Truck stalled, wouldn't restart, then started fine hours later

[ShannonTxBurb]

Seems that the fuel pump relay system has failed. You're running the fuel pump from the oil pressure switch. No oil pressure = no fuel, engine dies.

In this case, perhaps a good thing.


Test fuel pressure.


Nope.

I cranked it until the oil pressure gage showed pressure, no start.

With the ignition on there is no voltage on either leg of the fuel pump fuse. The fuse is OK.

It looks like no spark either. What would kill the fuel pump and the spark?

 

[Supercharged111]

Wrong thread?

Dude you're the one who hijacked this thread, I was responding to the OP.

 

[ShannonTxBurb]

Dude you're the one who hijacked this thread, I was responding to the OP.

Ahh, sorry bout that.

 

[78Monte]

My 1994 had a problem where on a cold start it would fire right up and run perfect but once you reached your destination it would not start again unless I let it sit 12 plus hours, Then it would do the same thing.

When this happened and it would not start it cut fuel and spark also..

I first replaced the ICM.. no dice..

Next I pulled the distributor and right away noticed the gear spun with zero resistance and felt sloppy so I went and threw a duracrap one in there and problem solved..

The new Duracrap did have a bad ICM out of the box though.. It would start normal but about 30 to 40 seconds of running it would start to misfire and sound real lumpy for about 45 seconds then smooth out and run perfect..

Instead of pulling the whole distributor and returning it, I just replaced the ICM with a new one I had on hand and it has run perfect since..

 

[Schurkey]

With the ignition on there is no voltage on either leg of the fuel pump fuse. The fuse is OK.

(Based on 1991 service manual)
The fuel pump fuse gets power via a fusible link (CK) or the ECM B fuse (RVG). If the link or upstream fuse popped, you'd have no power at the fuel pump fuse.

It looks like no spark either. What would kill the fuel pump and the spark?

Since you don't have a C/K (Pickup), apparently you've got problems in the ECM B fuse or wiring; I bet that kills the spark, too.

Note that things are different with 4L80E transmission. You should verify your wiring based on your specific vehicle in the proper-year manual.

 

[FLJoe]

This is likely not the case for you, but it's worth looking into. I've had a fuel pump relay go bad that would cut out when it was hot. The truck would die like the fuel pump had just gone bad. A little while later it would start right up and run fine. I tried swapping the fuel pump relay with the headlight relay (or some other accessory one in the main fuse box under the hood) and I was back and running. Now I always carry a spare fuel pump relay in the tool box.

 

[ShannonTxBurb]

I found a video that showed the same symptoms, no spark and no injectors firing. It turned out to be a bad coil.

Tomorrow it's a new MSD coil and a new fuel pump relay for good measure. 385k miles and I've never replaced the fuel relay.

 

[Schurkey]

I found a video that showed the same symptoms, no spark and no injectors firing. It turned out to be a bad coil.

A defective pickup coil can do that. A defective ignition coil probably wouldn't kill the fuel injection.

If the defective ignition coil caused the ignition module to fail, the failed module could cause lack of fuel spray.

Tomorrow it's a new MSD coil and a new fuel pump relay for good measure. 385k miles and I've never replaced the fuel relay.

The common MSD coils are Communist Chinese high-failure junk. Find a Treasure Yard, and grab a used-but-good OEM ignition coil if you insist.

"I" would TEST the ignition coil before replacing it. An ohmmeter and a spark-tester would tell that tale.

For that matter, a voltmeter and/or ohmmeter and some jumper wires would tell you if the fuel pump relay is cooked. My guess is that you have no fuel pump because you have no power to the fuel pump fuse, but what do I know? (Post 25)

 

[Dariusz Salomon]

This is likely not the case for you, but it's worth looking into. I've had a fuel pump relay go bad that would cut out when it was hot. The truck would die like the fuel pump had just gone bad. A little while later it would start right up and run fine. I tried swapping the fuel pump relay with the headlight relay (or some other accessory one in the main fuse box under the hood) and I was back and running. Now I always carry a spare fuel pump relay in the tool box.

Yeah me too

 

[ShannonTxBurb]

Update, I took the battery out of the burb to let it charge in the garage overnight. I didn't get back to it for two days. When I put the fully charged battery back in, it started and runs fine. I didn't change anything else.

I'm going with, the oil pressure dropped to zero and the ECM shut off the voltage that feeds the ignition and fuel circuits. Long enough with no battery and the ECM reset. Sounds reasonable.