Fuel pump i think

[Ford-O-holic]

I get a code 543 out of the ole Explorer and am at a total loss as how to fix it or if the fuel pump is toast, but it still runs almost fine. Code 543 = Fuel pump monitor circuit shows no power - Power / Fuel Pump Circuits. Can somebody help me out here. A million thanks.

 

[Ray Lobato]

Sounds like the sense line coming back from the fuel pump to the computer is open.
Find that line and you have found your problem. It sound like your computer thinks that the fuel pump is dead, even though it is not.

 

[Brett]

Did you ever determine the cause of the fault code 543? I've been chasing this on a 94 for 3 months now. It's been to Ford, and 2 independant repair shops.

Symptoms include:

Start and stall
rough idle
stall at stop lights
spudders at rpms under 2500
driveability issues

What I've done:
Replaced O2's
Cleaned MAF
Cleaned throttle body
Replaced TPS
Replaced spark plugs and wires
Replaced Canister purge solonoid (needed to be done anyway)
Replaced fuel filter
Replaced FPR
+some other stuff I haven't kept track of.

What I'm goning to do this week:
Swap EEC
Swap Relays
Cut harness apart and inspect wiring from relay to eec
drop tank and inspect wiring
check grounds

ANY suggestions would be VERY helpful at this point.

Thanks,

Brett

 

[DeagleDave]

i don't know if it applies to Xplorers but isn't there a fuel cut off switch somewhere? maybe that switch is faulty. or perhaps the wires to your fuel pump aren't plugged in securely

 

[Brett]

I don't think so. It's a wierd problem b/c it runs like a champ at anything over 2500 rpm.

 

[DeagleDave]

are you sure plugged are gapped right? i gapped mine to .50 to eliminate some hesitiation. was it the mileage on your X? maybe it's just time for a fuel pump change. or have you looked for a vaccum leak?

 

[Brett]

plugs are gapped right. no vacuum leaks. fuel pressure is consistant (don't remember what it was, but it was tested). Milage is 91K. Truck was rear ended and a week later this all started and has got consistantly worse since (this may just be coincidence)....

Ford says "possible wiring problem at splice in fuel pump circut"

Has anyone seen this before???? Searches have turned up no answers..

Brett

 

[DeagleDave]

check that fuel cut off relay....ford has em that rear ending may have activated it or it may have developed a short

 

[Brett]

Problem solved!!!! EEC is bad. Swapped it out with another one and everything works great!