Rick's Free Auto Repair Advice

Ford F150 won’t start

Diagnose and fix Ford F150 won’t start condition

Some shops are reporting a Ford F150 won’t start condition where testing shows no injector pulse and no fuel pressure. Here are the steps to take if you run into that situation. The problem seems to happen more often on 2009-10 Ford F150 with the 4.6L and 5.4 engine

Check for power at fuel injectors

Power is supplied to all fuel injectors on the blue wire. Turn the IGN to run and check

no start, no power at Fuel Injector

Fuel Injector

for battery voltage on any of the blue wires at any injector. If you don’t see battery voltage, go on to the next step.

Check for a blown fuse

The fuse that powers the fuel injectors and fuel pump driver module is fuse #27, located in the battery junction box. If the fuse is good, move on to the next step. If not, replace the fuse

Swap the fuel pump relay

If the fuse is good, find another rely in the junction box with the same id number and size and AC compressor relayswap it with the fuel pump relay. Then repeat the voltage check to the injectors on the blue wire. If that works, buy a new relay and call it a day.

Bypass the fuel pump relay

If the fuse is good and swapping the relay didn’t help, it’s time to dig in deeper. Remove the fuel pump relay and jumper across terminals 3 and 5. Those are the two larger terminals in the relay socket. Then check for fuel injector and fuel pump operation. If it’s still a no go, then you’ve got a wiring harness issue

To diagnose the wiring harness

You want to locate and repair any high resistance or open condition in this circuit that provides power to the injectors and fuel pump. The fuel pump circuit wires leaving the junction box are violet and green. Then they splice into blue wires for the fuel injectors. Locate the high resistance or open and repair it.

©, 2017 Rick Muscoplat

Posted on by Rick Muscoplat

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