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I am stumped. Need professional help

ktmoutfront

ktmoutfront

We live in the stupidest times.
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For those who have not been to the BB13 carnage thread, I am having ignition issues.

87 Jimmy all stock engine and controls.

Driving down the road, acted like it was loading up then died. Restarted and would sputter off of idle but got it moved out of drive lanes into a parking lot. Sputtered again and died. Started again but would barely run off of idle. Then quit. Nothing now.

This happened on the way to Moab.:doah:I am home now and working on it.

Things looked at and changed.

ICM
Coil
ECM1 and ECMB fuses
Distributor cap and rotor
New distributor with another new ICM, cap and rotor. Came as and assembly.
Map sensor
TPS
IAC valve
ESCM

I have power into the coil, but no spark and no injector pulse. Gauges everything else works.

What do I look for now?
 
Take a look at the wiring harness running across the rear of the engine and on top of the transmission bellhousing.

My Sons 91 had very similar symptoms and I finally traced to a wire inside the harness had rubbed through the insulation and shorted to the bellhousing. I pulled the dist cap to see better.

Something to try. Good luck.
 
Just found that the Purple and whit wire that feeds from the always hot side of the starter solenoid into C9 on the computer is not charged. The fusible link is powered on the body side. When I tried to charge said C9 position, the crank fuse blew in the fuse box.

I am calling for a short somewhere now.
 
Maybe your fusible link is broken inside the wire jacket and fussing with it made the conductors contact again near the break? I assume you checked continuity of the link when it wasn't running?
 
Intermittent wiring issues suck. My kids 91 issue was found as it ran then died erratically until each time it died I messed with the wiring harness in a different area of the electrical system til I found the short on the bellhousing.

Good luck.
 
Look at the wiring behind the dash going to the ECM. Remove the ECM and pull the wiring through the firewall so you can inspect it under the hood. I found some wires that got caught in, and damaged by the heater control cables.
 
Finally got some time to work on this. Truck ran, then just died. Got my other harness out. Cleaned it up. Tried to start it, no dice. Changed the wires between the coil and ICM. It fired and ran. Has not died, until I shut it off. We will have to see.

New issue is, disconnecting the timimng plug does not do anything. Used too. Acts like its not feedeing what it should. Timing is at 0 unplugged or plugged. ????
 
You'll have to check the other plug on EST/ICM to ECM. Check pins in EST, check pins in ECM, ohm wires from end to end. IF all that is good, with the history of bad wires and blown fuses/shorts, it could have fried the EST-ICM or ECM.

When you replaced the EST/ICM you did use a AC-Delco or Delphi unit right? Also used the heat disapating grease under EST/ICM? The screws through EST/ICM are grounds.

attachment.php
 
I have that schematic. AC-Delco. Used the white contact grease. Was hoping it was a ah ha moment and would be one issue. It does jump from 0 degrees to 9 degrees with a couple hundred rpm off of idle.
 
Depending on engine tempreture, with bypass dis-connected and timing set to 0*. Then reconnected it should be around 15 at idle. Now setting timing does set a Error 42. it needs to be cleared. Recheck timing with bypass wire Connected, codes cleared, idle timing warm stock chip should be around 15+. Not 0*

The EST/ICM will add timing when revved, bypass disconnected but should not be that little at that little RPM...
 
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