Question about Ford F-150

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1996 F150 Ford truck 5.0 Starts and dies. Fuel pressure is 30 to 35psi . has good spark Has code for MAF but new MAF did not help. Has O2 codes shorted or open ? Ideas?

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  • cjkas Oct 13, 2010

    this truck has dual tanks filter is new . i re-checked my pressure . 38psi key on engine off. 30psi when i attempt to start it. All Data specs show me 35 -45 psi key on engine off 30to 40 running? It reads the same on both tanks

  • cjkas Oct 15, 2010

    trouble codes PO135 and PO 155 O2 Heater circuit ? Key on engine off pressure is 38psi and steady



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You should have constant fuel pressure when the engine is off and the fuel pump pressureized as well as with the engine running. What trouble codes were pulled from the PCM? Were they O2 codes?

Posted on Oct 14, 2010

  • GetMeOttaHere Oct 15, 2010

    Both codes are related to the O2 heater circuits. The upstream and downstream O2 sensors have a defective heat circuit and may even be stuck in a rich or lean condition.


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30-35 PSI is NOT enough fuel pressure, u should have 42-44 PSI minimum, in the shop 44 PSI at idle is about average, and about 50 PSI when you throttle the engine quickly, it should never go down, I suspect u have lean codes showing on the O2, also check for a plugged fuel filter, the filter is under the truck inside the frame rail below the drivers seat area.

Posted on Oct 13, 2010


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