1990 F150 fuel delivery problem

On Sat, 11 Oct 2003 10:14:18 -0700, Brent Olson rearranged some electrons to form:

Your truck should have 3 fuel pumps, one low pressure pump in each tank, and a high pressure pump on the frame rail.

You should check the fuel pressure at the injectors, to make sure you're getting adequeate pressure. You may also want to check your fuel filter to make sure it's not stopped up.

It's a pressurized system. Leave the engine off long enough and the pressure drops off.

At a guess, somewhere between your tank switch and pressure sensor, there is a restriction in the line that delays the pressure build up needed to shut off the fuel pump.

Naturally, if you try to start it again right after it has been running or the fuel pump shuts off you still have pressure and it will start.

Simple test, get it running and warmed up. Take it out where you can cruise, get it up to speed then really dump it. If there is a restriction, the system won't be able to supply enough fuel to handle the load and the engine will let you know.

Good luck

Sounds like a good theory except for the small detail that his truck has no fuel pressure sensor. The pumps should run for a couple seconds when the key is first turned to the run position. After that it should only run when the PCM sees an input from the ignition pick up. Bob

Ok. I replaced the fuel filter last night, then went for a drive. I added some fuel injector cleaner to see if it'd help. I drove for about an hour on the freeway, switching tanks back and forth. There was no hesitation or anything on the freeway. The truck will do 70mph all day long.

This morning, I go out and turn the key and I hear the fuel pump run...and run...and run for about 4 minutes. I was beginning to wonder if it'd ever stop. It finally did, and only then would it start. I tried a couple of times during that four minutes, and it would not start. As soon as the fuel pump stopped, it turned over instantly.

So if it's the fuel pump, it'd be the high pressure one, as that's the only one in common with both tanks, right?

Last summer, I came out one day to take the truck out and noticed a slimy goo on the outside of the truck, heavily concentrated around the fuel fillers. I've read now that there was a recall involving some check valve malfunctioning, overfilling a fuel tank such that fuel goes past the gas cap. Could the slime be dried fuel and I have this problem? I've only seen the slime once.

On Sun, 12 Oct 2003 08:54:07 -0700, Brent Olson rearranged some electrons to form:

Maybe, but there is something else going on to make that pump run so long. Maybe the relay is sticking? You might want to put a fuel pressure gauge on the fuel rail and see what pressure you're getting...IIRC it should be about 40-50 psi. I would also check the pressure regulator.

Seems like I read something about that...my old truck (89) with dual tanks never had a problem like that, though.

I am having something of the same problem: almost ran out of gas one night so ifilled up my other tank and switched over to it, almost immediately the truck started running very badly. got it home and cut it off then it would not crank again. It would turn over but never fire and run. both fuel pumps work replaced the filter got pressure at the fuel rail. I have been told I may have clogged injectors. if this is the case how do I check them? and if this isnt the problem what might i check next? Any help would be appreciated. thanks Mick

IIRC, the problem is with the return, pulls out of one tank, returns to the other one. Not a problem if it's empty, but can overfill if there's not enough capacity.

Check these links for some numbers:

David Jones djonesLSidaho.com

=3D=3D =3D=3D check yer fuel pressure regulator

pinch off the return hose....on the tank side of the regulator when it acts up again.

see what happens

marshmonster

. .

1990 F150 fuel delivery problem Group: alt.trucks.ford Date: Sat, Oct 11, 2003, 10:14am (CDT-2) From: snipped-for-privacy@bitrealm.com (Brent=A0Olson) The truck cranks fine, so I got out the meter. With the key on but not started, I began checking for ignition voltage, all the while the fuel pump is running. I have a dual tank longbed f150 with the 6-cylinder and 5spd manual transmission. The fuel pump runs when either on the front or rear tank, but obiously switches to the other pump when I change tanks. I tried to start it a few times after unplugging/plugging various wires to no avail. After about 5 minutes and reading the manual, I hear the fuel pump finally turn off. I jump in the truck and it starts right up. If I turn it off now, then back to the on position, the pump runs for less than a second, and turns off, like its supposed to do in the first place and will start right away.

Question: what could cause this? It can't be BOTH fuel pumps, can it?

What would you think will happen? Maybe ruin his fuel pump by running the pressure so high? Bob

. . .

(original post...start of thread)

1990 F150 fuel delivery problem Group: alt.trucks.ford Date: Sat, Oct 11, 2003, 10:14am (CDT-2) From: snipped-for-privacy@bitrealm.com (Brent=A0Olson)

The truck cranks fine, so I got out the meter. With the key on but not started, I began checking for ignition voltage, all the while the fuel pump is running. I have a dual tank longbed f150 with the 6-cylinder and

5spd manual transmission. The fuel pump runs when either on the front or rear tank, but obiously switches to the other pump when I change tanks. I tried to start it a few times after unplugging/plugging various wires to no avail. After about 5 minutes and reading the manual, I hear the fuel pump finally turn off. I jump in the truck and it starts right up. If I turn it off now, then back to the on position, the pump runs for less than a second, and turns off, like its supposed to do in the first place and will start right away.

Question: what could cause this? It can't be BOTH fuel pumps, can it? Re: 1990 F150 fuel delivery problem...pressure regulator... =3D=3D =3D=3D Marsh Monster seemed to be concerned enough to answer the cry for help after reading all the weird diagnosis proceedures given..... to put forth this........

check yer fuel pressure regulator pinch off the return hose....on the tank side of the regulator when it acts up again. see what happens

marshmonster ..................................................................... ................................................................... During a recent episode of alt.trucks.ford we here snipped-for-privacy@nospam.com (Bob) flub his lines and improvise with......

What would you think will happen? Maybe ruin his fuel pump by running the pressure so high? =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0 =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0 =A0Bob ..................................................................... ..................................................................... which prompted ole Nubbs to quit stirring the pot of shroom juice that was simmering..... long enough to enlighten BOB with this......................

B.O.B. what do YOU think would happen?

Not very familiar with fuel systems are you there BOB ???????

BOB.......yer homework assignment is...... To write a 3 paragraph post that outlines in detail, the operation of an injector fuel system. Somewhere in those 3 paragraphs.......see if you can't explain why the fuel pump only runs for a few seconds when the ignition key is cycled to the "Run" postition.

yes BOB.....you may use GOOGLE as a research tool......just be sure to give credit for the resource material.....and be sure to give Marsh Monster credit for initiating the research papers topic for you.......

TO BRENT...... pinch off the return hose to see if the symptomj changes.

Nubbs McFarkle ~thinks BOB should have at least contributed to the thread with a diagnostic proceedure for the symptom~ . . .

(original post...start of thread)

1990 F150 fuel delivery problem

Group: alt.trucks.ford Date: Sat, Oct 11, 2003, 10:14am (CDT-2) From: snipped-for-privacy@bitrealm.com (Brent Olson)

The truck cranks fine, so I got out the meter. With the key on but not started, I began checking for ignition voltage, all the while the fuel pump is running. I have a dual tank longbed f150 with the 6-cylinder and

5spd manual transmission. The fuel pump runs when either on the front or rear tank, but obiously switches to the other pump when I change tanks. I tried to start it a few times after unplugging/plugging various wires to no avail. After about 5 minutes and reading the manual, I hear the fuel pump finally turn off. I jump in the truck and it starts right up. If I turn it off now, then back to the on position, the pump runs for less than a second, and turns off, like its supposed to do in the first place and will start right away.

Question: what could cause this? It can't be BOTH fuel pumps, can it?

Re: 1990 F150 fuel delivery problem...pressure regulator...

== == Marsh Monster seemed to be concerned enough to answer the cry for help after reading all the weird diagnosis proceedures given..... to put forth this........

check yer fuel pressure regulator pinch off the return hose....on the tank side of the regulator when it acts up again. see what happens

marshmonster ..................................................................... ................................................................... During a recent episode of alt.trucks.ford we here snipped-for-privacy@nospam.com (Bob) flub his lines and improvise with......

What would you think will happen? Maybe ruin his fuel pump by running the pressure so high?

Bob ..................................................................... ..................................................................... which prompted ole Nubbs to quit stirring the pot of shroom juice that was simmering..... long enough to enlighten BOB with this......................

B.O.B. what do YOU think would happen?

Not very familiar with fuel systems are you there BOB ???????

BOB.......yer homework assignment is......

To write a 3 paragraph post that outlines in detail, the operation of an injector fuel system. Somewhere in those 3 paragraphs.......see if you can't explain why the fuel pump only runs for a few seconds when the ignition key is cycled to the "Run" postition.

yes BOB.....you may use GOOGLE as a research tool......just be sure to give credit for the resource material.....and be sure to give Marsh Monster credit for initiating the research papers topic for you.......

TO BRENT...... pinch off the return hose to see if the symptomj changes.

Nubbs McFarkle ~thinks BOB should have at least contributed to the thread with a diagnostic proceedure for the symptom~ . . Okay marshy (no your sock puppet didn't fool anyone.) The reason that the pump only runs for a couple of seconds when the key is turned on is because that's how long the PCM is programmed to turn it on if it doesn't see a signal from the PIP sensor. It doesn't know or care what the fuel system pressure is. That's why when you deadhead the system aka pinch the return hose off, the fuel pressure at the pump can and will go as high as 120PSI. If you haven/t already figured it out that is very hard on the pump... worse even then running them out of fuel. That's also a very good reason for people to change fuel filters regularly, a plugged filter will also cause the pressure at the pump to skyrocket.

Bob thinks Marshys silence is deafening..... could it be that Marshy has been smoking to many shrooms and really doesn't know shit about Fords EFI systems? Bob

. . (original post...start of thread)

1990 F150 fuel delivery problem Group: alt.trucks.ford Date: Sat, Oct 11, 2003, 10:14am (CDT-2) From: snipped-for-privacy@bitrealm.com (Brent Olson)

The truck cranks fine, so I got out the meter. With the key on but not started, I began checking for ignition voltage, all the while the fuel pump is running. The fuel pump runs when either on the front or rear tank, but obiously switches to the other pump when I change tanks. I tried to start it a few times after unplugging/plugging various wires to no avail. After about 5 minutes and reading the manual, I hear the fuel pump finally turn off. I jump in the truck and it starts right up. If I turn it off now, then back to the on position, the pump runs for less than a second, and turns off, like its supposed to do in the first place and will start right away.

Question: what could cause this? It can't be BOTH fuel pumps, can it? =3D=3D =3D=3D Marsh Monster seemed to be concerned enough to answer the cry for help after reading all the weird diagnosis proceedures given..... to put forth this........ check yer fuel pressure regulator pinch off the return hose....on the tank side of the regulator when it acts up again. see what happens

marshmonster ............................................. ............................................. =A0=A0During a recent episode of alt.trucks.ford we here snipped-for-privacy@nospam.com (Bob) flub his lines and improvise with......

What would you think will happen? Maybe ruin his fuel pump by running the pressure so high?

Bob ............................................. ............................................. which prompted ole Nubbs to quit stirring the pot of shroom juice that was simmering..... long enough to enlighten BOB with this......................

BOB.......yer homework assignment is......

=A0=A0=A0=A0=A0=A0=A0=A0To write a 3 paragraph post that outlines in detail, the operation of an injector fuel system. Somewhere in those 3 paragraphs.......see if you can't explain why the fuel pump only runs for a few seconds when the ignition key is cycled to the "Run" postition. yes BOB.....you may use GOOGLE as a research tool......just be sure to give credit for the resource material.....and be sure to give Marsh Monster credit for initiating the research papers topic for you.......

TO BRENT...... pinch off the return hose to see if the symptomj changes.

Nubbs McFarkle ~thinks BOB should have at least contributed to the thread with a diagnostic proceedure for the symptom~ .

Okay marshy (no your sock puppet didn't fool anyone.) The reason that the pump only runs for a couple of seconds when the key is turned on is because that's how long the PCM is programmed to turn it on if it doesn't see a signal from the PIP sensor. It doesn't know or care what the fuel system pressure is. That's why when you deadhead the system aka pinch the return hose off, the fuel pressure at the pump can and will go as high as 120PSI. If you haven/t already figured it out that is very hard on the pump... worse even then running them out of fuel. That's also a very good reason for people to change fuel filters regularly, a plugged filter will also cause the pressure at the pump to skyrocket.

Bob ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Bob thinks Marshys silence is deafening..... could it be that Marshy has been smoking to many shrooms and really doesn't know shit about Fords EFI systems? =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0Bob ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Bob, Marsh says he apologizes......and appreciates that you didn't flame him a new one....but instead jest listed facts. But to his credit.....you've got to admit.... pinching off the return line would be the quick way to check it. No one told the dude to leave it like that.....just to see what would happen.

one last thing......... Nubbs would like you to know...... that shrooms are not meant to be smoked.....

Scrib Abell ~peaks down into the simmering pot that ole Nubbs is stirring.......mmmmmmm....looks like a good batch of tea...~ . . . .

this message will self-destruct.......

after the first glass of shroom juice...

message

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with......

running

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Yeah dude, I think Mushy's been siphoning too much gas lately and it has caused *more* brain damage than he was born with.

I crawled underneath to have a look. It APPEARS as though the fuel lines go along the frame rail, then split and go to both tanks. I don't see three fuel pumps, but who know for sure.

I don't have a fuel guage (yet), but here's some further diagnostics. If I depress the tire-valve on the fuel rail, nothing comes out. If I turn the key on for about 10 seconds (fuel pump running) then turn the key off, I get about a spits-worth of fuel out of the valve. If I leave the key on with the pump running then depress the valve on the fuel rail, fuel comes shooting in a constant stream. The valve is horizontal and I would guess the fuel is shooting about 4 feet. The truck will NOT start until the fuel pump shuts off.

I took the vacuum hose off the fuel pressure regulator, no fuel coming out here.

It seems the system won't pressurize, and seems to run fine once started. Can someone explain how the fuel pressure regulator in this vehicle works? As there appears to be no sensors, and only engine vacuum to control the valve, it would seem as if it's designed to be closed when the engine is off so that fuel pressure can build; but once the engine is started, it opens and lets fuel back to the tank, not really regulating at all. Does the fuel pump shut off once pressure is established, by detecting back pressure?

On Mon, 20 Oct 2003 10:40:59 -0700, Brent Olson rearranged some electrons to form:

There's one inside each tank, plus the high pressure pump on the frame rail.

I don't think so, it's just supposed to run for a few seconds and stop. The fuel pressure regulator is designed to keep a constant pressure drop across the injectors. I'm still thinking that's possibly your problem. Maybe someone else has an opinion?

check the presure regulator like I told you to a week ago.....

then replace the fuel pump if the test didn't give you any results.

scrib abell ~:~believes brent is using selective response diagnostics.....~:~

You mentioned I somehow pinch the return line and see if that stops it. There doesn't seem to be enough room to kink the line, and is that a good idea?

I have now replaced the fuel pressure regulator. In following the fuel lines, I do not see a fuel pump on the frame rail (drivers side). The lines appear to go straight from the engine bay to the top of the fuel tanks.

After replacing the regulator, I have the same behaviour. I can hear the fuel pump running, and running, etc. Once it stops, about 4 minutes, the truck will start. If I switch tanks, the other fuel pump runs and runs and also eventually stops and I can start the truck. Does this truck have three fuel pumps? I called the dealer inquiring about getting a high pressure pump, and he indicated there are only two pumps, one in each tank. They can't both fail at the same time, can they?

Does the fuel pump shut off once pressure is established? What could the matter be?

Dr. Watson? I'll send $10 to anyone who can figure this out without me having to go to a dealer. So far I've bought a regulator I didn't need for $40. What a pain to install, by the way.

No, kinking the line isn't a good idea and it won't prove anything.

Well, I suppose they could but the odds are about the same as me winning the lottery tonight.

The pump shutting off has nothing to due with pressure. When the key is turned to the run position the ECM grounds the fuel pump relay for about two seconds and then if it doesn't see a signal from the distributor it ungrounds the relay shutting off the pump.

I don't think you have a typical pattern failure, it's more of an oddball type of thing. What you need to do is find a good tech, not necessarily a dealer but someone very familiar with Fords and have it checked out. Sounds to me like a PCM problem. It could be the PCM itself, but the Ford ones rarely go bad. Also could be a bad power or ground wire to the PCM, or even something causing a false signal on the ignition pickup circuit. Has anyone rewired anything under the hood? If you have other information you should post it..... It can only help. When it won't start does it have spark? Have you tried a noid light on the injectors... is the PCM firing them? Bob