1994 Mazda Protege Fuel Pump Shuts Off

1994 MAZDA
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BBARNHILL
  • MEMBER
  • 1 POST
I just did a motor swap on this car and now the fuel pump will not stay on. It comes on when cranking the engine and it starts fine but as soon as you release the starter and go back to the ign. position the fuel pump shuts off, and the motor dies as soon as the fuel pressure drops to 20 lbs. I assume that there is some sort of feedback from the motor to the computer to tell it the motor is running and for the fuel pump to stay on. I checked all the connections and can't find anything disconnected. I need to know where the fuel pump relay is and what might be causing it not to stay on. I have no wiring diagram so I'm really at a disadvantage. This might be a duplicate message since on the previous one I went up to donate before I submitted my guestion and couldnt get back to my original posting. I would sincerly appreciate a prompt reply so I can get this rig out of my garage, my wifes car needs some desprate attention and I can't do anything untill this car is out of here. Thanks Bill B.
Dec 25, 2006 at 4:42 AM
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2CARPRO JACK
  • ✓Experienced Mechanic
  • 11,533 POSTS
That car doesnt have a fuel pump relay. The PCM turns on the fuel pump on siganl from the ignition switch and ignition coil. Be sure all grounds are hooked up and have good connections.If you used the coil off the new engine , swap it out with the old one or any parts that werent on the original engine.
Dec 26, 2006 at 1:48 AM
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Suggested Repair

This model has no fuel pump relay; the PCM keeps the pump on using signals from the ignition switch and ignition coil. Verify all grounds are connected and clean. If the coil or other parts came from the replacement engine, reinstall the original coil or original engine parts.

Conversation Summary

After an engine swap on a 1994 Mazda Protege, the fuel pump runs and the engine starts while cranking, but the pump shuts off and the engine dies when the key returns to the ignition position as fuel pressure falls. The owner could not find a disconnected connector and asked about the fuel pump relay. The expert said there is no fuel pump relay and that the PCM controls the pump from the ignition switch and ignition coil. They advised checking all grounds and swapping back the original ignition coil or any parts not from the original engine.

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