[Gary Harman]

I've determined the ECM is not receiving a distributor reference pulse from the newly installed Caldone distributor. Had replaced it because I thought that was the problem, of course it came with new pick up coil and module.

After replacing the distributor the engine started right up but shut down 4 hrs later and would not restart.

Does anybody have any tips for checking the four wire harness leading from distributor to ECM other than just a continuity check?

 

[ppi12x4]

Continuity is the checkout. Also check for crossed wires. Only other check is ripping the harness apart and checking visually.


I don't trust anything from cardone as far as I can throw it.

 

[Gary Harman]

Thanks for your help. I was afraid of that, opening up the main harness and peeling out all the wires in issue.

When you say crossed wires, do you mean two wires insulation worn and touching? I must have a short somewhere in the reference hi and low and bypass signal wires because I am not getting a spark. New coil too.

 

[ppi12x4]

Yes 2 wires touching.


Unplug the ecu, coil, ign module, and pickup. Check for continuity between 2 wires until you check them all.

I'm betting its a faulty part

 

[crankz1]

Working at the USPS, we service quite a few 2.5L based mail trucks.
The little wiring harness, inside the distributor, has a tendency to fail.

 

[Jacob L]

Working at the USPS, we service quite a few 2.5L based mail trucks.
The little wiring harness, inside the distributor, has a tendency to fail.

So where can you get one of those wiring harnesses?

 

[crankz1]

We get all our parts from Wheeler Brothers Inc. I don't know if they sell to the public.
I would imagine you could get it through a larger parts supplier like NAPA.

 

[crankz1]

Rock Auto ... Here

Edit: Well, that link didn't work.

Part number- 1989457 ACDelco

O'Reilly- BWD PT783

 

[Steady Eddie]

crank--

Welcome to the Forum..

Thank you for your post, part numbers and everything..good job.

Anyhow, your job puts you right at Iron Duke Central..

how are you now solving the "Made in
China" EGR valve problems??....

 

[crankz1]

lol All the stuff from Wheeler Brothers, that the post office buys, is junk from China!
And, that sucks! I mean, you put on a new part, you kinda expect it to work... Not always the case.
Surprisingly, EGR valves haven't been a common failure.
And, yes, we see thousands of 2.5 and 2.2 OBD1 vehicles.

Thanks for the welcome! New here, but not new to forums. However, I'm not much for the whole introduction threads. Anybody wants to know about me, just ask.
One little "about me", crankz1 is my license plate and stems from my owning and operating a machine shop called Federal Crankshaft in STL. One of the many things I've done in life...

 

[Steady Eddie]

crank--

So then, you know all about the Chinese-made junk..lol..

What are the common failures that you see??

 

[crankz1]

I don't turn wrenches there anymore. Been the painter for 7 years now.
Given the nature of the vehicles, and drivers for that matter, they get tore up!
Plus, the STL vehicle maintenance facility services over 3000 vehicles for the area. Anything and everything that can fail, has and will again.
Front suspensions and steering linkage, brakes, G80's, engines, trans, fuel pumps (lot of them)... You name it.
Can't really compare the mail trucks longevity with that of a passenger vehicle. The mail trucks are constantly getting put through hell.

 

[Gary Harman]

Yes 2 wires touching.


Unplug the ecu, coil, ign module, and pickup. Check for continuity between 2 wires until you check them all.

I'm betting its a faulty part

I'm slowly going through checking all wires, it's going to take some time.

I thinking now, as this is the third module to fail including the one in the new distributor.

Maybe a crossed wire is bringing 12 volts back to the module on either the white/ tan black stripe/ or purple white stripe wires.


Do you also know which wire is the tach terminal? My chilton manual keeps refering to it to check voltage on it.

Do you mind if I e mail you some correspondance and updates?

 

[ppi12x4]

I prefer to keep it on the forum. Possibly help someone else in the future.

I don't remember which wire is the tach signal but I can find it next time I have time

 

[max1million]

tach, white wire on coil that the distributor make/break to ground to cause coil to spark, it should be near 12 when not grounded and 0 when grounded, aka light blinks when cranking

tried wiggle test? intermittent faults can be a pain to track down

http://www.s10forum.com/forum/f106/2-8-no-spark-questions-462960/#post7335211
2.8 No Spark - wiring basically same as 2.5
http://www.justanswer.com/chevy/1bko9-1987-s10-wont-start-unless-pour-gas-down-throttle-body.html
1987 s10 wont start unless i pour gas down throttle body

 

[Gary Harman]

Thanks Max and ppi.

Gives me some good direction, Right now I'm confirming the ICM and coil are ok. Both are new. I checked 4 wire harness to distributor when key on and did not see 12 volts. So maybe receiving back voltage when something is switched on. Something is causing the modules to fail.

Gary

 

[max1million]

the 12+ from ignition switch pink is tied to the coil, and distributor,
reference to ecm also used for injector (it should pulse when cranking),
the 4 wire is to ecm (includes reference, none 12+ that i know of),
ground 0+, bypass 5+ when it is, ref and est pulse (1-5?),
should spark when cranking even with 4wire disconnected,
if coil has more then 10+ pink momentary ground white tach coil should spark,
mostly that's in those diagnostics charts, and diagrams
theres test for icm, pickup, hall effect, coil in there

just a bad connection can cause intermittent problems that you think you fix by changing something that had no effect, and you wiggle a connection in the process. if they're it's actually frying maybe an intermittent short (connecting where not supposed to, like cause of wear).

modules need to be mounted with heat sink compound so not over heat, coil shorting or high current, over voltage cause bad charging regulator cause higher current

 

[Gary Harman]

Max Million

Thanks for your continued help. Stills searching, now ready to open up main wiring harness. Have little time to work on this S 10 but I badly want to get it running.

Question. The white tach wire leading away from coil, not the one going to ICM. Where does this tach wire go to? This truck doesn't have a tach. Is there a tach terminal, is there a fusible link on this circuit?

I thinking now maybe I have a short to ground on this wire.

I put a pin through the insulation on this (white) wire to check volts. With key on I have 12 volts. to ground.

Next when I put 8 volts to p terminal on module and the 12 volts drops to .64 volts where my haynes manual says it should only drop to 7-9 volts.

That's how it's left right now.

Gary

 

[max1million]

Tach wire goes to tach circuit in instrument cluster, or not. Fusible link would be on the supply. White is getting 12v so it not shorted and fusible link is not open.

Don't know where it says 7-9. White tach should drop near zero when icm in distributor shorts it to ground, the the pink supply should stay near 12.

 

[88-s-10trk]

the 12+ from ignition switch pink is tied to the coil, and distributor,reference to ecm also used for injector (it should pulse when cranking)

Had similar problem earlier this year. You need to see if injector is pulsing (noid light) when turning engine over. That's what ended up being my problem, I had a broken injector wire and was not getting any pulse through the hall effect. No fuel pulse, and no spark pulse.