TPain Posted January 29, 2012 Share Posted January 29, 2012 (edited) I posted earlier about an electrical problem. My battery died after the dome light was left on. I went to jump it and blew a fusible link; I did not cross the wires and I have no idea what happened. I replaced the fusible link but still, the car would not start. I learned that the issue was related to the fuel pump. The fuel pump is getting power but it's not getting a ground signal, the ground signal comes via the ECM. We swapped out the ECM to see if something was wrong with it. After the swap, still no ground signal. My ECM appears to be fine. It's got to be something coming into/not coming into the ECM. What else could it be? All the fusible links are good, all the fuses are good. Thinking it's a grounding issue but none of the Subaru manuals, Haynes or Chilton list all the locations of grounding point up to the ECM. To make matters worse, I have to hold my mechanics hand all through this process and I've lost all confidence in him. After all, I originally took my car into him for an axle problem. Help, anyone? I could really use. Thanks. Edited January 29, 2012 by TPain Quote Link to comment Share on other sites More sharing options...
naru Posted January 29, 2012 Share Posted January 29, 2012 Are you sure the fuel pump grounds thru the ECU? My not completely trustworthy 85 diagram indicates it does not. I know later models do. Have an 85-86 FSM to look at? Quote Link to comment Share on other sites More sharing options...
TPain Posted January 29, 2012 Author Share Posted January 29, 2012 Yes. I have been talking with General Disorder, straightened a ton of stuff out. Unfortunately, my mechanic Jeff hit the wall. He didn't how to fix the car. Quote Link to comment Share on other sites More sharing options...
naru Posted January 29, 2012 Share Posted January 29, 2012 (edited) OK Got spark?Tach move? Pump will only run for a couple seconds if the ECU doesn`t see ignition pulses. Ignition pulse signal wire hooked to coil - ? It is a grey shielded wire on my 84. Got continuity between between the ECU plug and fuel pump ground? Between coil - and the ECU plug ignition pulse wire? Not totally unheard of for the ECU fuel pump driver to fail.Mine did. 2 in a row seems unlikely though. As a last resort,I would check resistance between the ECU grounds and battery negative. Edited January 29, 2012 by naru last resort Quote Link to comment Share on other sites More sharing options...
naru Posted January 29, 2012 Share Posted January 29, 2012 OK Got spark?Tach move? Pump will only run for a couple seconds if the ECU doesn`t see ignition pulses. Ignition pulse signal wire hooked to coil - ? It is a grey shielded wire on my 84. Got continuity between between the ECU plug and fuel pump ground? Between coil - and the ECU plug ignition pulse wire? Not totally unheard of for the ECU fuel pump driver to fail.Mine did. 2 in a row seems unlikely though. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 29, 2012 Share Posted January 29, 2012 (edited) Apparently the engine will run if you ground the pump locally - but the way this old MPFI is wired the ground circuit for the fuel pump runs to the ECU and to some kind of ground "main junction" I would assume. (This is not how the EJ series computers are wired BTW - the fuel pump ground is just a chassis ground point not the ECU itself). So at this point the question is where is the problem - is it between pin 50 on the ECU and the pump, or is it one of the ECU's grounds (at the manifold perhaps?) that is the issue and pin 50 has no continuity with ground?.... Those are the tests that need performed. Check pin 50 for a ground connection and then check continuity on the wire from pin 50 to the pump. With the results of those tests we can move forward. GD Edited January 29, 2012 by GeneralDisorder Quote Link to comment Share on other sites More sharing options...
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