I am having fuel problems. I replaced the fuel pump relay and everything seemed good. I think it is the fuel pump. Sometimes it will hum when you try to start the truck up. If you do not hear it the truck does not start. If you hear it the truck will start. Is the pump the best place to start. Just replace it or does this sound like a different part. 2000 f150 4.6 Just under 90,000 miles. As always thanks for any help.

 

Does it sound scratchy when you here it before it starts, or does it vibrate sort of ?

 

It sounds pretty much normal. You here it hum,but to me thats all. You either hear or you do not. If you turn the key back and forth on acc. It will usually startafter a couple times.

 

Sounds like a short , I would replace the relay first- that could be going bad..

Check out your wiring , look for something corroded, those wires by the inertia switch in the cab like to corrode..

 

Thanks jbrew. I will spend sometime looking at the wires before replacing the pump. I rerplaced the relay but maybe it went bad again. I will replace it also. I think it was 12 bucks.

 

Also look at your receptacle - were the relay plugs in , sometimes this corrode as well . Last resort, your pump wires can work loose, check this out if nothing else seams to help.. Those Pumps are expensive, I 've had to fix mine before..

 

There is a fuse, a relay, an inertia switch.
It may not be the fuel pump.
Sub the relay first.
If the relay fails, the PCM as well as the pump fails.

 

How do you check to see if the relay is bad. Occasionally my truck will not have fuel pressure when attempting to start it. Thank you.

 

One way is to swap relay locations with another relay.
If a problem follows the relay, some other function may not work.

 

I would go the relay route first. Dirty or burnt contacts are common

 

do i need to disconnect the battery before i remove the relay?

 

No. not at all. just pull the one for the fuel pump and change it with the one for maybe the horn or a/c to check it out

 

Thank you...I will try that and see if it works.

 

On the new and old I put a meter on it. I got 65 ohms on the outside pins on the old one. On the new one I got 72 ohms across the same pins. Does anyone know how many volts you should have at the interia switch. I thought 12 but I get 6.