fuel delivery issues

Trouble shooting Fuel pump FPDM issues 99-04 MY

The AFM link is an example of what happens when the Ford test procedures are picked up in mid stream without all of the proceeding tests being performed in the correct order. If you read the entire thread, the poster was sure that each new FPDM quickly burned out because replacing the part did not resolve the original problem and the final test still showed voltage to the FPDM. IMO, likely the poster replaced several good FPDM modules. A very expensive mistake.

Since power has been confirmed at the trunk IFS switch, we can skip those tests. And yes the P1237 very well could result from cranking with the IFS tripped or disconnected.

There is an electrical connection accessed in the center of the bumper from below by the gas tank. It is round. On the 99-04 MY it is connector C463. Split the connector and from the car side, test the RD/BK pin#7 and BN/PK pin#6 for 12 volts. It will be necessary to pulse the ignition key because the Fuel Pump will prime for only 3 seconds. Be careful that you do not short out any of the other pins as this could be a costly mistake. If you see voltage, this indicates a good functional test of everything but the fuel pump itself.

Next use a battery charger to inject +12 volt towards the fuel tank to the RD/BK pin#7 (+) and BN/PK pin#6 (-). This will force the fuel pump to run. Make note of the amps. A paper clip will help probe the connector. It may be wise to wrap the clamps with electrical tape just to prevent sparks.

The draw should be around 5-7 amps if my memory serves me. If the draw is very high, suspect a locked fuel pump rotor or other internal short. Also remember that when the car is not running, in a return-less system the fuel pump is working against a blocked head. It would be expected if allowed to run, the amps would rise as the fuel pressure also climbed.

If you do not hear the fuel pump run, based on the other tests, this confirms a diagnosis of a bad fuel pump.

If the Fuel pump does run, and no power from the FPDM, this points very strongly at a bad FPDM.

Disclaimer, the above tests do not conclusively rule out a bad PCM. Nor do they rule out a wiring problem from the FPDM to PCM or FPDM to fuel pump.

Disclaimer2, testing the fuel pump by forcing it to run is a basic functional test. This does not confirm that the fuel pump is capable of providing the correct amount of fuel while running. There is a possibility that the electrical motor could be fine but an internal failure of the pump itself results in the pump not generating enough fuel pressure. Such a condition could be caused by a blocked fuel pump pick up.

For whatever cost cutting reasons, Ford dropped the fuel line Schrader valve in later MY Mustangs. This removed an easy test port to confirm fuel pressure. Ford does make a special adapter that inserts between the fuel line and the fuel rail to add a Schrader valve for testing.

Another option to verify fuel pressure is by monitoring the fuel pressure PID with an ODB2 scanner.

Also, remember the "force fuel pump to run" procedure. It may prove handy to drain the tank (assuming it runs at all). Simply disconnect the fuel filter and with a spare piece of vacuum line, direct the flow into a suitable container. If the fuel pump is complete toast, then there are very limited options to drain the tank because the anti-rollover check value in the filler neck makes siphoning very difficult. Ford does make a special tool to hold the check valve open and direct a hose into the tank without damaging the check valve. However, this is not really practical for the home mechanic.

Hissin I thought you knew everything there was to know about cars. I guess your not the car god I thought you were lol.


Get it figured out?