95 f250 5.8 4x4

Replaced fuel pump, fuel pressure regulator, filter and still when it gets hot it runs on 2 cyclinders, backfiring through the intake.

After fuel pump was replaced (no fun) the pressure was about 32 psi and drove about 50 miles, all good, then back to barely making it home, fuel pressure 20 psi..

Any ideas, have blown air through the lines and disconnected the filter and when pump was turned on it flowed.


Any kind of relay that could go bad when hot?
God Bless
John

 

Check your voltage at the pump with the pump running.

 

You should pull any stored codes

 

Should it be 12 volts.?? Also, the bed is back on so I guess I can check at the connector, right?

 

Yes, just probe the wire....it should be the same as any other wire that carries voltage, with engine running. Yes it would be 12 + volts. Do you have single or dual tanks?

 

Thanks so very much for your help.

Have dual tanks but the front has been removed by PO.

I get 7.5 volts at connector to fuel pump with "key on' engine off. Would it be different if it were running. To check with engine running where do and how do I check it??

 

Engine needs to be running. Just probe the wire with the sharp point of a multimeter and read voltage. Or have some one turn the key to run while you are checking for voltage. The CPU only sends a signal for few seconds to prime the pump and then it kicks off until you turn the key to start. That is why you hear that brief whine before you start turning the key to start.

 

Got 12v at the pump side of the connector wheh running (12 volts on one wire).

I guess either my computer is bad or the new pump is bad . Would the computer cause the pump to produce low psi??

 

No, the computer tells the pump to turn on or off. It does not control the fuel pressure.

 

I replaced the FPR with a junk yard unit, guess it could be bad. When I disconnect the vacuum there is no change. I have a trailer I had to store at a business yesterday due this problem and really in a bind. Any help much appreciated.

Do Fuel Pressure regulators work good and bad or it's works or doesn't??

God Bless John

 

Follow the black wire back from the connector to where it terminates on the frame and make sure its a good clean and tight connection. On my 94 a bad ground caused my connector to the fuel pump become resistive.
regards
rikard

 

Do u mean the connector at the tank and I assume this is the ground correct? Where does it normally terminate on the frame. FYI when I wiggled the connector wires and the idle would change sometimes.(smooth out).

Thanks

Will do it within 30 min and let u know.

John

 

Conanski was right, even though the fuel pump was only 3 months or less old, I removed the bed (again) checked pressure at the pump itself, still 20 psi.

Replaced pump and got 30 at idle engine off and running, WOT 40, vacuum line off fpr jumps about 8 psi.

Now if I replace the leaking brake booster I am assuming the pressure will go up, or am I mistaken?

God Bless
John

 

You are mistaken.

 

Yep, I guess it would be the other waY!