Fuel pump problems

[BK_CAULEY]

symptoms: turn key forward pump comes on and wot shut off. cycle 2-3 times and on the 3-4 cycle pump wont come on. let it sit for 5-10 minutes it comes back on.

tests so far: new fuel pump relay. new fuel pump. and the pink and whatever striped color wire coming out of the solenoid has 12v the entire time. even when pump isnt running.

im thinking its grounding out somewhere. i dont know. i just know its extremely frustrating.

 

[stykthyn]

what year/model? Almost sounds like a ccrm issue, but that would only work on SN and 4 banger cars....

 

[liljoe07]

The Computer controls the Fuel Pump relay ground. Thats what activates the relay to engage the pump. So, if the relay ground was grounding out side of the computer, you can unplug the computer and turn the key on. If pump still comes on, then the relay ground is grounded else where in the circuit.

Pump doesnt come on, its in the computer. And you may want to open the computer up and check the condition of the 3 blue electrolytic capacitors inside. If they are leaking acid onto the board then it can cause the same issues as you are getting.

 

[BK_CAULEY]

its a 1993 gt 5.0.

so the ground cuts the power. the same way the injectors do? is there any way i can cut the ground wire in the harness and apply a ground to the fuel pump ground wire from another source manually then remove it to see if it cuts on and off as supposed to?

 

[liljoe07]

Yes, the computer supplies power only to a few of the sensors. Everything else is controlled by a ground. I dnot reccomend you cut any wires. But if you plan on soldering it back, then its no biggie.

It would be better if you unhooked the relay and computer and used a meter and test the relay ground to a body ground. Use the ohms or continuity setting. Open line should show in the meter.

 

[BK_CAULEY]

new problem.

went out turned the key pump came on had 40psi turn it over to start it up while i had pressure and got nothing. wont run. and i could here the pump running and had the good pressure at the schrader valve.

keep in mind, the car was running perfect when parked. sat for a week or two and went out to start it and all off this went down.

 

[liljoe07]

You need to check the computer inside. The Capacitors inside can cause this exact same issue.

That being said, run the Engine Off codes from the computer. And post them up. Some times that can lead you in a good direction.