Truck dies in drive, 1, 2

[latvius]

Sorry I can't be of more help, I just know that sometimes I may not understand what the problem is but I can narrow it down by swapping out things. That's why I suggest the PCM, if it doesn't change anything you and prolly rule that out.

 

[fordgirl]

Welp, my computer did have a blown capacitor and was leaking. New computer is in and now the transmission code is gone but I have new codes 116 and 636 and still a crank no spark no start…

 

[latvius]

Have you checked your grounds to make sure they are good with no corrosion? Bar that you started with a running truck that died when put in drive and now the truck won't start. I would review all what was worked on and go over those things as it appears the problem was introduced when trying to fix the original dies in drive problem.

 

[fordgirl]

I couldn’t agree more, I've been checking grounds but I’ve probably missed some. Do you have a diagram showing where they all are?

I’ve narrowed it down to the ignition coil not getting the pulsing signal to spark. The ICM is getting the PIP and bench tested good and I even swapped it out with another ICM that also tested good with no change. Also, the tach is still flatlined and it will NOT start with Spout out.

I’m thinking bad ground or erratic/weak PIP signal.

Is there a specific ground that could have been disturbed during transmission work? It did initially start after the work a few times so it wasn’t immediate.

 

[latvius]

Not that I know of, usually you have the batt ground, a ground strap to the eng and frame then the fuse box area.

 

[fordgirl]

Ok, new plan to rebaseline everything. I am going to confirm no spark at ignition coil with an inline spark tester. Then I'm going to verify there is no switching signal sent to coil (test light on passenger side of coil connector and clipped to positive battery terminal). If no flashing, I'm going to test switching signal out of ICM by backprobing circuit #2 with black side of my LED tester and red hooked to positive battery. If it flashes I'll check wiring from ICM to coil for continuity. No flash I'm going to check ICM power by backprobing circuit #3 with multimeter and cranking. If voltage drops below 10V I have the issue, if not I'll test ICM ground by measuring resistance from ICM circuit #1 to battery negative. If >0.1 ohms bad ground, if not I'll still run drop test and if >0.2V bad ground. If I make it to bad ground I'm going to use a jumper cables to hook ICM heatsink fin on fender to negative battery and crank. If she fires up it's confirmed. If I make it through all this then I'll replace ICM (Again...). If that doesn't work (again...) Then I'm going to buyan oscilloscope and plot the PIP signal going to the ICM because what else could it be at this point.

Only thing I'm unsure of is power. If voltage to ICM drops below 10V while cranking where do I look next?

 

[Fellro]

I had a situation once where my 88 just up and wouldn't start. Similar behavior to what you describe. Turned out the harness grounded directly to the battery, and the wire that does it had come loose from the aftermarket cable end.

 

[fordgirl]

Well not sure how I messed up running my tests before…but I just reran the tests and had a good switching signal (and power) at coil with no spark off coil. I removed and tested the coil which showed 0.3 ohm on primary and open circuit on secondary. New ignition coil and she fires right up!