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Fuel Pump Problems?Ask Bob

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[The Number One Problem Is When You Do Everything Right,But Charge The Fuel Pump With 12Volts]
If you have checked the bulb, wiring and connections, and still have no "ses" lamp, the ecm is at fault. But be sure to thoroughly check all the wiring and terminals, before you replace the ecm.

No ALDL data, won't flash code 12, light on steady: This is usually caused by a shorted (brn/wht) wire to ground, or a open wire in the ALDL terminal "A" to ecm pin A9, when the terminals "A" and "B" are connected for a diagnostic check. First try unplugging the A-B ecm connector, if the light goes off, then the brn/wht wire is not shorted to ground, and the wht/blk wire from the ALDL to ecm is not opened. Check all terminal connectors. If they check out, the problem is a faulty memcal, or ecm. If a code did not flash, the ecm should be replace using the original memcal. Replace the memcal only if a ecm swap did not correct the problem.

Engine cranks but won't run: Be sure the battery voltage is sufficient (around 12.5 volts + or - .5V or so), the starter cranking speed is sufficient to turn the engine over with no hesitation, and their is fuel in the tank. Jumper the ALDL terminals "A" and "B", with ignition switch on, but engine not running, see if you have code 54. If you do, check the wiring to the fuel pump relay. Pull your ALDL jumper, turn the ignition key off for about 15 seconds, then to "on" position again. You should hear the fuel pump run for about two seconds, and then stop. If this does not happen, locate the fuel pump test terminal "G" on the ALDL, connect a jumper from a hot wire source, and connect to this terminal. The fuel pump should run. If it does, the fault is in the relay, or the ecm. If the pump does not run, check the connection of the fuel pump by the fuel tank for a loose or corroded connection. Circuit below is what is typical with a 1985-89 tpi harness with maf sensor.
Testing for Engine Trouble Codes
With the ignition "off", insert a jumper wire between the A & B terminals. Turn the ignition to the "run" position but do not start the car. The check engine light will start a sequence of blinks.
For example: 1 flash, pause, 2 flashes
This sequence would denote code 12 which should be present every time you test for codes. Any stored trouble codes will follow code 12.
View the ECM Trouble Codes link in the Tech section for a full list of codes and their possible causes.

Test the Automatic TCC Circuit
Terminal F is used to test the TCC circuit in the automatic transmission.

Fuel Pump Test
Terminal G is used to test the operation of the fuel pump without removing the tank or unplugging the relay.
Apply 12 volts directly to terminal G and the fuel pump should run. This makes it easier to see if a pump is functional and provides the correct amount of fuel pressure. This can also be helpful when trying to drain old fuel. You can disconnect the fuel feed line, run it into a suitable container and activate the pump in order to completely drain the tank & lines.

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