Fuel pump not working

Tiny
MHJ2756
  • MEMBER
  • 1994 FORD F-150
My truck will not start. I am sure it is fuel delivery problem. It has dual tanks 5.0 engine. I do not have any power at the front or rear tank connectors, rear tank has never work their is no power at the selector switch or at the inertia switch. There are four relays mounted next to the power distributor box. I change them around, I checked all fuses. I also grounded the lead of DLC connector had the same problem. One other time I keep turning the ignition off an on until I heard the fuel pump come on. Thanks if you could help me with this problem.
Do you
have the same problem?
Yes
No
Wednesday, October 15th, 2008 AT 2:55 AM

8 Replies

Tiny
JAMES W.
  • MEMBER
Do you have battery voltage at fuel pump relay socket? Can you hear the fuel pump run for just a few seconds when you turn the key to "on"?

Here is a guide to help you test to see where you are losing power along with the engine and fuel pump wiring diagrams so you can see how the system works:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

I have seen the fuel pump switch valves also cause this problem FYI.

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

Cheers
Was this
answer
helpful?
Yes
No
+2
Wednesday, October 15th, 2008 AT 3:35 AM
Tiny
MHJ2756
  • MEMBER
There are four relays I think I have 12 volts at all of them. I cannot hear any noise from the fuel pump. Also, I have replaced the ignition switch.
Was this
answer
helpful?
Yes
No
Wednesday, October 15th, 2008 AT 6:02 AM
Tiny
JAMES W.
  • MEMBER
I am sorry, but "thinking" you have power to the relays does not do me much good. Let's do it this way.
One of the relays of the four will have the following color wires. My diagram does not tell me which one for sure, but look for these colors. These are the wires going to the relay socket.
1- Yellow-12 volts from the fuse. No power, the fuse is out.
2- Dark green/yellow-power to inertia switch. From inertia switch to fuel tank selection switch, then to fuel pumps.
3- Red-12 volts from computer when key in "start"position. Not "run", start position.
4 Blue/orange-ground from computer with key in "start" position.
Test; jumper wires 1 and 2. You should now have power to the inertia switch, the sector switch and which ever tank is selected, that pump should be running.
If not, check power at fuel pump connection at tank. If you have power there, the pump is bad.
Was this
answer
helpful?
Yes
No
+1
Wednesday, October 15th, 2008 AT 8:58 PM
Tiny
NATASHA30122
  • MEMBER
We are having the same problem on our 1994 Ford F150 single tank. No firing and no fire to the fuel pump. Please respond where the fuel relay is located. Is it under the hood or in the truck? Which relay is it? Thank you! Robbie C.
Was this
answer
helpful?
Yes
No
Sunday, October 26th, 2008 AT 2:52 AM
Tiny
NATASHA30122
  • MEMBER
I had to replace the switching valve like you said everything working great now. :)

Thank you so much for your help.
Was this
answer
helpful?
Yes
No
Sunday, October 26th, 2008 AT 2:55 AM
Tiny
KEN
  • ADMIN
These trucks had a big problem with the switching valve which is located between the tanks on the frame rail on the drivers side.

Please let me know how it goes, we are here to help.

Best, Ken
Was this
answer
helpful?
Yes
No
+1
Tuesday, August 16th, 2016 AT 9:35 AM
Tiny
RACE STREET
  • MEMBER
I have been trying to figure out why my rear tank quit working. I just replaced it then a week after it cut out on a hard turn. Front tank works. Replaced relay and inertia switch. I cannot hear pump come on either.
Was this
answer
helpful?
Yes
No
Saturday, July 28th, 2018 AT 11:43 AM
Tiny
STEVE W.
  • EXPERT
RACE STREET Could you please use this link https://www.2carpros.com/questions/new
and ask this as a new question, please give all the information you can as well as what you have done to try and repair the issue. Thank you
Was this
answer
helpful?
Yes
No
Sunday, July 29th, 2018 AT 7:37 AM

Please login or register to post a reply.

Recommended Guides