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94 4.0 Start, dies, run with MAF disconnected

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  #16  
Old 08-22-2011, 09:42 PM
pawpaw pawpaw is online now
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P0538 = A/C Evap Temp Sensor Circuit High.
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  #17  
Old 08-22-2011, 10:34 PM
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Ok.. Here is the latest.. I went out, refired the truck. got the code to clear by running it. It finally failed again, got a new code...

542: Fuel pump circut open, PCM to Motor.

Connector from main harness to PCM is clean and good.... PCM garbage??
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  #18  
Old 08-22-2011, 11:27 PM
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My next question...

Will a PCM from a 94 Explorer with the same engine, trans and 4x4, work on my Ranger?
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Old 08-22-2011, 11:55 PM
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Check the under hood power distribution box fuel pump power relay. Maybe give it a thump & see if it'll wake up, or swap it out for a like relay not needed to run the engine, like the A/C power relay & see what happens.

If no joy, check the in cabin fuel pump inertia switch to make sure it isn't tripped.

If thats ok, use your multimeter to check for B+ to & through the inertia switch for two seconds at KOEO. If you have B+ there, look for a wiring or connector problem between the inertia switch to the fuel pump.

If no B+ there, go back to the under hood fuel pump power relay & check for B+ to & through it & for a voltage from the computer at KOEO to operate the fuel pump power relays actuating coil. If no power there, back up to the computer firewall connector & check for B+ there. If no power to the fuel pump relay from the computers firewall connector to operate the fuel pump power relay, then suspect the computer.
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Old 08-23-2011, 10:02 AM
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Quote:
Originally Posted by pawpaw View Post
Check the under hood power distribution box fuel pump power relay. Maybe give it a thump & see if it'll wake up, or swap it out for a like relay not needed to run the engine, like the A/C power relay & see what happens.

If no joy, check the in cabin fuel pump inertia switch to make sure it isn't tripped.

If thats ok, use your multimeter to check for B+ to & through the inertia switch for two seconds at KOEO. If you have B+ there, look for a wiring or connector problem between the inertia switch to the fuel pump.

If no B+ there, go back to the under hood fuel pump power relay & check for B+ to & through it & for a voltage from the computer at KOEO to operate the fuel pump power relays actuating coil. If no power there, back up to the computer firewall connector & check for B+ there. If no power to the fuel pump relay from the computers firewall connector to operate the fuel pump power relay, then suspect the computer.
I will run the test and see what I find out there!

I had replaced the Inertia switch, along with the fuel pump, fuel pump relay, fuel pressure regulator now, fuel filter, MAF, and vacuum lines. Everything so far under the hood (with the exception of some dry rotted vacuum lines) has turned out pretty clean.. So i am eager to see what happens next!

IN case the PCM is bad, is it possible to use one from a same year, engine, trans, drivetrain Explorer? I have a lead on one for a good price, now that I have dumped all my money into those other parts, LOL!
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  #21  
Old 08-23-2011, 01:27 PM
Rangerlvr Rangerlvr is offline
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Most explorer parts will fir the rangers, if in doubt cross check parts numbers
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  #22  
Old 08-25-2011, 09:23 AM
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Looks like I will have to give it a shot then! LOL
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  #23  
Old 08-25-2011, 11:33 AM
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Hold ON....before buying a computer, at KOEO does/can you hear, the fuel pump run for two seconds to build fuel pressure & cut off?????
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  #24  
Old 08-26-2011, 01:23 AM
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Yes.. Turn the key to the "On" position, you can hear the fuel pump nice and loud, whine for a couple seconds, then goes quiet.

This means its working correctly? Right?

I do have a brand brand brand new fuel pump in it, as well as relays, inertia switch, fuel pressure regulator, fuel pump relay, MAF, and vacuum lines.
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Old 08-26-2011, 07:42 AM
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Yup, if you can hear the fuel pump run for a couple of seconds at KOEO, thats good.

NOW, back to the P0542 code you posted, it's a good clue, the definition I have for this code is, Fuel pump circuit open, ECA to pump motor ground.
It seems the computer has detected an Intermittent open circuit, some where along the way & you need to do a "wiggle" test with the engine running to see if you can induce an open circuit & engine stall.

Is your Ranger a super cab model by chance???? If so, check the wiring & electrical connector under the drivers seat, where the wiring goes through the floor board. There is a TSB repair out for wire insulation chaffing & shorting out there. Rockledge posted photos from underneath, on his super cab repair in that area, some years back, a forum search should turn it up. Maybe if he's monitoring this thread he'll post a link to it if you have the super cab model.

More thoughts for consideration, keep us posted on your trouble shoot.
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  #26  
Old 08-26-2011, 08:27 AM
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Hearing the pump is good. However, it should be hard to hear. If it whines it is probably failing.
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Old 08-26-2011, 10:03 AM
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Quote:
Originally Posted by pawpaw View Post
Yup, if you can hear the fuel pump run for a couple of seconds at KOEO, thats good.

NOW, back to the P0542 code you posted, it's a good clue, the definition I have for this code is, Fuel pump circuit open, ECA to pump motor ground.
It seems the computer has detected an Intermittent open circuit, some where along the way & you need to do a "wiggle" test with the engine running to see if you can induce an open circuit & engine stall.

Is your Ranger a super cab model by chance???? If so, check the wiring & electrical connector under the drivers seat, where the wiring goes through the floor board. There is a TSB repair out for wire insulation chaffing & shorting out there. Rockledge posted photos from underneath, on his super cab repair in that area, some years back, a forum search should turn it up. Maybe if he's monitoring this thread he'll post a link to it if you have the super cab model.

More thoughts for consideration, keep us posted on your trouble shoot.
Yes, it is! I noticed that seems to have to do with a lot of things when it comes to getting parts, LOL!

I really need to check that out then. Very fascinating!!! Thank you for the heads up there as well! For the sake of understanding things, why is it this happens when it gets to be over 90 degrees out? Maybe coincidence?

Is this wiring inside the cab, or along the chassis under the cab?

This whole thing has me going insane! I have put so many new parts in this thing, and its not running.. Thats not a good thing!

Kahn.. Its not whining as much as I just here is spin up and do what its supposed to,
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  #28  
Old 08-29-2011, 01:18 PM
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Ok.. Just to update, I havent had a chance to check it out as I had to leave the truck in another town until I could get back to it to work on it. I am planning on limping it in tonight when the temps are lower. I will also be checking that wiring "under the drivers" seat, LOL! The KOEO test for the Computer to relay will have to hold off until I get it back.

Something about this all is ambient tempature related I am guessing, but can be more specific when I get back tonight!
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  #29  
Old 09-02-2011, 10:55 PM
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Latest news... So I drove it back home the whole 65 miles to the ranch, no issues! Of course this was late at night, and a lot cooler outside!

I first checked under the drivers seat for the wiring issue.. No wires under there.. at all. I cut the carpet open too, nada! The only set of wires, were the two wires to the seat belt indicator.

I checked under the hood. PCM to Power Distro box, To harness through chassis, to rear of vehicle. Wiring was in good order. Wiggle tested each connector. I also put in new dialectic grease at each connection point.

Inertia switch tested good again.

Power relay B+ came across good and uninterrupted.

Power coil relay for fuel pump tested good. No interruption.

Here is what I have noticed. Every day the outside temp is about 90 degrees, I have this issue and more so with the AC on. I get vapor locked every time going down the road. I think what is happening is that there is an issue with the ECU/PCM that acts up when the computer gets hot.

I have replaced all FUEL Parts.. Every single one of them, from relays, to pumps, to intertia switches, to regulator, so on and on.... Still no change.

I have replaced every single vacuum line, including installing these cute sealer clips to prevent vacuum leak.

I have replaced the MAF twice, no change.

The data connector and code reader at the parts house.. no luck. PIN test myself, I have luck.

After reading what is going on with Antiquynots truck, I am going to go ahead and get a used PCM/ECU from a donor Explorer of the same year and specs. If this does not solve the problem, it will be time for my back up plan..

I will strip the entire fuel delivery system including fuel delivery lines from the truck. I am going to fab up new lines, run them outside the chassis rail, and install a Holley Performer Rail Fuel pump and filter. I will loop the factory fuel pump back into the tank to simmulate the circuit for the ECU, but will hold no function there after. With this, I know I will be guaranteed fuel delivery at a high PSI.
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  #30  
Old 09-08-2011, 01:24 PM
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Midwest Dually,
I don't know if this will pertain to your situation, but ... a friend who is very Ford knowledgeable advised me to check the electrical connection at the fuel pump/sender assembly. These are a known failure point. I believe he said that Ford has a kit to address this problem. He ran into a situation where a customer with a Ranger came in with a "no fuel pump action" problem, he replaced the pump. Two months later, the customer was back with the same problem. Thinking he had gotten a defective pump, he placed it again. Two months after that, customer back with same problem. At that point he started looking more carefully and found that without reaching up to the assembly first, he lifted the bed and found that if he did a "Wiggle Test" on the wires, he could recreate the problem. That's when he found out about the Ford recall/TSB. As with mine, perhaps you have more than one problem. Just my $0.02,
Tony
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95, air, code, disconnected, flow, fuel, idle, maf, mass, p0542, run, runs, sensor, taurus, truck, unplugged

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