When i got the truck it had a switch wired up to run the fuel pump (inline hi-pressure). I swapped out the fuel pump relay with a new one, and when i did, it started working how it was supposed to. I would turn the key and it would run for about 1-2 seconds to prime the system, then when it started the pump would run the whole time.

well, i was driving down the road the other day and it all the sudden died. I noticed that the fuel pump wasnt kickin on, so i hardwired it, and cranked it up and drove it home. What can i do to check the electronics that make the fuel pump relay activate? How can i make it all work? I have a switch wired back in right now and its working fine, but i would like to get it back working again. I have checked all the wires as far back as i could trace, all the way from the pcm to the relay, and everything that i can think of. If i pull the cover off of the relay and pick it by hand, the fuel pump kicks on, and i have swapped/tested the relay numerous times and it is fine. Any ideas what to check? The eec relay and fuel pump relay have been replaced somehow with new relay bases from what i can see and im not even sure if the wires going into each relay are hooked up where they are supposed to, can anybody give me the wiring diagram for those two relays? like what color wires should go to coil/constant power/etc.... the chiltons manual and the haynes manual show them but they are crappy diagrams, dont show what stuff goes where on the relay, just the wires that go into it. Thanks for any input!

 

All I have is the Haynes also, but if you have the covers off the relays, then you should be able to figure out and translate the diagram to the relay pins.

On the fuel pump relay, the yellow wire is power in from a fusible link, and should go to one of the relay contacts. Pink/black is power out to the inertia switch, and should go to one of the other contacts in the relay.

Red is EEC power and should go to one side of the relay coil. The tan/lightgreen is the negative of the coil of the relay, so it hooks to the other side of the coil, and it goes to the computer. The computer grounds the relay to activate it, activating it for a period of time during starting like you mentioned, and then holding the relay in once it verifies signals from the distributor(this tells the computer the engine is running).

 

All I have is the Haynes also, but if you have the covers off the relays, then you should be able to figure out and translate the diagram to the relay pins.

On the fuel pump relay, the yellow wire is power in from a fusible link, and should go to one of the relay contacts. Pink/black is power out to the inertia switch, and should go to one of the other contacts in the relay.

Red is EEC power and should go to one side of the relay coil. The tan/lightgreen is the negative of the coil of the relay, so it hooks to the other side of the coil, and it goes to the computer. The computer grounds the relay to activate it, activating it for a period of time during starting like you mentioned, and then holding the relay in once it verifies signals from the distributor(this tells the computer the engine is running).

 

Most of the time this is caused by poor connections on the bottom of the relay socket.
You can ground pin #6 of the EEC Self-Test connector with the key on to operate the fuel pump relay.

Here is a diagram of the fuel system:


And one of the Test Connector.


/

 

I checked the codes, and got a code 87, which is fuel pump circuit failure primary. I have checked all the wires i can, and if i manually pick the relay or test from the self test plug, it turns on the fuel pump. What should i look at now? im lost

 

Check the small black wire with a green stripe coming off the NEG (-) post of the Battery.
Sounds like it may have lost ground to the post.

The 87 means the Fuel Pump Relay did not close when told to do so by the computer.
You may also have a bad pin for the relay in the computer plug.

Note that you can also set this code by grounding pin #6 of the EEC self-test connector.

This could mean that you have a bad Computer also if the pumps run by grounding pin #6 and they do not run for one second when you turn on the key. But make sure the computer has a good ground and power at the pins on its plug before condemning it.

 

What exactly do I check for the ground to the pcm? Can I just add an additional ground to the computer? Do I just hook it to the casing?

 

As in the diagram above pins #40 & #60 are the ground pins at the computer plug and are grounded through the small black wire with a green stripe coming off the NEG (-) post of the Battery.

 

I'm having same exact issue new ,I maybe out of proper order may one of you'll please wouldn't mind helping anfool out

 

Start a new thread. Tell us what year/model/engine and other info on your truck, and explain your problem to us.

Go here https://www.ford-trucks.com/forums/forum62/ and look in the upper left corner were it says "new thread". Give it a title that alerts us to your problem in a few words.

 

I had the same problem. Found a broken wire going to fuel pump from the relay