geoduke

My truck sat for a couple of years before I could pick it up and get it back to my place again. Since then, I'm not able to get it to start.

It cranks. It has spark. I ran a cable straight from the battery terminals into the fuel pump wires and I can hear it run and it spits fuel out of the banjo bolt on the fuel rail if I have the bolt removed.

I think it's a fuel issue in getting the pump to run during normal operation. I tried jumpering between the Fb +B and I am NOT hearing the pump run when the key is in the start position.

Is this a COR or fuel pump relay issue? The truck has spark so I'm not sure if that rules out the COR or not. I just don't know where to be looking in the electronics/relay side of things to get this running again.

Thanks!!

scope103

No. FP goes STRAIGHT to the fuel pump; no relays involved. There is no "fuel pump relay"; other, I guess, than the COR. If the EFI relay fails to close the fuel pump won't run, but you won't have anything else (spark, starter) either.

BUT: do you have 12v on B+? Easy first: the key has to be on for there to be 12v on B+. Then, put your multimeter on B+ to ground to look for 12v. Then check the resistance of FP to ground. Since you're certain the pump will run, if you get anything more than about 20ohms you have a bad wire from the front of the truck (FP) to the fuel pump.

No multimeter? No excuse for that! http://www.harborfreight.com/7-funct...ter-90899.html You have an electrical issue; trying to solve it without a multimeter is just blind-man's-bluff.

geoduke

Many thanks for the easy explanation.

I just checked and I'm getting 12v from B+ to ground. I tested it again with the jumper (FP B+) attached and it was around 9v. Not sure if that drop due to the jumper present is significant or not.

For resistance of FP to ground, I get numbers that bounce around quite a bit (15 to 170 ohms). What is FP to ground resistance checking for??

scope103

FP goes straight to the fuel pump (and then to ground). So measuring the resistance there should just be the resistance of the fuel pump (I don't know exactly, but probably in the 10 ohm neighborhood). When electric motors fail, they usually fail "open," giving infinite ohms. But you don't have that (you know the pump works), so what I was looking for was infinite ohms indicating a broken wire.

When you directly wired the pump, did you disconnect it from the harness? If there is a short to ground in the harness, that could give you "low" resistance to ground, enough to pull B+ to 9v, but deprive the pump of enough electricity to run.

OR, your pump could actually be okay, and you need to adjust your hearing aid. (9v is too low, but you might be running your battery down). DON'T remove the banjo bolts; every time (EVERY time) you do that you have to replace the crush washes. Instead, pull the fuel return line from the fuel pressure regulator, and run a 1/4" hose (I like clear plastic) into a fuel-safe container. As a low-pressure line, you don't need to replace anything when you do that. If the pump is working, you should get about 1/2 liter/min through the return line.

geoduke

Ok I think I'm understanding this a little more. The fuel pump wiring is pretty straightforward, all of the various relays everything passes through to get to that point was really confusing me.

It sounds like I can jumper from FP (or B+ for that matter) in the engine straight to + on the fuel pump. That will tell me if it's a wiring issue between FP and the actual fuel pump and I can dial in from there.

Cheers man!