EFI Fuel Pump Question, Fuel pump doesn't run Options

[chris914]

When I turn the ignition on the pump doesn't run. It's a stock 74 2.0L.

Are the two wires connected to the pump +/- 12 volts?

I used a multimeter and there doesn't seem to be any voltage going to the pump.

Is there a relay that supplies voltage or does it come from the ignition switch.

I did check the fuses and made sure they were seated.

Thanks!

[Mike Bellis]

The stock 914 FI does not have a priming cycle like modern EFI. The trigger points in the dizzy tell the ECU to turn on the pump and fire injectors.

[chris914]

The stock 914 FI does not have a priming cycle like modern EFI. The trigger points in the dizzy tell the ECU to turn on the pump and fire injectors.

Do you have any suggestion on trouble shooting that? In other words what would you do to fix that. lol

[Tom]

The fuel pump gets it's power thru the fuel pump relay on the relay board. The relay closes by the ECU providing a ground and powers the fuel pump when three conditions happen.
1- initial key switch to ON,
2- when the starter is cranking,
3- when engine RPM's exceed XXX RPM's
See picture for location of fuel pump relay.
Tom

[ClayPerrine]

On a D-Jet car, the fuel pump will run for 2 seconds to prime the fuel ring when the key is turned on.

Troubleshooting procedure:

Get a 12V test light from FLAPS.

Hook the alligator clip on the test light to a good ground. In the engine compartment, use the battery negative post. I like to make a really long wire with a loop connector bolted to the battery negative post so I can go anywhere in the car for testing purposes. Verify you have a good test light by touching the probe to the battery positive. I learned the hard way one time to always verify the test equipment.

Go to the relay board.

Remove relay 75.

Using a test light, check to see if there is power at pin #30.

If there is no power, check for power on both sides of the rear most fuse (#91) on the relay board. It should have power on both sides. If it only has power on the right side, then you have a problem with the fuse, and you will need to remove the fuse, clean and tighten the relay board fuse contacts, and replace the fuse with a new 25 amp fuse. If the fuse is blown, and it blows again when you replace it, find the Auxiliary Air Regulator. It is on the intake plenum, on the left front side. Disconnect the white wire from it and see if the fuse blows again. If it does, then the white wire between the relay board and the Auxiliary Air Regulator is shorting to ground. I would remove the cover off the 12 pin connector at the back of the relay board and take the white wire out of it. This will disconnect the Auxiliary Air Regulator circuit. That will prevent the car from idling up when cold, so you will have to hold the throttle manually until it warms up. If the fuse does not blow with the white wire disconnected from the Auxiliary Air regulator, then the Auxiliary Air Regulator is shorted internally. You will need to source a replacement. They are NLA, so you will have to find a used one, or replace it with the L-Jet one. The L-Jet one is a different design, but performs the exact same function. You will have to add a L-Jet injector plug to connect it and you will have to ground the second lead.

If you do have power on pin #30, then use a jumper wire to connect pin #30 to pin #87. You should hear the fuel pump run.

If you do not hear the fuel pump run, leave the jumper in, and go to the pump and unplug it. Using your test light, see if one of the contacts on the fuel pump plug has power.

If you don't have power, you have an open circuit between the relay board and the fuel pump. Remove the cover off the 14 pin connector and check pin 13 (the one on the left end of the front row) with the test light. If you don't have power there, then you have a bad relay board. If you do, then you have a broken wire between the fuel pump and the relay board. The wire color is black with a yellow tracer.

If you do have power at the fuel pump, then check the ground at the pump. Move your alligator clip on the test light (or your extension wire) to the positive side of the battery. Test the other side of the fuel pump plug. If the light does not come on, then you have a bad ground. If the fuel pump is in the original rear location, it grounds at the post above the relay board. If it is a 75 or 76, where they moved the pump up front, then it grounds at the ground lug above the fuse box inside the car.

If you have a good ground, then you have a failed pump. A replacement can be obtained from FLAPS. Ask for Airtex E8445. This pump will be the correct pressure and volume, but will only have 2 fittings. If you have a 3 fitting pump, just remove the Y fitting in the line and hook the two return lines together.

Let us know the results of testing.

[JawjaPorsche]

On a D-Jet car, the fuel pump will run for 2 seconds to prime the fuel ring when the key is turned on.

Troubleshooting procedure:

Get a 12V test light from FLAPS.

Hook the alligator clip on the test light to a good ground. In the engine compartment, use the battery negative post. I like to make a really long wire with a loop connector bolted to the battery negative post so I can go anywhere in the car for testing purposes. Verify you have a good test light by touching the probe to the battery positive. I learned the hard way one time to always verify the test equipment.

Go to the relay board.

Remove relay 75.

Using a test light, check to see if there is power at pin #30.

If there is no power, check for power on both sides of the rear most fuse (#91) on the relay board. It should have power on both sides. If it only has power on the right side, then you have a problem with the fuse, and you will need to remove the fuse, clean and tighten the relay board fuse contacts, and replace the fuse with a new 25 amp fuse. If the fuse is blown, and it blows again when you replace it, find the Auxiliary Air Regulator. It is on the intake plenum, on the left front side. Disconnect the white wire from it and see if the fuse blows again. If it does, then the white wire between the relay board and the Auxiliary Air Regulator is shorting to ground. I would remove the cover off the 12 pin connector at the back of the relay board and take the white wire out of it. This will disconnect the Auxiliary Air Regulator circuit. That will prevent the car from idling up when cold, so you will have to hold the throttle manually until it warms up. If the fuse does not blow with the white wire disconnected from the Auxiliary Air regulator, then the Auxiliary Air Regulator is shorted internally. You will need to source a replacement. They are NLA, so you will have to find a used one, or replace it with the L-Jet one. The L-Jet one is a different design, but performs the exact same function. You will have to add a L-Jet injector plug to connect it and you will have to ground the second lead.

If you do have power on pin #30, then use a jumper wire to connect pin #30 to pin #87. You should hear the fuel pump run.

If you do not hear the fuel pump run, leave the jumper in, and go to the pump and unplug it. Using your test light, see if one of the contacts on the fuel pump plug has power.

If you don't have power, you have an open circuit between the relay board and the fuel pump. Remove the cover off the 14 pin connector and check pin 13 (the one on the left end of the front row) with the test light. If you don't have power there, then you have a bad relay board. If you do, then you have a broken wire between the fuel pump and the relay board. The wire color is black with a yellow tracer.

If you do have power at the fuel pump, then check the ground at the pump. Move your alligator clip on the test light (or your extension wire) to the positive side of the battery. Test the other side of the fuel pump plug. If the light does not come on, then you have a bad ground. If the fuel pump is in the original rear location, it grounds at the post above the relay board. If it is a 75 or 76, where they moved the pump up front, then it grounds at the ground lug above the fuse box inside the car.

If you have a good ground, then you have a failed pump. A replacement can be obtained from FLAPS. Ask for Airtex E8445. This pump will be the correct pressure and volume, but will only have 2 fittings. If you have a 3 fitting pump, just remove the Y fitting in the line and hook the two return lines together.

Let us know the results of testing.

Awesome easy to understand troubleshooting! (IMG:style_emoticons/default/beerchug.gif)

[MikeM]

What a great response from Clay Perrine....

[Cap'n Krusty]

The stock 914 FI does not have a priming cycle like modern EFI. The trigger points in the dizzy tell the ECU to turn on the pump and fire injectors.

Well that's just flat out wrong in every way ................................................

The Cap'n

[Dave_Darling]

Not quite every way... The trigger points do provide the RPM signal to the ECU, and the ECU will run the pump if it detects RPM above a certain point. (50 RPM? I forget!)

But yeah, D-jet does provide a "priming cycle".

--DD

[sixnotfour]

The pumps usually either work or they don't. The pump runs whenever the ignition switch is in the on or start position and the engine is turning. The AFM has a microswitch which is activated as soon as the AFM's door moves. This microswitch allows the fuel pump to run. This is a feature designed to prevent flooding and for safety. The idea here is that if the engine is not running then the AFM door will be closed and the fuel pump will not run regardless of ignition switch position.

[Tom]

sixnotfour.
That is only true for L-Jet.
Tom