bad fuel pump???
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Mountain Pass
Joined: Sep 2003
Posts: 188
Likes: 1
From: Michigan
bad fuel pump???
how do i know if my rear fuel pump is going bad?? the truck is running, but when i use the rear tank it runs ruff and then clears up and then its hit and miss it runs good and runs bad some times i give it gas and it hesitates and then its fine... could i have the little black hoses hooked up wrong?? the ones that go on the fuel pump???? any help would be great
Last edited by remmers; Nov 20, 2003 at 08:40 PM.
Senior User
Joined: Sep 2002
Posts: 167
Likes: 0
From: Alberta
You should use a fuel pressure gauge to check the pressure getting to the fuel rail. I think its should be aroud 35 to 40 psi? (someone else here should be able to give you a proper range). I don't believe the truck would run at all if you had the supply and return lines crossed (I'm not even sure you could; on my truck I seem to remember that the lines were slightly different sizes, and push-on connectors wouldn't fit? Not quite sure about that). Having said that, if the front tank works fine, but the rear tank causes intermittent problems, my money's on your rear pump starting to go out. My front fuel pump acted the same way; I could go for weeks on the front tank without any problems, yet every once in a while it would cause my truck to buck and stall (usually either on the highway or in the middle of an intersection). I changed it out about 8 months ago, and haven't had any problems with it since.
Senior User
Joined: Jun 2003
Posts: 176
Likes: 0
From: Massachusetts
I would check to see if your truck has a recall on the fuel pressure regulator. I had mine relaced last year on a recall. It's a 93 F150. Worth looking into since I think it could cause the probelm you are describing.
Posting Guru
Joined: Dec 2002
Posts: 1,297
Likes: 3
From: Billings MT
I have had the same problem. It is theoretically possible that the fuel pump is heating up and internally bypassing. Those familiar with hydraulic pumps will understand, since the fuel pump is just a specific hydraulic pump.
If you switch tanks, does it do the same thing? If not, I doubt that it is your pressure regulator. As I recall, there is only one at the fuel rails.
It could be junk in the tank that gets sucked up to the screen and restricts flow into the pump. If I switch tanks for about 10 miles, and go back to the rear tank, it's fine.
Personally, I have never had an electric fuel pump show signs of failure, besides just failing.
Check out HERE and it might give you specific fuel pressures. I am not certain though.
If you switch tanks, does it do the same thing? If not, I doubt that it is your pressure regulator. As I recall, there is only one at the fuel rails.
It could be junk in the tank that gets sucked up to the screen and restricts flow into the pump. If I switch tanks for about 10 miles, and go back to the rear tank, it's fine.
Personally, I have never had an electric fuel pump show signs of failure, besides just failing.
Check out HERE and it might give you specific fuel pressures. I am not certain though.
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
The 7.5L engines are notorious for having fuel pump problems - do a search and read thru some of the threads.
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Senior User
Joined: Nov 2003
Posts: 219
Likes: 0
From: chino valley az
7.5 fi should have 32-42 psi with vacuum hose connected and at least 7 psi more with it disconnected.. Kurt
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