My code reader says 556 fuel pump relay. I can not find the relay, there is no relay holder on the left (driver's) side fenderwell, I have no clue on where this puppy can be found. can any one help?

1992 F-150 I-6 302,000 miles first time it has failed to run.

 

I double checked the book and it said on early and late models it was located on the left(drivers) side fenderwall apron (relay and housing assembly). If it is not running also check your fuel pump inertia switch. If this switch has been tripped it cuts the fuel off between the relay and the pump.

 

Thanks for the quick reply, but there is no relay or relay holder on the fenderwall of this truck.
I have a power distrabution box which houses the secondary fuel pump relay (replaced) but now primary.
the only thing attached to the fender area is the three attachment plugs for code readers. It's just not there or it is under someting.
But thanks
Craig

 

took out both rt and lft side kick panels not relay, removed air box no relay, all the wires in the firewall fender corner (left/driver side) are massive plugs thru the firewall with retaining bolts. there is just no relay's anywhere to be found.
This is a California truck, made in Canada so maybe they did it differant for this wacked out state. Will stop by the local dealer tomorrow and see if they will have some insite on this missing relay.
thanks

 

There is only one fuel pump relay, and it is in the power distribution box, which you have already found. The primary circuit is the circuit from the computer to the relay that activates the relay, and the secondary circuit is the switched power wire that goes to the fuel pump(s). If you have dual tanks, does it run on one and not the other, or neither? This code could also indicate a failed fuel pump, a tripped inertia switch, or a blown fuse.

 

epncsu2006
thanks for the reply
No it doesn't run on eather tank. And did not start when I replaced the 1st relay.
Was running fine, then stalled like it was out of gas, restarted and stalled a couple more times, when I got it running I had to drive with very little gas pedal movement, real eazy accleration. Got to job site, and two hours latter would not start.

Autoparts store sold me a large relay, and doesn't even list the small one, found it under trailer backing.

As I recall the fuel pumps are in the tank and both have to be replace at the same time.

thanks for your help.

 

Try the inertia switch first, before going and buying fuel pumps. It would be pretty odd for both to fail at the exact same time. It could be the relay; I'm not sure which one you replaced - it should be in that power distribution box, and the owners manual or the lid of the box should tell you which one it is. If you have a multimeter, you can check for voltage at the fuel pumps to see if they are getting voltage. There is a wire in the diagnostic port that you can ground to force the fuel pump relay on. If you don't hear it click, there is a problem with the relay or the wiring to it. If you hear the relay click but have no voltage to the fuel pumps, then check the inertia switch under the passenger side kick panel, and the tank selector switch in the dash. Basically trace the fuel pump power supply wire through all of the joints and switches until you find where power is interrupted.

 

If it was the inertia switch then he would have never been able to drive it that little bit.

 

Yes that's true, but it takes 5 minutes to check, and it could have been tripped in the meantime. It also wouldn't cause the intermittent and sluggish nature, but the basics must be checked before just throwing expensive fuel pumps at the problem.

 

Relay replace and can hear the pumps, put a pressure gauge on the engine side of new fuel filter and read only about 10-15 psi with key on, if I turned the key on and off a number of times the pressure built up to 40 psi. on the front tank.
No fuel from the rear tank.
The truck will run but if you put it under load, drive forward it stumbles and dies.
If it wasn't EFI I would think I had a bad acclerator pump.

I am going to warm up the truck and run the codes again.

 

Check the voltage at the tanks with the pumps running by jumpering the fuel pump lead on the diagnostic connector to ground. If it is less than 12V by more than a couple volts, it is likely mostly a wiring problem. The fuel pressure is definitely too low, find out why.

 

Thanks I will check it out sunday, as I have to head back up the mountains tonight, as I am a Park ranger most of the time.
Will let you know what I find
Thanks again for all the help, This is a great site.
Craig

 

If he isnt getting any new codes after replacing the relay and the fuel pump and now has low fuel pressure and engine dies under load--wouldn't this possibly point to an partly blocked fuel filter?

I had a 88 F150 that had the same symptoms--would die under load only--and a new fuel filter ,in the frame under the driver's seat, fixed the problem.


Oops--just noticed in his last response that he already replaced the fuel filter.

Never mind!

 

That was my first thoughts also.
Q: What happens if you install the filter backwards? Will it even fit?

Popa Tim

 

the switch on the dashboard went out on me and gave me the same trouble,replace the duel tank switch