Originally Posted by diggerrigger

Some more background on the parts cannon diagnostics by the previous owner. I remind everyone that I consider the PO an able mechanic. Like most of us, he is likely much better at mechanical things than electronics.

Hurt my feelings when I became aware that he had purchased a rebuilt PCM off the net and paid, I believe, over $700. My '86 truck's ECM was listed at Advanced for $150. The PO was pretty sure he was dealing with an able and competent supplier. I asked if his supplier had asked about transmission and calibration code. PO confirmed he had. But a few days later a120 pin unit showed up.

I knew he had sent it back, exchanging for a different unit. I didn't realize until the other day that this truck was a 60 pin. Remember, I was pleasantly surprised because I had a 60 pin breakout box.

What I'm getting at is maybe the PO bought from a disreputable vendor. Maybe the PCM is incorrect and junk to boot.

I know the truck doesn't always shift gears correctly so I wonder if there is a E4OD vs 4R70W issue. My truck having the latter. Were '95s mostly 4R70W equipped?

I also know the PO's wife is the one who went to AutoZone to pick up the first ICM (actually, the truck was her's, a hand me down from her father)

Originally Posted by diggerrigger

Before I submit this morning's findings, a quick acknowledgement of @AuroraGirl 's contribution s. Thanks for pointing to Steve83's at Supermotors. Tons of information there on OBS trucks and Broncos.

Not sure if you were suggesting I check the wiring to insure my truck has CCD wiring or if that was pasted content from Steve83. Regardless, I can confirm that the truck is CCD. Still don't know how to determine if I have the correct ICM.

And the problem with most all the ICM testing on the truck is it is aimed at diagnosing a no or intermittent spark. Problems I run into on factory step by step (fan of step by step) is three steps in and you need a dealer proprietary test harness. Then I'm left trying to comprehend exactly what they are actually testing and then figure a work around using t-pins and back probing connectors.

On to today's surprises. When setting up to test the key switch to start with S-wire disconnected I needed to get my spark tester where I could see it from the driver's seat. I substituted a longer plug wire in place of the coil wire. No current flow even if I tightened the tool gap considerably. Coil wire= 7000 ohms, plug wire= 14k ohms.

Not sure if I reported or even checked this before but with current flowing,when the coil (-) is grounded the current stops. Unground and it starts again... "Most" times. If I poke at the coil (-) I can get the current to stay off... Sometimes.Note, grounding using test light.Bizarre.

Other suggestions followed up on. The PIP and SPOUT both deliver voltage pulse you would expect, engine running. Back probed at ICM connector

Other unrelated news. We had a heck of a storm overnight and I was disappointed to see the PCM connector all wet this morning. What a stupid set-up. Getting ready to storm again, gotta go

Originally Posted by diggerrigger

The coil connectors are dirty but corrosion free. I've unplugged and replugged many times during this quest. I'm sure of good connections.

The grounds? I cleaned and shined every ground I could find except I haven't serviced the main cable connections at frame and block. I should. I have checked for non harness ground problems as well. Pick up module to distributor housing. Housing to block. Everything does show <1 ohm resistance back to the battery (-)

I would like to think I have the grounds covered but I can't be sure. Can you suggest where to look for any of those stealth, not easy to find ground points?

I can put my hand on every ground wire, splice, connector and ground lug on my '86 EFI... Blindfolded!

Originally Posted by AuroraGirl

.

also groundign the frame of the coil making it stop sounds like its a bad coil to me, personally

Originally Posted by Soup bean

I put this on every electrical connection I make. (Whatever brand you want).

Originally Posted by AuroraGirl

Originally Posted by diggerrigger

@Prototypemech
Do you have a trick to unpin the terminal from the connector? Can the lock tab be disengaged from the front?

Also, just cold and windy now. Wet is over. So, after reading back through what I've done and not done, l checked for the offending current with key on, distributor unplugged. No current.

Originally Posted by Prototypemech

No, I don't remember which way the de-pinning tool needs to be inserted. Interesting observation with the distributor disconnected. Without power to the PIP, it's obviously not gunna work, so I wouldn't expect any current. How much current are you seeing with the Distributor plugged in?
The PIP circuit also feeds into the ECU so it can modulate the spark output via the SPOUT wire, but it should be just an input circuit (listening), not a output circuit (signaling). Just just for funsies, you may wanna hook everything back up and disconnect the ECU to see if the high voltage still exist at the coil with the key-on. I don't expect the ECU connection will make any difference.

Originally Posted by diggerrigger

Is this capacitor a replacement for my truck s original?

Originally Posted by diggerrigger

@Prototypemech
Do you have a trick to unpin the terminal from the connector? Can the lock tab be disengaged from the front?

Originally Posted by Prototypemech

De-pin or cut the PIP wire.

Originally Posted by diggerrigger

Interesting development. With PIP de-pinned at ICM the current flow becomes rhythmically intermittent. On/ off cycle a few times per second. Re plug the PIP and it's back to a smooth, steady stream.

With the PCM unplugged we still get the steady current flow. Thinking about that now