1991 f-150 5.8
on my last post i was told to ground the wire at the test plug to see if the chattering of the relay would stop. i did this and the relay stopped chattering. is this a permanent fix. do i leave it grounded or do i have to look for a ground at the EEC. if so where is the computer located or does someone have a diagram that would help me out. thanks. john

 

No you do not leave pin#6 of the test connector grounded. When you ground it you bypass the EEC and it can not turn off the fuel pump if the engine dies.

 

Here is a diagram of your system:

http://www.autozone.com/images/cds/g...3d800a3a4e.gif

 

thanks a lot subford for your input and the diagram. from the looks of it power to the fuel pump relay comes from the EEC power relay. i will replace the power relay just in case that it is causing the problem of the chatter. thanks again. john

 

Chattering is normally caused by either low voltage or bad connections. If grounding pin #6 stopped the chatter then maybe pin #22 at EEC connector is not OK or the wiring to it.

 

One other though is to make sure that the small wire (black with a white stripe) coming off the Neg Post of the Battery has a good connection as this is the ground that the EEC uses to ground the Fuel Pump Relay.

 

i will have to wait to try your suggestions tomorrow as it is raining today. hopefully this will work. i'll post as soon as i get a chance to check them out. thanks, john

 

i tried restarting the motor and when i turned on the ignition the fuel pump ran constantly and the motor would not start. i grounded the fuel pump relay and the chattering was still there. i ran a code check and a code 15 came up on the scanner which is related to the computer memory. after running the scanner the moter would start for about 8 times then it would go back to the chattering and no start also the tad and tab relays were also chattering. i guess that the computer is at fault. if you think that that the grounds 40 and 60 are in question let me know. i think that the computer is under the radio mid dash area. i was told that it was located on the left kick panel but all of the wires lead to the mid councel area. any help will be appreciated. thanks again. john

 

Yes it sounds like the computer (PCM) and it would be located in the left kick panel and accessible from under the hood with the inter fender loosened.

 

thanks, i will try and access the pcm hopefully within the next couple of days and will post.