Car question (mech troubles)

[MajesticMoose]

A friend of mine has a 87 or 88 ford f-150 with EFI(just said that because i think there might be a carborated version). The thing won't start and we've determined that the fuel pumps(one in the tank and atleast on outside) are stuck on, even with the ignition completely off. Do you have any ideas as to what is causing this. It'd be nice to have a starting point when we start working on it tomorrow(technically it would be today) I'll do my best to answer any questions, but as it isn't my truck, who knows how helpful that'll be.

thanks,
m00se

 

[TrevorK]

If the fuel filter hasn't been changed in a LONG TIME it could stop the truck from starting...


Trevor

 

[Sluggo]

Welcome to Pandoras Box.

Unless you are POSITIVE that you have traced the problem to the part you mentioned, I would recommend that you take it to a professional.

The fuel pumps on newer fuel injected cars will stay on even after shutting off the ignition to keep the fuel system pressurized. The fuel injection relys on proper pressurization of the system to function correctly.

 

[MajesticMoose]

well, i can't see how that would cause the pumps to run continuously. I'm pretty sure that the engine is becoming horribly flooded but i don't knwo why its doing that.

m00se

 

[MajesticMoose]

sluggo: I know its the part i traced it to. The fuel pumps have been running continuously for 2.5 hours, it can't need that much pressure.

m00se

 

[JohnnyKnoxville]

Hmm this is weird because usually you get a no start from the pump failing not sticking on.Trace the fuel pump circuit for a stuck closed switch.Start with the roll over safety switch which should be under the pass. side kick panel.

 

[BigLance]

I'm sorry for your friend: It's a Ford

Good Luck w/ it !!!

 

[MajesticMoose]

is that the kind of switch that needs replacing?

m00se

 

[Soybomb]

None of the fuel injected cars I've ever been in keep the fuel pump with the key off for any reason. Go outside, turn your key to the run position, did you hear that hum for about 3 seconds? Thats the fuel pump bringing the system up to pressure! I'm not saying that other cars can't be different, I've just never seen a car that would keep the pump on all the time, or even know why it would.

Anyway, even if your pump is running all the time, it shouldnt be causing the engine to flood because the injectors should be closed. Are you positive that the fuel pump is what you hear running all the time? Maybe go back to it and unplug it just to be sure. You say both pumps, does the truck have like an in tank and in line one then? Unplug 'em both just to be sure. If that causes the pump to go off, I'd not suspect anything wrong necessarily with the pumps, but something in the ignition wiring. Perhaps the ignition switch (not the lock cylinder, but the actual switch in the dash or screwed to the column) isn't working right. Thats my best guess, it isn't actually changing the ignition state to off, etc. Does it even crank?

 

[Sluggo]

Soybomb I could very well be wrong, but I swear that I have been in cars that continued to run the fuel pump after shutting off the ignition. Maybe it never happened and I was in an alcohol induced haze but I'm pretty sure there were a couple of them. Not that it ran all the time, just for a few seconds after shutting off the ignition.

And I know you werent calling me out and saying I was wrong, I very well could be, but I still swear there were a couple. Maybe they were VWs and I just heard the cooling fan running.

 

[87horsepower]

Thats a new one on me. I've had them not turn on, but staying on is a little odd. I have to think it is an electrical problem causing it to stay energized. Don't overlook the ignition switch on Fords in these years. There was a major recall on them. It's a long shot, but something is keeping the pump on.

 

[perry]

Try here.

 

[MajesticMoose]

soy, i'm positive that's what is humming. It does have one in the tank (actually two since there are two tanks) and one in-line. I did unplug the in-line pump and it stopped. The engine will crank, just not start. Also how would i go about checking that switch? just unplug it to see if the pump stops?

Sluggo: I didn't mean any offense, sorry if you took it that way, but it doesn't seem likely to be building pressure. But then, you didn't have as much info as i did when you came to that conclusion.

BTW i just went and checked, the pumps have now been running striaght for no less than 3 hours!

m00se

 

[Soybomb]

First, I'd consider disconnecting the negative battery terminal so you don't have a dead battery problem tomorrow

I'm not sure where to go from here. If it cranks, then the igition switch has to be working in some part, I'd suspect that it isn't the problem then. I think next you'd need to start checking out stuff like looking for grounding problems, shorts, and check out all the "important" ignition wires that power the coil/coilpack/whatever, fuel pump, etc. Maybe a relay somewhere is sticking or something? If you can test fuel pressure close to the engine that would be something interesting to do.

I still think its wiring related. The fuel pumps getting weak could keep it from starting, but they are running non stop for some reason. I'd be tempted to say the two are related and that the pumps is fine. Have you checked for spark while its being cranked? Pull a plug wire off a spark plug and either hold it just barely away from a piece of metal like the intake or head and watch for a spark to jump when its getting cranked, or you can put an old spark plug in the wire and hold the bottom of the j to something metal and once again watch for a spark jumping the gap when its getting cranked. If you can establish that its sparking, then you know its gonna be fuel related or timing related. I'm betting you'll find no spark.

 

[Sluggo]

I never get offended

 

[Thegonagle]

There's probably a fuel pump relay that's stuck or melted closed somehow. Start pulling those relays one by one until the pumps stop. Definitely disconnect the battery tonight.

EDIT: I should add, the continuous pressurization in the fuel rail could cause flooding. Some fuel injectors might leak slightly over time (related to age and wear), but not enough to affect how the engine runs. To clear a flooded EFI engine hold the pedal to the floor while cranking until it catches.

 

[87horsepower]

As Garfang said, it may very well be just the pump relay. I would try that first.

 

[Soybomb]

Fair enough, but those have to be some pretty leaky injectors to flood the engine I'd think....

Anyway I'm going to bed for now, good luck

 

[RayH]

Check the fuel pressure regulator or fuel pressure regulator solenoid if there is one. I don't think you have to worry about a flooded engine because most efi systems run the gas in a loop back to the tank and divert fuel from the loop to run the engine.

If the pump wasn't working, I would say that the car might have been bumped from behind. I think some Fords have an autmotatic shut off switch on the fuel pump that needs to be reset if the car senses something like an accident.