C15 help!!

Friend's older 379 (1994?) w/Detroit developed two similiar problems, about one month apart, about drove him nuts.
(1) Truck would start missing, quickly die, sometimes immediately restarting, other times not.
Cause = Wire harness plug from ecm partialy disconnected. Visually appeared to be fully connected, "hands on" check revealed loose plug problem.

(2) Truck would miss, recover, then die shortly afterwards.
Cause = Low coolant sensor plug # radiator partialy disconnected.
Eventually the truck would only crank with hood opened; shutting hood would put enough tension on wires to separate the two plug ends, thus killing the engine.

 

That almost looks like something us up with the ecm or the connections.

 

What I am thinking also Check your grounds and your EMC wires. Also check at the batteries there is a dedicated set of wires that feed the ECM power and maybe the connector from there is loose and if so that would cause an intermittent issue. I had the same problem with a 1997 379 and it turned out to be a freaking cracked connector looked whole but at times would loosen and break contact for a instant.

 

Did you ever figure out your problem?
There's a master fuse inside left frame rail beside left steer tire . 140 amps are here, like a pony panel in the house . Power to your ECM stems from here
( 1 of 3 such power supplies to the ECM)
Many times bad connections, broken and or decayed wires from years of road debris, cause intermittent problems with power continuity to the ECM
2nd power to your ECM is directly connected to the batterys. 3rd power is from the ignition circuitry. And remember, for each + there's a negative. Negative wires cause just as much, if not more, issues.
All the best .
P.S...my TPS was newly installed last year but never calibrated. Engine jerks rapidly at very little throttle at 50 mph. Time to get er calibrated...time isn't on my side, hence the ling delay.
Let me know..
Thx...

 

10 years later.....

 

M603 last seen Dec 12, 2008. Walter Cronkite was still alive the last time we seen this guy.

 

I have the answer because I deal with it on a regular basis.

Bad fuel. Water in tanks. It's everywhere! Take a flashlight and look in the tanks after it's been sitting over night. You will see chocolate milk slug at the bottom