Dwilsh

I know there are already threads with starting problems but mine are a little weird. So I am building somewhat of a cruiser/track truck, nothing crazy right now just getting the truck running again. I installed a fuel cell into the bed with a MSD fuel pump, wired it up and it works. New filter in stock location. I can crank the truck and the fuel pump will run (It's actually quite loud lol). I can crank it, it'll turn over but doesn't seem to be getting fuel. If I jump the pump and prime it it will start then die immediately. If I give it starting fluid it will start run for 10 or so seconds then die out. It is getting spark and has compression. I picked up a side job at O'reilly's a little while ago so the parts aren't an issue (the discount is nice too ). I was thinking the AFM but I haven't gotten a chance to keep the jumper for the fuel pump on and crank it. Just looking at possibilities could it be that the timing chain slipped? I am rebuilding the motor as soon as I see it run again. It was my grandfathers truck he bought back in '90 and it ran great until it sat for 8 years or so and got moisture in the fuel tank.

scope103

How did you wire the pump? If you just moved the wire from the stock pump to the new pump, then "starts, runs a few seconds, then dies" is the classic sign of a VAF-COR problem.

Dwilsh

VAF-COR? yeah i used the stock wiring harness. I guess the ECU doesn’t like that?

scope103

I don't think the ECU cares, but all the parts have to work. Here's how to diagnose such a problem: https://www.yotatech.com/forums/f116...-quits-312747/

You probably have the "older" diagnostic connector: https://www.4crawler.com/4x4/CheapTr...CheckConnector But I believe the circuitry is the same.

Dwilsh

Thanks a ton! I’ll report back tomorrow.

Dwilsh

Update: Truck will run with the jumper cable on the fuel pump diagnosis by the fuse box. Not sure if it matters but I haven't wired the "sending unit" part yet so that may have something to do but not sure yet... Will update when I have more time.

2ToyGuy

Just don't drive it with the jumper in. MAJOR fire hazard. The COR is there for an absolutely critical reason. It stops the fuel pump instantly the engine quits, like in an an accident. That way you don't have fuel pressure in the system, which could pour out a broken line. Deadly dangerous.
With the jumper in, the fuel pump just keeps running. Bad, bad, bad!

I believe the only portion of the fuel pump circuit the "sending unit" shares, might be the grounding for the fuel tank. A wire somewhere from the tank to the body, or frame. Maybe. I might be wrong.

Good luck!
Pat☺

scope103

As 2ToyGuy says, the sending unit doesn't have anything to do with the pump. Since the pump runs correctly with the jumper, it is very unlikely to be, say, a problem with a ground at the tank.

That's why you have a multimeter (you do have a multimeter, don't you? No excuse to not have one. https://www.harborfreight.com/7-func...ter-63759.html) Just follow the steps in the posting I cited. Be systematic; don't cut corners or you might miss something.

Dwilsh

Of course I have a multimeter lol that was one of the first tools my old man bought for me! I’ll do some testing tonight and let y’all know. I sure do appreciate the help.

Dwilsh

Truck runs!! I ended up replacing the AFM but it was only $80 so not too bad. Idles super high though, don’t know what’s up with that.