I have a 1991 Ford F-150 4.9 6cyl. auto. It is a daily driver. Last friday, I got off work, started my truck, was looking through some papers and then the truck died. It was probably running no more than a minute and a half. It hasn't started since. A few people I've talked to suggested either the fuel pump, the fuel filter, or the fuel pump relay. I replaced the fuel filter and no change. The truck has two tank each with their own fuel pump. When i switch tanks, nothing changes, so I don't think its a fuel pump. I bought a fuel pump relay, but can't find where it goes. I bought the truck used and do not have a owner's manuel. Can someone tell me where to locate the fuel pump relay OR give me another suggestion about what could be wrong with my ford pick up? Please post. Thanks, Greg.

 

I have an 88 and on mine its right on the air cleaner box drivers side,my relay for fuel is green color,might be the same as yours.

I am not shure on this but if you have the right relay it should just fix the fuel one not the others, pin diffrence,mine is 4 pin the other relay is 5 pin.

CrimeScene

 

The relay I bought is a 5 pin. It looks life kinda like a night light w/ no bulb. I can't find anything that looks like it. The color of the replacement is gray.

 

Could be a fuel pump relay...but since it won't start it could be electrical. Do you hear the fuel pump(s) cut on for a couple of seconds when you switch the key to "on" (not start, but just "on")? If not, then it certainly could be a fuel pump replay.
I recommend a good quality relay from a ford dealership, I have had bad relays from cheaper auto parts stores and the hassle it causes isn't worth the savings.

 

Check the inertia switch, it may need to be reset.

 

Well me and you are in the same boat with the same problom,today I am going to get new relays,two of them for mine and see if mine will start.

Unless your truck is a vic of some back yard farm boy fixing it should be there on the air cleaner box right by the crank case breather tube,there kinda under a cover about 6in long,be careful pulling them down so you do not yank any wires out.

CrimeScene

 

Hey guys, new to this forum but this is exactly what I have going on with my stepson's 1990 F-150. We changed the relay and the fuel pump with no luck. He had the truck warming up one morning before school and it died on him. The Inertia was not tripped so we are good there. My problem seems to be less than 7 volts getting to the fuel pump. I do have 12 volts to the relay. Maybe GREGZESSIN is the same problem. Does anyone have any idea?

 

Sounds like you are using a voltmeter, they are very misleading, the 7 volts is more than likely 0 volts, use a test light that loads the circuit so you know what you have.
As said above does the fuel pumps come on for one second when you turn on your key and then stop?
If not does the Power relay click when you turn the key to on?

 

The relay does click. There is another sound (like a click) that seems to be coming from the tank area, but no a sound that I would call a fuel pump hum. You are correct, I did use a voltmeter because I didn't get any indication on the test light.
Thanks,
Tony (aka cobraf250)

 

You need to ground pin#6 of the test connector with the key on and see if the fuel pump relay clicks as you ground and un-ground pin #6.
If the pumps run when you ground pin #6 you need to put a fuel pressure gauge on the fuel pressure test point on the fuel manifold. It should read about 45 PSI.

Here is a diagram of test connector, your wire color is different.
http://i54.photobucket.com/albums/g91/subford/Fuel/DataLinkConn.jpg

And a diagram of your fuel system.
http://i54.photobucket.com/albums/g91/subford/Fuel/FielSystem.jpg

The electrical system:
http://i54.photobucket.com/albums/g91/subford/Fuel/Fuel-sel1990F150.jpg

 

No luck. The relay kicked in but the pump did not run.

 

I take it you only have one fuel tank. You say you have power to the fuel pump relay but what wire?
If it is the red wire this is just power to the coil of the fuel pump relay and the PCM grounds the other side (pin #6 of test connector) to turn on the fuel pumps.
The Yellow wire is the power wire for the fuel pumps that the relay sends on.
Is the Yellow wire hot?

 

There are two fuel pumps, but the front one has not worked since we have had the truck so we have jsut been running off the back tank. The guy I bought the truck from said that the front tank quit years ago and the gas in the tank was just as old. I did check the wires with a light tester and with the switch off I had nothing on the red wire and 12 volts on the yellow wire. With the switch on I had 5 volts on one of the red wires, 12 volts on the other red with 12 volts on the yellow.

 

The other red (more than likely the brown one) with 5V on it was this with the relay in and the pin #6 grounded at this point?

 

No. All checks was without the relay in.