Fuel pressure problems - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 03-09-2009
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Fuel pressure problems

New to site.Did a search and didn't find a answer to my problem.Have a 93 ranger s/c 4.0 auto.Here's the problem,installed new fuel pump,relay,and new fuel pressure regulator.When I turn the key to on,the fuel pump keeps humming and won't stop.Sometimes the engine will start but idles very rough and seems like it's only hitting on a few cylinders.The check engine light is on.Every once in awhile it will just make a noise and then it is running correctly.It might run okay for a day or just a few minutes and then the engine light comes on and it starts idleing real bad and running bad. Had it scanned and it showed a code of 167,throttle position sensor.Replaced the sensor and it still does exactly like I have stated.I've put on two new fuel pumps and two new fuel pressure regulators.I now have no clue on what is causing this.The only other thing is that the ignition cylinder with the key is a little loose.Does anyone have any ideas on what is causing this and how to fix this problem?All info will be greatly appreciated.Thanks,Clinton in okc,ok.
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Old 03-09-2009
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Can't help much except this..

Dis connect the battery, turn on the headlights.
Turn them off and reconnect the battery.
Turn on the ignition and then floor it twice.

Then start the motor.

That will make sure the TPS is being seen correctly and it'll reset the PCM.

If it's still rough... then I'd put a fuel pressure guage on the fuel rail to verify it's within spec.

Rich
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Old 03-09-2009
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Quote:
Originally Posted by wydopnthrtl View Post
Can't help much except this..

Dis connect the battery, turn on the headlights.
Turn them off and reconnect the battery.
Turn on the ignition and then floor it twice.

Then start the motor.

That will make sure the TPS is being seen correctly and it'll reset the PCM.

If it's still rough... then I'd put a fuel pressure guage on the fuel rail to verify it's within spec.

Rich

i've never heard of something like this... whats the reason for turning on the headlights... wouldnt just disconnecting the battery and waiting a few min. reset the PCM?
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Old 03-09-2009
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Disconnect the positive and negative cables?
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Old 03-09-2009
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Waiting a few minutes.. yes.

Either way, just disconnecting the battery for a minute is not enough.
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Old 03-09-2009
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I tried it but I didn't wait very long.Still did the same thimng.So I need to leave the battery disconnected for at least 5 minutes and then retry?This is acting so weird.Two fuel pumps can't be bad or two fuel pressure regulators.Sometimes the fuel pump does hum for a few seconds and then quits and the truck runs fine.Then it will act up even when it was driving ok.Where do you hook up the fuel pressure gauge at on the engine? Thanks a bunch for the help guys.I'll let you know how the longer disconnect did after I get back from running some errands in the car.
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Old 03-09-2009
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On your fuel rail there should be a threaded port. It looks just like the valve stem on a tire. (usually a screw on plastic cap on it)
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Old 03-09-2009
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My guess is a crack in one of your fuel lines. May not even be visible. But when flexed a certain way (acceleration, stopping, turning.....whatever) releases fuel pressure from the system and causes your problem.
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Old 03-09-2009
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Battery disconnect didn't work.Fuel pump still runs when key is in the on position.Pulled FP relay then turned key on,no sound of fuel pump running at all.Switched relays,pump still runs without shutting off.Engine will start but idles very bad.No gas leaks anywhere under the truck.Trying to figure out why the fuel pump keeps running and doesn't stop.Looking at something electrical maybe.Keep helping if you have any other ideas guys.Thanks a bunch.
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  #10  
Old 03-15-2009
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Fuel pressure checked.It is OK.Changed out Mass Flow Air.Still hasn't fixed problem.When ignition key is turned on,the fuel pump keeps running and the truck won't start.Pulled the fuel pump relay.Fuel pump does not come on when turned to the on position with key.Truck justs cranks and won't start.I'll check to see if I'm getting any spark to the plugs.But a bad coil shouldn't make the fuel pump keep running should it?Any help will be appreciated.Thanks guys.
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Old 03-15-2009
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You PM me but honestly i dont know what the issue is i would have to see it in person start trouble shooting the wiring i would think
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Old 03-15-2009
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Thanks for the reply redneckstone.Guess I'll need to check for a short in the wiring.Earlier after about 6 times of turning the key to the on position the FP came on and then quit.Truck started up and ran ok for about 2 minutes.Then it started to idle real bad and check engine light came on.This is absolutely nuts!!! I've been told that the pcm does not make the FP keep running when key is turned on. Can't imagine that it's a short in the FP wiring.Something is making it idle and run bad and then it will run good at times.I will get this problem fixed and let you know what was causing it.Any thoughts and/or suggestions will be appreciated.
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