HELP!!! fuel pumps runs

[predator]

ok first im going to start with what i bought a year ago...it is a '91 explorer with a 4.0 and a 5 spd. the tranny has 12,000 miles on and the motor has 30k. the motor is out of a '96 ford explorer, the guy i bought it from told me that he just bolted on the '91 upper motor parts to get the wiring right. but after he did that the fuel pump would run when the vehicle is turned off so he told me just to lift the fuel pump fuse out and it would stop, so i did this until the vehicle started to run like crap and then it wouldn't start. so me and a good friend of mine spent 6 days with a meter and we tested every connection in the vehicle and after we ran a wire from the ground on the maf sensor it started and got back to normal.


fast forward 10 months- i painted the explorer and put in a new maf sensor and new battery cables. after i was driving it around for a couple hours i shut it down and the fuel pump started running again!!! except this time it seemed intermittant, not all the time but just every now and then, so i checked the ground and on the end that we bolted to the body i cleaned with a wire brush and reattached. i have not gotten a chance to replace the other end of the ground but i did check it but it seems ok, but im replacing it anyways..

my question-why does the fuel pump run when the vehicle is turned off? is it because the maf is not grounded? is there any thing else that could be causing this? any else ever have any problems like this??

thanks for your help!!

 

[RobbieD]

I don't think the MAF is causing this; it sounds like plain old wiring problems. The fuel pump relay doesn't even get power to its coil until the key is turned on, and EEC relay energizes. Then the EEC has to send a ground to the other side of fuel pump relay coil to energize it, which switches power to the fuel pump to make it run. So, if the pump is getting power when the key is off, there's snakes in the wiring somewhere- likely put there by the previous owner.

The best advice I can give you is get yourself the Ford EVTM (Electrical and Vacuum Troubleshooting Manual) for your truck, so that you have something showing how the wiring should be, and then start going through the wiring. It really sounds like you have some rigged wiring still in the truck from before you got it.

 

[Southern3.0]

The contacts in the Pump relay could be intermittently sticking, and that would have nothing to do w/ the ECC relay. So Id say Replace the fuel pump relay.

But My old '91 Ranger did the same exact thing and 3 different pump relays didnt fix it, I could never figure it out so I ended up just putting a relay In the pump circuit that was triggered off the radio. Wish I still had the truck cus that was somthing I always wanted to know what was wrong with.