Fuel Pump? MAF? - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 02-06-2012
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Icon4 Fuel Pump? MAF?

I have been having trouble with my 94 4.0. Sometimes the fuel pump wont kick on (so it wornt start). Other times it will run fine for a while but then while I am driving it will start bucking, kicking in and out of power. I get a dead pedal and loose power.

I thought for sure it was the fuel pump because it wouldn kick on when I turned the key to ignition. Then I went out last night and it did kick on, the truck started runnig bad. So I unplugged the MAF sensor and it started running better. I had changed the MAF last summer but I thought it was defective. I borrowed my brothers MAF and it still runs bad unless I unplug it. Any connection between the MAF and fuel pump? I had gotten to the point where I thought for sure it was the fuel pump, but now that I unplug the MAF I am not sure.

I have already changed the relay and fuel filter. Any suggestions?
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Old 02-06-2012
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Are you running a K&N filter ? Right out of the box they are over oiled and screw up the MAF.
Get some MAF sensor cleaner and try cleaning it first.
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Old 02-06-2012
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No I am running the OEM Fram filter. I have tried the MAF sensor cleaner on mine. It didnt work. So I took the woking MAF out of my brother's truck and it did the same thing.

Thanks,
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Old 02-06-2012
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Trace the wires from the MAF to the PCM , check every inch for a broken/bare spot.
Unbolt the battery cable and remove the connector to the PCM and check for corrosion.
It's a 94 so I suspect water got in there by now and there's a bad connection or a wire has worn through by rubbing on something.
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Old 02-06-2012
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Wow thats gonna take some time. Any other ideas incase the wiring turns out to be good?
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Old 02-06-2012
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Here's a thread That I keep bookmarked.
https://www.ranger-forums.com/ranger-forums-office-13/i-think-we-need-glossary-trouble-codes-58160/

You can pull the codes yourself and see what comes up.
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Old 02-09-2012
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Well since I havent got a code reader and cant get it to Advance, let alone find the time to trace the wiring harness. Does anyone have any other ideas of what it might be? Could it still be the fuel pump even though it starts sometimes when you turn the key and it runs better with the MAF unplugged?
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Old 02-09-2012
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If you read down the link I posted , you don't need a code reader for 94 and older. You can read the codes using a jumper wire and a voltmeter.

http://www.troublecodes.net/Ford/
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