ALMOST THERE - Fuel Shutoff Solenoid Issue - M1028

[Bravo2Uniform]

1986 M1028. Purchased a few weeks ago, using as a farm truck, I need it badly right now, we are harvesting. I have previously owned an M1009. This unit had a snow plow on it and there are tons of extra wires running to and fro. I have removed as many as possible but they seem to reproduce or something.

Driving on interstate when it just shut down, no warning, nothing, just lost power. Found that I could run a wire from the glow plug relay to the pink fuel shut off and get it to start and I got home. I am thinking the issue is a short in the pink wire as I saw some evidence of chaffing / naked wires in one location.

From circuit diagram E-3 I see the pink wire (3 PNK - 3 (SXL) runs from the fuel shut off to a fuse block. Here's where I'm embarrassed - where is that fuse block?



Is it possible (I know, anything is possible except skiing through a revolving door) that this is as simple as running a new wire if I could find the elusive fuse block?

 

[Rutjes]

Looking at the wiring diagram it should go to the fuse box located above the pedals? Fuse 15? Fuse 17 is also part of that circuit?

 

[Bravo2Uniform]

Looking at the wiring diagram it should go to the fuse box located above the pedals? Fuse 15? Fuse 17 is also part of that circuit?

Thank you for the reply!

I believe you are referencing the main fuse panel. I verified all my fuses are good, so there's something in between the fuse panel and the fuel pump shutoff solenoid.

 

[nyoffroad]

Thank you for the reply!

I believe you are referencing the main fuse panel. I verified all my fuses are good, so there's something in between the fuse panel and the fuel pump shutoff solenoid.

Fuses may be good, but are they making contact? Also that fuel solenoid has to go thru the ignition switch, (before or after fuse IDK) . I'd start with the pink wire itself and check for voltage at that corroded spot first. Good luck, electrical gremlins can be a PIA!

 

[porkysplace]

Thank you for the reply!

I believe you are referencing the main fuse panel. I verified all my fuses are good, so there's something in between the fuse panel and the fuel pump shutoff solenoid.

Could be corroded in the harness that plugs into the fuse block, is there power on both sides of the fuse ?

 

[Curtisje]

I had the same thing happen to me once. My problem was corrosion at the end of the pink wire at the connection to the fuel shut off. I trimmed back the wire until there wasn't any sign of corrosion and then crimped on a new connector. No problems since then. Good luck.

 

[Bravo2Uniform]

Fuses may be good, but are they making contact? Also that fuel solenoid has to go thru the ignition switch, (before or after fuse IDK) . I'd start with the pink wire itself and check for voltage at that corroded spot first. Good luck, electrical gremlins can be a PIA!

I replaced the fuses today. I ran a new wire (temporary) from the wiring harness bulkhead plug to the fuel shutoff. No change in condition.

 

[Bravo2Uniform]

I had the same thing happen to me once. My problem was corrosion at the end of the pink wire at the connection to the fuel shut off. I trimmed back the wire until there wasn't any sign of corrosion and then crimped on a new connector. No problems since then. Good luck.

Thanks, I tried that after I read your post. Didn't work for me. However, I think this is telling me the problem is from the bulkhead to ignition switch route.

 

[Bravo2Uniform]

Progress Update:

Verified voltage on batteries.
Verified voltage on fuel shutoff (0 volts - but when a jumper is ran from to fuel shutoff it will pump and truck will attempt to start)
Ran wire from bulkhead wiring harness block to fuel shutoff. No change.
Clean and applied dielectric grease to all electrical contacts I came across.
Changed all the fuses and verified the contacts from the bulkhead wiring harness block to fuse block are good. Looks grody but seems to be okay.
Scratched my head and made several remarks about the marital status of GM engineer's parents prior to their conception.

I keep coming back to the fact that nothing happens when I turn the key - unless there is a jumper from the glow plug solenoid to fuel shutoff. Truck will attempt to start but cannot because glow plugs are not active. I just don't understand the theory of the starting system enough to connect the dots.

 

[Rutjes]

Sounds like everything under the hood is OK. Can it be that your ignition switch is going bad? Or the wiring between the ignition switch and the bulkhead. Time to crawl up under the dash and get some readings there?

 

[Bravo2Uniform]

Sounds like everything under the hood is OK. Can it be that your ignition switch is going bad? Or the wiring between the ignition switch and the bulkhead. Time to crawl up under the dash and get some readings there?

Good idea. I pulled the dash and instrument cluster last night. I was going to replace the bulbs anyway ( I like to be able to see my gauges in the dark, I'm funny that way). It occurred to me that I should try to induce a current along the fuel shutoff wire from the key to shutoff solenoid - that's a simple way locate the short. Simple process of elimination.

 

[Bravo2Uniform]

When you troubleshoot make sure you don't get fixated on the idea that a certain thing is wrong - you might be wrong and waste a lot of time.

I searched and searched and traced the fuel pump power. Never could find anything wrong. Out of frustration, I replaced the ignition switch - good thing I'm not a football player because that Hale Mary did not save the game.

Finally, it occurred to me that there were too many other systems dead for it to just be the fuel pump power. Sure enough, I found a burnt wire on the engine wiring harness block. Repaired and now I have power to my gauges, glow plug controller, etc. Previously turning the key produced nothing - it was like the batteries were not installed. Now it preheats and turns over.

I have not been able to get it to start - possibly the batteries are weakened by cold and sitting there for 6 months. Well at least she turns over!

 

[MarcusOReallyus]

I found a burnt wire on the engine wiring harness block.

That was probably a fusible link, not a wire, and if you replaced with wire, you now have a fire hazard of the, "burn your truck to the ground", variety. Please review the Fusilbe Links 101 in the "Helpful Threads" sticky at the top of the forum.

I have not been able to get it to start - possibly the batteries are weakened by cold and sitting there for 6 months. Well at least she turns over!

Yeah, it's got to spin quickly to start. :cheers:

 

[Bravo2Uniform]

That was probably a fusible link, not a wire, and if you replaced with wire, you now have a fire hazard of the, "burn your truck to the ground", variety. Please review the Fusilbe Links 101 in the "Helpful Threads" sticky at the top of the forum.

Uh, negative Ghost Rider - it was the wire not the fusible link. The wire section in question had rubbed the firewall to failure. Fusible link intact.

 

[Bravo2Uniform]

cheers

Yup. After sitting for 4 or 5 months plus that final two hour drive with no recharge the batteries were pretty weak. I'm just happy to have found the short. Gracious day in the morning that was tedious.