sub_dont_touch Posted July 8, 2009 Share Posted July 8, 2009 (edited) Hi, I removed my fuel pump assembly from my 1994 EJ18 Impreza. It looks in good condition to me, but who am I to tell. I want to know if there is any way to tell if it needs to be replaced or cleaned? And how would I clean it? I also checked for power at the fuel pump itself with the connector plug in. There was 0.01v at the pump. but 11v at the connector plug. this is no damage to the plug or wires at all. Edited July 8, 2009 by sub_dont_touch Quote Link to comment Share on other sites More sharing options...
Cougar Posted July 9, 2009 Share Posted July 9, 2009 To check the pump motor operation just connect it to directly to the battery or a 12 volt DC power source that can handle around 8 amps of current. The differences in the voltage you saw may be due to the way the circuit is designed and the way you measured it. If you measured the voltage with the reference probe of the meter tied to ground then there is a connection problem at the connector. If you measured the voltage across the pump then the ground for the pump may be controlled by the ECU and if the pump wasn't running there would be no voltage drop across the motor, it would all be across the open ground connection. Quote Link to comment Share on other sites More sharing options...
sub_dont_touch Posted July 9, 2009 Author Share Posted July 9, 2009 checked the pump with my car battery. sounds like its working. I think I know what you mean. I just probed the black wire with the black probe and the red with red probe. gave 0.01v and sometimes nothing. how should I be checking it at the pump? Quote Link to comment Share on other sites More sharing options...
nipper Posted July 10, 2009 Share Posted July 10, 2009 You need to put the pump back in and use a pressure gauge. What was the initial prblm that got you to the fuel pump? nipper Quote Link to comment Share on other sites More sharing options...
Cougar Posted July 11, 2009 Share Posted July 11, 2009 checked the pump with my car battery. sounds like its working. I think I know what you mean. I just probed the black wire with the black probe and the red with red probe. gave 0.01v and sometimes nothing. how should I be checking it at the pump? To see if voltage is getting to the pump motor place the black meter probe to a good chassis ground point and the red probe on the wire connection to the pump and with the pump reconnected. If you have 12 volts on the wire then the ground to the pump motor is either open or the switching action in the ECU for the ground isn't working. Quote Link to comment Share on other sites More sharing options...
sub_dont_touch Posted July 20, 2009 Author Share Posted July 20, 2009 To see if voltage is getting to the pump motor place the black meter probe to a good chassis ground point and the red probe on the wire connection to the pump and with the pump reconnected. If you have 12 volts on the wire then the ground to the pump motor is either open or the switching action in the ECU for the ground isn't working. At the pump this is no power or 0.01v At the pump side of the connector plug there is 9v with the red on the plug and black on the chassis. AND 12v when red and black on the plug. Other side of the connector plug is 12v for both. Quote Link to comment Share on other sites More sharing options...
Gloyale Posted July 20, 2009 Share Posted July 20, 2009 Bad wire from pump connector to pump. Unscrew the wires, solder a new wire up using the old connector ends, and reassemble. But hmmm.....if you are running the pump by powering the connector end of the wires, then the wire must be good....idk...you're on the right track for sure. Quote Link to comment Share on other sites More sharing options...
sub_dont_touch Posted July 20, 2009 Author Share Posted July 20, 2009 (edited) The wires and connections are all ok. It's weird because it can only be the ECU now really. Or the fuel pump itself but I doubt it. Have checked the wiring and have swapped the fuel relay with a relay that was next to it on the same bracket. How do I run power straight to the fuel pump so it's running all the time? I know it's dangerous to drive around on. BUT this would tell me if I need a new fuel pump or not, am I right? Something about bypassing the relay or something? Edited July 20, 2009 by sub_dont_touch Quote Link to comment Share on other sites More sharing options...
Gloyale Posted July 20, 2009 Share Posted July 20, 2009 The wires and connections are all ok. It's weird because it can only be the ECU now really. Or the fuel pump itself but I doubt it. Have checked the wiring and have swapped the fuel relay with a relay that was next to it on the same bracket. You said that there is 12v to the pump connector. You mean the one back at the tank? If you are getting voltage there, the relay is not the problem. Quote Link to comment Share on other sites More sharing options...
sub_dont_touch Posted July 20, 2009 Author Share Posted July 20, 2009 Yes 12v at the tank connector plug. But only 9v on the other side of the plug closest to the pump itself. And 0v at the pump itself. Quote Link to comment Share on other sites More sharing options...
Cougar Posted July 21, 2009 Share Posted July 21, 2009 The drop down in voltage from 12 volts to 9 means there is a connection problem there. It would also appear there is another bad connection between where you measured the 9 volts and 0 volts, unless you measured the ground lead somehow. That would be 0 volts. Quote Link to comment Share on other sites More sharing options...
sub_dont_touch Posted July 24, 2009 Author Share Posted July 24, 2009 Went and got a spare fuel pump housing, swapped over the gas tank gauge meter thing. Before putting my fuel pump on, checked for power and there was 12v! So with my hopes up, put the fuel pump on, put the assembly back in the tank, tried starting my car but still not starting. To me this must mean that the fuel pump is bad? Quote Link to comment Share on other sites More sharing options...
Gloyale Posted July 24, 2009 Share Posted July 24, 2009 Yes 12v at the tank connector plug. But only 9v on the other side of the plug closest to the pump itself. And 0v at the pump itself. Replace the connector and in tank wiring. Or probably easier to get the whole unit used from a wreck. That, or I'll bet Subaru has a part# for just that wiring connector bit, you could order. Quote Link to comment Share on other sites More sharing options...
sub_dont_touch Posted July 24, 2009 Author Share Posted July 24, 2009 Replace the connector and in tank wiring. Or probably easier to get the whole unit used from a wreck. That, or I'll bet Subaru has a part# for just that wiring connector bit, you could order. I've replaced the connector, 12v. Fixed that problem then. BUT not getting fuel still so it has to be the fuel pump, can't be the relay if there was 12v everywhere along the connections. Could it still possibly be the ECU? how do I test the grounding? Quote Link to comment Share on other sites More sharing options...
Olnick Posted July 24, 2009 Share Posted July 24, 2009 BUT not getting fuel still By that do you mean the pump is still not running? Quote Link to comment Share on other sites More sharing options...
sub_dont_touch Posted July 24, 2009 Author Share Posted July 24, 2009 well theres power to it. the car is still not starting. So yes. Quote Link to comment Share on other sites More sharing options...
Olnick Posted July 24, 2009 Share Posted July 24, 2009 well theres power to it. If there is power to the pump do you hear it running? Quote Link to comment Share on other sites More sharing options...
Cougar Posted July 24, 2009 Share Posted July 24, 2009 I think your pump is tied to ground directly and if so then the pump should run if it is good and you have 12 volts getting to it. Check the voltage across the leads of the pump directly. If you still have 12 volts there and the pump isn't running then it is bad. If the ground of the pump is controlled by the ECU then you may be getting confused with the power running to the pump. An open ground lead will have voltage on both sides of the pump leads when the common meter lead is connected to ground. Quote Link to comment Share on other sites More sharing options...
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