92 mustang 5.0 Problems

themyst09 said:

I have a mind bogling problem with a 92 5.0 mustang. when you turn the key on the fuel pump is suppost to turn on, run for a few seconds than shut off. the one ive been working on will not shut off. i have installed a brand new gas tank, fuel pump, fuel filter, injectors, fuel regulator, and relays. occassionally after sitting the car will run. when you turn the key and the pump shuts off the car runs awesome and has no problems. no body can figure out what the problem is with this car i need some help any ideas?

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if i am not mistaken the only power source to the fuel pump is the fuel pump relay which is located under the drivers seat...maybe its faulty and it sticks? just a thought...

jim

Well The pump turns on to prime the fuel system. It stops when the pressure builds enought to start the car. I am not sure what turns it off but it may have something to do with the pressure or the computer. I would assume that when pressure builds it stops the pump from pumping unitl the engine starts then it runs until the engine is off.

Remove the release valve (schrader) sp?. and install a guage and see if you have any pressure. Maybe the pump is not getting enough fuel to build pressure or you have the line inside the tank, where the pump hooks to the pickup is bad and allowing fuel to spill in to the tank instead of heading up the pickup.

BTW those little lines inside the tank for the most part are pressed on but will pop off. Also if the pickup has a crack somewhere before it gets to the outside of the tank it will not feed the fuel system and the pump will run on.

As said, the pump primes for about 5 seconds. The EEC has no idea what the rail pressure is (deadhead fuel systems do, but not ours). The prime-out is purely a function of time. The EEC is what controls this - the ground on the control side of the FP relay comes from the EEC. This same wire is able to be grounded at the self-test connector. If this occurs, the pump runs anytime the key is on.