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Discussion Starter #1
Good afternoon everyone,
My bronco devoloped a fuel issue I need help with. Here is the background:
The fuel pump normally makes a loud whining noise when running and at initial start up. Yesterday while driving the truck started "bucking" and backfiring through the intake while driving about 30mph. When you come to a complete stop and try to accelarate, it bucks, backfires and will stall if I dont let off the gas pedal. I turned it off and when I tried to restart it I noticed the fuel pump made a low "growling" sound, much different than it normally does. I got it home and checked fuel pressure at idle and it was about 26psi. I replaced the fuel pump and filter and it ran better for about five minutes then it went back to running bad, exactly the same as with the old fuel pump. I also noticed that this pump makes a low growling sound when you start the truck cold. After warm up, fuel pump sounds normal, even if it gets turned on and off. The truck does run better after warm up but, it still runs rough.
I pulled codes after the truck was warmed up and this is what I got with engine turned off: 565, 1(??) and 172.
With the key on, engine warmed up I get these: 538,536 and 632.
The gas tank did have a little bit(about a teaspoon) of some black powder. When I dumped the filter out it didnt seem to be clogged or have any of said powder.
Any help with this issue will be greatly appreciated.
 

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did you happen to check the pickup on the pump to be sure it was clear?
 

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536 was because you did not press the brake pedal
538 is because you did not do the WOT test
565 is canister purge failure
632 Overdrive cancel switch not changing state
172 is your O2 being lean, this can be caused from low fuel pressure.
 

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there is also the possibility your fuel pump regulator is shot. check the fuel pressure with the engine off and see how high it goes. You should also be taking the pressure with the vacuum line disconnected from the regulator.
 

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Discussion Starter #6
The bronco gets driven offroad a lot. Two or three times a week for the past couple of months.
When I get home I will check the fuel pressure again using the method jopes suggested.
 

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Ok, just a shot in the dark. This same thing happened to me but it wasn't a fuel issue. There was moisture under my distributor cap from soaking it a few too many times with water.. The problem you are having sounds more like a fuel issue, just figured I'd offer what I had.
 

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Discussion Starter #8
I checked the fuel pressure with the vacuum line disconnected and the truck at idle and now it only reads 19psi. Vacuum line reconnected made no difference, it stayed at 19psi. With the truck off it only read 9psi. What else can I check to figure this out?
What is the "purge canister failure" code and is it related to the fuel issue?
 

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one of 2 things, your pump is either dead or your regulator is dead, I would probably at this point put money on your regulator failing. it should be easier to change than dropping the tank to swap pumps again.
 

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I checked the fuel pressure with the vacuum line disconnected and the truck at idle and now it only reads 19psi. Vacuum line reconnected made no difference, it stayed at 19psi. With the truck off it only read 9psi. What else can I check to figure this out?
What is the "purge canister failure" code and is it related to the fuel issue?
purge canister code is strictly emissions shouldnt cause driveablilty concerns
 

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Discussion Starter #11
Thanks for the help guys.
The regulator was faulty or clogged. Not the easiest three bolts to reach but, not the worst either. I owe you a beer jopes.
 
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