Still having fuel pressure issues

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Mar 30, 2007 | 12:33 AM

nickpierce

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Still having fuel pressure issues

My 89 f150 will start and run fine, then act like its running out of gas and barely run to make it home. I replaced the high pressure pump, no help. The fuel pressure guage says pressure is right on, but then while idling it lost pressure and died, so i know fuel pressure is a problem. Im thinking in tank pump? BTW, it has dual talks and for the last few months its been filling the wrong tank with the return fuel.

Mar 30, 2007 | 12:39 AM

jakesdad36

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Does it do it on either tank? The in tank pumps are just low pressure siphon pumps. You have changed the fuel filters right?

Mar 30, 2007 | 12:40 AM

nickpierce

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Its done it to me on both tanks, yet i will say the back tank could be about out of gas....i replace the in line filter that is in front of the hp pump

Mar 30, 2007 | 12:45 AM

jakesdad36

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Yes it is just in front of the hi pressure fuel pump just as the frame rail starts to curve up.

Mar 30, 2007 | 12:49 AM

nickpierce

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replaced it

Jul 7, 2007 | 11:46 PM

azbronco96

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sounds like the fuel delivery pressure switch is bad. it's down by high pressure pump when they go bad it allowes the gas to go 2the tank that not being used.

Jul 8, 2007 | 06:52 AM

subford

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From: Easton,Ks

Quote:

Originally Posted by azbronco96

sounds like the fuel delivery pressure switch is bad. it's down by high pressure pump when they go bad it allowes the gas to go 2the tank that not being used.

There is no such thing in the fuel system.
A bad fuel selector valve will let the return fuel go to the front tank if running on the back tank. It does switch tanks from the pressure from the boost pumps in each tank.
Is this what you are talking about?
Here is a diagram of your fuel system.

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Jul 8, 2007 | 07:14 AM

subford

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From: Easton,Ks

Quote:

Originally Posted by nickpierce

Look at the wires under the fuel pump relay and its socket.
If all looks good ground pin #6 of the DLC (test connector) and watch the fuel pressure and see if it holds.
If it does start the truck and watch the fuel pressure.
If it holds fuel pressure and dies then it is in the ignition system and more than likely the TFI module.
Your fuel pressure should be 34-35 at idle and about 43 PSI with WOT or the vacuum hoes off the fuel pressure regulator for a 5.0, 5.8 or 7.5.
A 4.9 has higher fuel pressures into the 50's.

You also have a bad Fuel selector valve on the frame but I do not think it is causing the fuel pressure problem with its stuck "O" ring putting the gas in the front tank while running on the rear tank. It never fails the other way around on filing the wrong tank.