I have a 91 f150 with 302, and about two months ago I change the fuel pump, and then the relay because both went bad. Now I have no power to the pump, but I have power to the gauge and also my relay. Does anyone know if something else would be causing no power to get to the pump other then the wiring? I would like to role out all electrical component first before tracing hundreds of wires. Thnx for any imput.

 

I would check the eec relay connection,and the fusable links. Does check engine light come on with key? Theres 4 0r 5 fusable links at the starter sol, and one on the driverside by the relays. Also there is two grounds that tie into the neg terminal at battery,that have to be connected. One more place to check is the inertia switch by the brake pedal

 

Do you hear any clicking and other such noises under the hood when you turn the key on? If not your ECU may be dead.

 

Ok I checked the pump first, and it runs but no power at my plug. Then I check the inertia switch and that tested good, also the fuel pump relay is putting power out to the other terminals. And when I turn on the key there's a click and in about 3 seconds I here another noise. (The click is the fuel pump relay then there's a pause when the pump should run, then when it should turn off there's another noise) So this makes me wonder if my computer componets are ok? I'm almost positive there was power at the EEC relay but I can't remember I haven't worked on for two days, but if the fuel pump relay has power won't the EEC supply it? Thanx for your reply.

 

Also I forgot to mention when this all started, friday evening I was driving to town on the back road where it's bumpy and the truck started cutting out every few seconds then it would come back, and it was only when I was in a high gear but I made it home. So saturday I got plug wires and a cap and rotor, because they had motorcraft on them and looked like the original, and they were britle. Then monday after school on the way home on the back road it started the cutting out then it died completly, so I restarted it fired up and went 20 ft and it died again, so I thought maybe a loose wire at the pump and crawled under and just before I touched the wires the pump ran for a few seconds and kicked off, so then the truck went 20 more ft then died and I had to call my dad and tow me home. Then got it in the garage and hit the key and the pump ran so I let it run and the next day went out and it's wasn't running again. Now it won't do nothing.

 

The EEC relay does have power, and with the key on it's only putting power out to one of the wires, so I'm guessing the other wires on the relay are grounds?

 

If you have power leaving the inertia switch and non at the plug for the fuel pump check the selector switch on the dash or if one tank check the fuel pump selector jumper at the dash.

The EEC Power Relay puts power out on the red wire to the coil of the Fuel Pump Relay and the Computer grounds the other wire on the coil of the Fuel Pump Relay to pick the Relay.

The Yellow wire on both the EEC and Fuel Pump Relays is power from the battery to the output of each Relay.

 

I did check for power at the duel tank switch before and there is power there, and I just checked for power at the inertia switch and I'm not getting any power with the key on? Where does the power suppy for the inertia switch come from? Thanx this helps alot.

 

when you checked for power at the dual tank switch did power switch from one wire to the other when you switched tanks ? if power switched then the tank selector valve will be bad !

 

I would almost bet it is either the eec or fuel pump relay connector. Try moving around the wires with the key on.

 

yes power switched from different wires but the wires that switched were the gauge wires, the other wires for power to the pump didn't have power in them so it must be before that swith? Which gets power first the tank switch or the inertia switch? Thanx

 

The Inertia switch feeds the selector switch.
The Fuel pump relay feeds the inertia switch.
The fuse link at the starter solenoid feeds the Fuel Pump relay over a Yellow wire.

What are you checking power with?
You can only use a test light with a bulb in the fuel pump circuit to check for power, a meter will not work in this circuit.
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Yes i'm using a snap-on test light, but I used the meter to check the inertia switch for continuity. So since the relay supllies the inertia switch with power and there's no power there then I must have a bad wire? Looks like I'm tracing wires tonite!

 

Well I figured out the problem, I cut the tape on the wiring and I found the green with the yellow tracer, which is to the inertia switch and runs to the EEC relay. And this had no power and as I was looking for where it went had broke a wire of the fuel pump relay, which was corroaded so I tested for power there and i had power like on the tests before, but I guess the wire wasn't getting the power? So I hooked a jumper up and ran it to the broken wire and sometimes I would get power through. So I striped the wire and cleand the connecter some to get connection and now the pump runs and it starts. So I just need to replace the fuel pump relay connector and I should be good. deeznuts822 was right, and I did move the wires but nothing happen so I traced wires and that's when I broke that wire on the fuel pump relay. Thanx for the help everyone!

 

There is no green wire with a yellow tracer in your fuel system wiring.
Also there are no wires that run from the inertia switch to the EEC relay.

However bad connections are a problem on the bottom of both the Fuel Pump Relay and the EEC Power Relay sockets from 1985-1991.