fuel pump won't shut off

I have a 91 f-150 4.9L. A couple of weeks ago it started cutting out, could'nt step on the gas, seemed like it was flooding. when I cut it off , it would'nt crank back . it would turn over but not crank. Had it hauled to a local garage, where he kept it for a week. Changed plugs,wires, distributor,dis.cap,rotor. module. He finally got it cranked. Did good for about 5 days, then done the same thing. Now when I turned the switch, if the fuel pump comes on for 2 seconds then shuts off, it will crank. But if the fuel pump stays running, or chattering, it won't crank. What is suppose to cut the fuel pump off?

there should be a fuel pressure Switch that controls the pump. But i think most of them a pat of the pump so my guess is you need a new pump.

They have a fuel pump relay and a eec relay that supplies power to the fuel pump relay. On your F-150 they should have a pack of relays close to the drivers side fender. Check these out before buying a new pump.

Guess what, my 90 does the same thing. No one on AF has come up with a solution so here comes great news. Its the computer. Want to test the theory? Unhook your battery and then try to start. Or spray ether into the intake before rocking the key. Either way you will go mental trying to track wires and relays. 88-91 F150s have this problem. I've owned and burned 3. Good luck.

You are supposed to have a fuel pressure regulator which controls pressure. The excess is sent back to the tank. Check the vacuum hose to the pressure regulator if it has gas in it replace the regulator. Check the pressure with a gage. Normally you don't have a bad computer.

i had same problem it was fuilpump relay shortingout try banging itfornow but should change it theres two square relays one black one brown you change blackone

"when I cut it off , it would'nt crank back . it would turn over but not crank"

I think the above is almost unintelligible.

For greater understanding, it is important that we comprehend "terms of art".

An engine that is turning over is cranking. An engine that is cranking is turning over but is not yet started. You cannot have an engine that is turning but not cranking, unless it is running and therefore turning over while it runs.

I repeat that an engine turning over is called cranking because that is how you used to start an engine, by turning a crank or "cranking" it.

what he means in the starter is turning the engine over, but it doesn't actually start.

you knew what he meant, don't be rude.

Regards,
AF Moderating Staff. :smooch:

MY 1990 f150 is doing the same thing. The pumps run continuosly when the ignition switch is in the on position. I have taken it to my own maechanic and the ford dearlership after he was unable to diagnos the problem. I have replaced the distributor module, and the ecm relay. I have checked the pressure regulator and it is fine. The only thing left to relace that I can think of is the fuel pump relay or the ecc itself. I don't believe it is the fuel pump relay (and please correct me if I am wrong) becuse the pumps are running. I am in the midst of tracking down a replacement ecc at a reasonable cost. Any help or insight would be greatly appreciated.

Seems like if your key was on and the fuel pump kept running either you have a normally open fuel pump relay that is closed(ie contacts welded) or something is sending it power keeping it closed(ECM) and possibly your fuel pressure switch is keeping that circuit closed as well, which should open once it comes upto pressure.

I replaced the fuel pump relay today. The pumps run for 1-2 seconds and shut off as they are supposed to. The engine starts and is running like a champ. I am not completed convincved that I have solved the problem though as this has been intermittent to say the least. Time will tell. I do believe this eleminates the fuel pressure regulator as a source of the problem though (please correct me if I am wrong). Could something be causing the fuel pump relay to foul? Does an eec just go out when it goes or could it work intermittenly causing my confusion? Any help or insight is greatly appreciated.

I replaced the fuel pump relay today. The pumps run for 1-2 seconds and shut off as they are supposed to. The engine starts and is running like a champ. I am not completed convincved that I have solved the problem though as this has been intermittent to say the least. Time will tell. I do believe this eleminates the fuel pressure regulator as a source of the problem though (please correct me if I am wrong). Could something be causing the fuel pump relay to foul? Does an eec just go out when it goes or could it work intermittenly causing my confusion? Any help or insight is greatly appreciated.

:banghead:
I went to start my truck today after work and the problem has presented itself again. The pumps run continuously. The relay seems to have fouled again or the eec is not sending the proper signal to the the relay. Any advice woulfd be much appreciated.

A relay,is nothing more than an electrically operated,as opposed to a manually operated switch. Something is either activating the relay at the wrong time, or it has malfunctioned.If the replacement relay has,in fact failed,it would seem to indicate excessive current through the relay.

Or your Pump never pressures up enough to drop out a pressure switch keeping the relay made...

Dear moderating staff,

There is nothing in the least rude about my post. It is a clarification of the terms of art we all use and know, which will assist this community in diagnosing the difficulties described herein.

To characterize this statement "when I cut it off , it would'nt crank back" as "almost unintelligible" is a plain statement of fact. Nothing insulting is contained in my words. Possibly you can state what was meant (can you?), but that does not make my characterization any less accurate.

It's hard enough to diagnose problems over the phone or internet when we all speak the same language.

If someone called you on the phone and said "My engine won't turn over." What does that mean to you? Wouldn't it be best if it meant the same to the caller and anyone else who might get involved?

It is your behavior that is rude. You censure me for providing insight into the special cant of mechanics. It seems plain that you believe that most readers/posters are not intelligent enough to learn how to describe their problems using proper terminology. I disagree; I believe they are.

"You know the thing - the thing that goes 'round..." Ask the moderators.

:banghead:
I went to start my truck today after work and the problem has presented itself again. The pumps run continuously. The relay seems to have fouled again or the eec is not sending the proper signal to the the relay. Any advice woulfd be much appreciated.


:grinyes: I replaced the eec with a refurbished one from the auto stoire and we seem to be in business. The truckj has ran for fine for the last three days. I appreciate everyones help.

my advise to you to replace your eec. it is located under the driver side kick panel. it purtrudes through the firewall to a wire harness. i am in know way an auto mechanic, i learned this the hard way.