Fuel pump woes

[Clod_King]

So my fuel pump doesn't like to kick in right away...

I have to crank the engine over for like a 30-45 seconds before the fuel pump kicks in, and the engine finally starts.


But when the enigne has been run for a while, and is warmed up, then the fuel pump sometimes doesn't want to kick in at all! I have to wait around for the engine to cool right down before I can get the stupid fuel pump to work


There are brand new fuel lines, and filter, and the sending unit, and pump are new units aswell....

What could be my problem??

 

[George_Pimpdaddy]

this is on a tbi truck im guessing well might be a bad connection or even relay on the firewall. usually you can hear the pump whine when you first trun the key on.

 

[Clod_King]

Yeah I can usually hear the pump kick in after a little while.

That's how I know when the truck is refusing to start, because if I don't hear the whine after a while, I go for a walk and wait for the truck to cool down.

I want this rig to be more reliable. I'll try the fuel pump relay, and if it doesn't work I'll be back on hear...

 

[dyeager535]

Put power to the red wire hanging off your fuel pump relay. I'm guessing your fuel pump relay is shot, and your oil pressure switch is flakey, or you have really bad engine oil pressure.

 

[Clod_King]

well the il pressure guage says I have a good amount of pressure (right in the center of the gauge most of the time).

Well I got stranded again today so I popped the hood and beat the crap out of the relay....

The engine started after that. But I still have not located a new relay. I tried a few places, and they didn't have anything

I am gonna make some more calls.

 

[dyeager535]

My point was, don't waste your money. Put power to the red wire when it's acting up, if it starts and runs like normal with power to the wire, your relay IS the culprit.

Although beating on the relay one time seems to have "solved" the issue temporarily, it very well could have been a coincidence.

If you've got any, just go to a wrecking yard and grab one, (ok a couple, spares if all are good, or confirmation it's not the problem if multiple don't solve the issue) if that's possible without getting hypothermia. Tons of those things out there, and they are actually quite durable. I haven't purchased a new one yet, and am running something like 5 of them.

 

[Clod_King]

So I bought a new one because it was only 13 bucks, and the wrecking yards around here aren't the best... And the biggest one around (20 minute drive) stopped do the pick n' pull.

But even so I changed it out, and the problem is still there.

You were right the first time. My gauge reads zero during start up (oil gauge). And the engine only starts when the gauge hit 200 kpa (30 psi)....


So what would cause the oil pressure to not be there immediately??


I am geussing the computer is not letting the engine start until the pressure is up, but why would the oil pump be working as soon as the engine starts cranking??

 

[dyeager535]

You might have an electrical problem. You won't get much pressure until the engine starts, sounds to me like you've got a ground issue or something.

 

[Clod_King]

How would I find that out??

Plus I the time it takes to get the engine to turn over varies, but the engine will ALWAYS start once it hits the 200 kPa mark. Sometimes a little beofre it...


Would it show up in the engine codes??

 

[dyeager535]

Nope, the ECM doesn't care about oil pressure, and does NOT monitor it.

I'm sure it's nice and warm where you are now, so no problem going out and playing with all this right?

Did you do the relay bypass test?

 

[Clod_King]

ummmmmm.......... nohahaha.

Yeah it's shorts weather out right now, hahaha. We actually just had like a foot and half of snow dropped on us too....

I'll do the bypass test tomorrow.

But the PO had the fuel pump set up with a primer button. You'd press and hold it for a little while, and then the truck would start right away after that.

Isn't that the same thing as hooking up power directly to the red wire on the relay??

 

[dyeager535]

Maybe, maybe not. You need to remove that as well, and make sure every trace of the wiring is gone.

 

[driney]

Check if there is 12 volts on the dark green/white wire at the relay right after you turn the key on. I think that is the right one. It is the wire from the ECM that closes the relay. There should be 12 volts there for a couple of seconds. It sounds like nothing is starting the fuel pump until the oil pressure switch closes.