bad fuel pump?
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Junior User
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bad fuel pump?
I have a 96 explorer with a 4.0 V6. I have noticed a drop in fuel milage (from 19+ to 17) and when the fuel level gets below 3/8 tank, the engine will idle rough. It will intermittently idle rough other times also but always below 3/8 tank. I changed the fuel filter and checked the fuel pressure and it was 30 psi. I thought that normal pressure is somewhere around 80 psi. any help would greatly appreciated
Cargo Master
Joined: Aug 2003
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From: BC Canada
If the pressure stays at about 30-35psi (regulated) you are ok.
If it drops below, then you may have a restriction or weak pump, if the pressure goes up substantialy you have a problem FPR.
Did you take the reading at the rail with the engine running??
Have you checked the venting system on the fuel circuit??
Do you have any codes??
If it drops below, then you may have a restriction or weak pump, if the pressure goes up substantialy you have a problem FPR.
Did you take the reading at the rail with the engine running??
Have you checked the venting system on the fuel circuit??
Do you have any codes??
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I took the pressure reading at the fuel rail. There are no restrictions in the return line and there are no codes.I just cleaned the MAF sensor again to see if it makes any difference but, without any codes, I am just trying to go through everything I can think of to fix the problem......
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It's obvious that the fuel pump doesn't know how much fuel is in the tank. All I am doing is giving symptoms and when they occur. The rough idle below 1/2 tank has happened the last 6 times or so. Every time it occurs, when I fill the tank, the rough idle disappears. I have run injector cleaner through twice with no positive results. Without and codes, it is very difficult to troubleshoot as to what is malfunctioning and causing the poor fuel milage and rough idle. I was hoping that somebody has run into this before and could point me in some direction to proceed. As to doing all of the basics, I have changed plugs, wires, thermostat, checked fuel pressure, replaced fuel filter, and checked for vacuum leaks.
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I was thinking of pulling the EGR cleaning and checking for proper operation. About 8 months ago I changed the EGR back pressure valve because of a code but the problems that I am presently having started a few months after I changed it so I didn't think they were related.
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