92 F150 with code 542 (somewhat long post)

[Chrono558]

First of all this isn't mine and I'm going to ask here instead of the other site first. Vehicle is a 92 F150 with a 4.9 I6 4WD.

This truck has been sitting for a year without being started while the owners neighbor tried to "fix" it for a no crank/start issue. We got it towed back to the dealership I work at (I'm the only one who will work on a ford in a chevy dealership go figure. And yes I do own a F150 of my own ) Anyways... the neighbor replaced the starter and solenoid and after I let the battery charge all night it would crank just fine but now no start. I hook my code scanner up and get 542 - Fuel pump circuit open - etc.,.

Now the truck will start and run on carb cleaner which is a good sign especially for sitting over a year. I'm not hearing the pump cycle on when the ignition is first turned on so we know we're not getting fuel for sure. Now I have checked the fuel pump relay and it's clicking on and off like it should. I've tried grounding the blue/orange wire on the eec test plug and cycling the ignition to see if the pump will turn on then and it still won't.

So at this point I'm suspecting a bad pump or the pump is not getting power. What needs to be checked before I drop the tank (thankfully it's only one tank.) My other question is on the code 542 I've read from several sources that the "Fuel pump circuit open" but the second part never agrees i.e. EEC processor to motor ground, inertia switch, etc.,. Does anybody know what the Ford definition for this code is? Thanks.

 

[lenny1carl]

there is another relay in there identical to the FP relay. try it. i had a FP relay that clicked but wasn't actually pulling in

 

[conanski]

Check the fuse and inertia cutoff switch in the passenger kick panel I believe, and after that it comes down to dropping the tank and checking that you have voltage at the fuel pump connector. If you do then the pump is the problem.

 

[Chrono558]

I did check the inertia switch and it wasn't tripped so now I'll drop the tank tomorrow and see what we got. My only problem with that is when unhooking the filler neck from the tank there's that smaller hose inside of it and last time I had to drop one I never could figure out how to get all of that out without cutting the smaller hose in half. If someone has a tip on how to work around that that'll be great.

 

[Lost]

The inner will / should slide out of outer hose. You can take big hose off at filler and feel all between frame and bed. Good luck

 

[Chrono558]

UPDATE #1

Got the tank dropped today (thanks for the tip Lost) and after digging around on mitchell for a wiring diagram (no such luck) and then by one subford posted on the other site, I'm getting 12v on the brown/white wire and using the orange wire which I believe is the pump ground. Now what I did notice is when the pump is commanded on (cycle ignition) that it will read 12v but when commanded off it drops down to around 6-7v. Is that normal for it to do that?

 

[Raptor22]

UPDATE #1

Got the tank dropped today (thanks for the tip Lost) and after digging around on mitchell for a wiring diagram (no such luck) and then by one subford posted on the other site, I'm getting 12v on the brown/white wire and using the orange wire which I believe is the pump ground. Now what I did notice is when the pump is commanded on (cycle ignition) that it will read 12v but when commanded off it drops down to around 6-7v. Is that normal for it to do that?

Nope, shouldnt be. Umm... wow. Could there be some kind of short or electrical problem? Alternator?

 

[subford]

UPDATE #1

Got the tank dropped today (thanks for the tip Lost) and after digging around on mitchell for a wiring diagram (no such luck) and then by one subford posted on the other site, I'm getting 12v on the brown/white wire and using the orange wire which I believe is the pump ground. Now what I did notice is when the pump is commanded on (cycle ignition) that it will read 12v but when commanded off it drops down to around 6-7v. Is that normal for it to do that?

Sounds like you are using a meter, do not use a meter in the fuel system wiring, as they do not load the circuit. Use a bulb type test light to load the circuit so you know what you have.
Your 6-7V is more than likely zero volts.
If your test light lights when you probe from the "BR/W" wire to the "O" wire and the pump does not run you have a bad fuel pump inside the Fuel Delivery Module (FDM).
If the test light does not light then varmints may have ate the wire to the ground point at the radiator support.

My other question is on the code 542 I've read from several sources that the "Fuel pump circuit open" but the second part never agrees i.e. EEC processor to motor ground, inertia switch, etc.,. Does anybody know what the Ford definition for this code is?

You did not say which 542 code you got, KOEO or CM.

I will guess that it is CM so here is what Ford says about CM 542 but if you got a 542 KOEO post back and will relate that one.

A Continuous Memory Code 95/542 indicates that one of the following intermittent conditions has occurred:

-- Fuel pump circuit activated when processor expected circuit to be off (i.e. fuel system test or prime procedure).

-- Open circuit in or between the fuel pump and FPM circuit at the processor (refer to «schematic»).
-- Poor fuel pump ground.
-- FPM or Power-To-Pump circuit short to power.
-- Fuel pump relay contacts stuck closed.
-- Left/Front HEGO circuit short to power (dual HEGO).

Start engine.
Check for engine stall/stumble while performing the following (also, if possible, listen for fuel pump turning off.)

- Shake, wiggle, bend the Power-To-Pump circuit between the Power-To-Pump pin at the fuel pump relay and the fuel pump.
- Shake, wiggle, bend the fuel pump ground circuit from the fuel pump to ground.
- Lightly tap the fuel pump to simulate road shock.
- For vehicles with the inertia switch in the Power-To-Pump circuit (refer to «schematic»), lightly tap inertia switch to simulate road shock.

Key off.
Inspect the fuel pump vehicle harness connector and the fuel pump ground for corrosion, damaged pins, etc.

/

 

[Chrono558]

UPDATE #2 (posting from work)

I was wondering if the DVOM was throwing off the reading since it didn't load the circuit enough. Rechecked it with a test light and got better results. Installed a new pump and lever sensor and spliced in the new harness that Ford sent me with the pump and she started on the first try. Then I was greeted with an awful screeching noise from the engine from the idler pulley being siezed. So one more fix and then off for a test drive. She survived that and the owner didn't want me to do anything else to it (it needs a lot of TLC done to it.) Anyways, thanks for all the advice guys; it came in very handy.



Oh and subford, the 542 was in both KOEO and CM when I scanned it the first time.