Non-FSD wiring issues?

[DaveHart]

SOMEBODY do some splainin' on the ignition harness and other non-PMD issues related to stalling. I posted to the stalling thread, but wanted some specific info on this particular problem so I started a new one.

I went through PMD failure at the end of last summer. Put on new FSD onto a cooler and left old PMD on pump. Added a new lift pump while we were at it.

Recently, its cutting off after hitting a bad bump, drop, or pothole, or getting into a construction zone, milled pavement, etc. Not a good time to loose it. It's also has had a "bump" for the past few years (since I've owned it) at a certain excelleration (neither PMD nor lift pump fixed this). Sometimes this kick can be too much.

Cranks right back up in neutral on the fly.

I've also noticed that the gauges will sometimes quickly fall and start responding again with little other or no response from the engine compartment. Its so fast, I'm sure it happens at other times when I don't even notice.

The worn wiring issue sounds like it could have promise. Is the harness easy to get to, or will I have to get the tools to pull the steering wheel? What should I be looking for so I can see if I can repeat this in the driveway?

After reading other posts, I went out and abused the ignition switch with no effect.

Thanks in advance!

[Hubert]

Sorry I can't explain the ignition wiring very well but think you are on to something and or food for thought.

I have read lots of people who recommend cleaning the grounds/battery leads and chasis to frame ground straps. Some add additional ground leads. This helps ensure good contacts and circuitry working properly. Also, look at overall wiring especially common circuits that feed from the ignition. Several circuits tie into common nodes. I once had a short in my trailering plug that powered my FSD thru my reverse lights and would allow truck to run with ignition turned off while in reverse and foot on brake.

I have had shudder on launch (5spd but not a clutch problem because I haven't changed clutch and its now smooth) and recently an occasional jolt or bump in the motor under acceleration and cruise control cresting a hill. I believe its probably the fuel solenoid going south. Fuel additives (lucas and others) have made the shudder worse when the additive is mixed rich. [Straight diesel runs good and a very light mix of additive is also good.] I try to run an all around additive product for maintance every 4 or 5 tanks and change fuel filter often. But I have ~ 120,000 miles and I figure the IP/Fuel solenoid is worn and its not metering the fuel as precisely as needed for smooth operation at low RPM or during fuel rate changes.

Since the fuel solenoid is driven by the FSD I haven't ruled it out but both are expensive to replace so I am living with the intermittent ghosts for now. Also its quite possibly some little short or a connection with marginal continuity.

Keep posting and replying with feedback and someone should reply with thier experience.

[damork]

I had a weak or poor connection once on my main bulkhead connector on the engine side of the firewall just in front of the driver's side. You could wiggle the wires and the engine would stall.

I've read where others have had chafing of wires where the wiring harness goes into the passenger compartment on the passenger side of the truck by the AC/heater area. You have to remove some hardware to get at it to check it out.

I also had to swap out an ECM (didn't require changing the chip) on my 95. I don't believe anything was wrong with it, but it was part of a warranty program and GM wouldn't give me a good pump until I bought the ECM and proved it didn't help.

Last suggestion is track down the grounds. Biggest culprits I have found are the battery terminals, the ground near the right rear valve cover which also holds the AT trans tube if you have an automatic, and one on the frame near the RH side of the turbo down pipe.

[bigmikestud]

The last post could have been my exact words........the freaky dash lights out/restart over bumpy roads. I'm on my 3rd FSD, the battery cables got rewired with monster size cables. New lift pump/OPS/filter, etc. and I'm getting stalling/hard/no start in rain. Anybody have experience with wet weather causing these problems? I'm looking for the schematic someone posted for ground locations to check.

[damork]

One last item that probably applies here. I too was getting nowhere after checking what I thought was everything, then someone mentioned the brake light switch which could afftect TCC lockup (it also has the TCC switch in it) and trailer wiring.

Turns out I had trouble when it rained and my trailer wire connections were a mess. Took all the wires out of the plug connection point, replaced it with a new plug and made sure there were no more paths for any kind of crossfeed. It starts and runs better than it has in a long time.