[roadrash88]

Having problems with fuel pump. After about 10 minutes idling the fuel pump starts kicking on and off. I have changed the fuel pump, fuel filter, fuel tank, spark plugs, blown air through the fuel lines and is still acting up. Please any suggestions.

 

[Frango100]

Fuel pump relay?

 

[roadrash88]

I tried swapping relays out didn't make a difference but I'm gonna buy a new one tomorrow

 

[Frango100]

If you already swapped it with an other known good relay then its no use to buy an other one.
Did you measure the voltage to the fuel pump and did it go to 0 V?
The fuel pump relay is switched by the PCM. You could check the fuel pump wiring by disconnecting connector C3 from the PCM and connect pin 19 from the wire bundle connector to ground. The fuel pump should run continuosly. If it still goes on/off, then there is some electrical problem in wiring. If it doesn't, most probably the PCM is the culprit. I'm not sure for how long you could let the pump run like this without fuel usage by the engine, but i would imagine that the fuel pressure regulator will return the fuel to the tank.

 

[roadrash88]

Where is the PCM located

 

[Frango100]

Under the hood, against the bulkhead close to the right fender. Its just behind the coolant overflow reservoir. It has 3 connectors with a lot of wires to it.

 

[roadrash88]

I can't figure how to check by grounding pin 19. But while idling when it starts kicking on and off it stays on for 3 seconds shuts off for 15 and just keeps repeating.

 

[roadrash88]

And while driving the sentry key indicator light came on but went off after I killed and cranked it

 

[Frango100]

With ignition switch in run and grounding pin 19 from connector C3 from the PCM will activate the fuel pump relay and this will send power to the fuel pump. If the pump runs ok like this, the problem is most probably in the PCM.
How did you determine that the fuel pump is on for 3 seconds and off for 15, did you measure the voltage?
When you switch the ignition in on but don´t start, the PCM will switch on the fuel pump for 3 seconds and then switch off if it doesn´t get a speed signal from the engine.
Did you already check for any fault codes set by the PCM? Ignition switch off/on three times and leave in on at the third time. The odometer will show DONE or any fault code(s).

 

[roadrash88]

I could feel the pump running through the fuel lines at the fuel filter an I timed it

 

[roadrash88]

And it's not throwing any fault codes or at least not kicking on the check engine light

 

[Frango100]

You can have a code set without the check engine light on, so if you didn´t do the keydance yet, give it a try.
Did you feel the pump running with the engine off? I don´t believe that the engine will stay running when the fuel pump is off for 15 secs.

 

[roadrash88]

It's not showing any codes with keys acne either

 

[roadrash88]

Ya the pump runs with the engine off like it supposed to

 

[Frango100]

Ya the pump runs with the engine off like it supposed to

??? When you put the ignition switch in run but doesn´t start the engine, the fuel pump should run for 3 seconds and shut off, its not suppost to keep running or run again after some time when the engine is still off. if this happens, i would say that the PCM is faulty.

 

[roadrash88]

It runs for three seconds with the key on and engine off

 

[Frango100]

And with the engine on it runs 3 secs and stops for 15 secs and the engine doesn't shut down?

 

[roadrash88]

It try's to but right before it shuts down it kicks back on

 

[Frango100]

My suspect is still the PCM, thats the one who makes the ground for the fuel pump relay.

 

[roadrash88]

Changed the PCM still doing the same thing. Do you happen to know what the best fuel pump is to put in it