a constant 12 v while running than the chances of
killing a coil (primary side) from heat are much greater.
Take care
--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist
http://autorepair.about.com/cs/troubleshooting/l/bl_obd_main.htm
http://www.troublecodes.net/technical/
"aarcuda69062" <none...@sbcglobal.net> wrote in message
news:nonelson-B7FEEB...@newsclstr02.news.prodigy.com...
Mike Romain
dependent on the coil.
My 86 Jeep has the old Ford ignition and I bought an Accel SuperCoil for
a hotter spark. The Accel coil can run on either a direct alternator
power level or use a ballast system.
I asked Accel about using it hot (14+ Volts) for the hotter spark and
they told me if I did I would cook the ignition module. It even warns
about that on the Accel site.
You saw one old test engine. That does not translate to 'all' coils.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Aug./05 http://www.imagestation.com/album/index.html?id=2120343242
(More Off Road album links at bottom of the view page)
Stephen H
Modern cars still do reduce voltage to the coils, mostly in the ignition
modal if I remember correctly.
The critical point being that during a start, the car pulls the available
battery voltage down to 9-10 volts, and a full 12v coil wouldn't have enough
voltage at that time to saturate and fire correctly.
It applied it the old days and still today.
Every starter test we do shows 9-10 volts at start and the car passes with
that number.
--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist
http://autorepair.about.com/cs/troubleshooting/l/bl_obd_main.htm
http://www.troublecodes.net/technical/
"Mike Romain" <rom...@sympatico.ca> wrote in message
news:43B3F9F3...@sympatico.ca...
Stephen H
http://autorepair.about.com/cs/generalinfo/a/aa052502a.htm
http://finance.groups.yahoo.com/group/locost/message/49646
Still looking for better references, this was just a quick search
Steve
aarcuda69062
<y63tf.205056$qk4....@bgtnsc05-news.ops.worldnet.att.net>,
"Stephen H" <hans...@hotmail.com> wrote:
> the engine wasn't that old, perhaps 7 years F.I.
Not so much a question of age or fuel system, it's a question of
what exercises that particular simulator was designed to emulate.
> Modern cars still do reduce voltage to the coils, mostly in the ignition
> modal if I remember correctly.
They most certainly do not.
Don't take my word for it, pop some hoods and do some testing
with your voltmeter.
Better yet, use a lab scope, that way you can see all the
dynamics over time.
> The critical point being that during a start, the car pulls the available
> battery voltage down to 9-10 volts, and a full 12v coil wouldn't have enough
> voltage at that time to saturate and fire correctly.
Problem is, coil saturation is not a function of voltage, it is a
function of current.
> It applied it the old days and still today.
> Every starter test we do shows 9-10 volts at start and the car passes with
> that number.
Yes, and modern e-core style coils will output enough secondary
when fed 9-10 volts to start an engine, especially now that we
have advanced fuel control and delivery.
Going back to the original post; the Ford Duraspark system in
question will actually shut itself off when cranking voltage goes
under 10 volts. You can demonstrate this for yourself by
connecting your carbon pile to the battery terminals, installing
a spark tester on the coil wire, cranking the engine (remotely)
and adjusting the carbon pile during crank. At almost exactly 10
volts, the spark will go out.
aarcuda69062
<Rp3tf.205101$qk4.1...@bgtnsc05-news.ops.worldnet.att.net>,
"Stephen H" <hans...@hotmail.com> wrote:
Amazing how many get this stuff wrong.
Hell, I bet I can find ten times as many articles that state that
oxygen sensors measure oxygen in the exhaust, (they don't) but
you can bet your next paycheck that [that] is the way it is still
taught.
About 20 years ago, I made similar statements in a GM specialized
electronics training class. The entire room went silent. (not a
good thing)
Thing was, of the eight of us in that class, five were full time
GM instructors**, the other three of us were dealership line
mechanics. I got a very good lesson on how an ignition system
works that day, a lesson I won't ever forget.
** the five were;
Bob Bendixon
Perry Days
Don Fritz
John Porter
some black dude from Detroit who's name I forget cause he was the
only one not from Milwaukee.
the instructor was Roger Hassler.