TPain Posted March 4, 2012 Share Posted March 4, 2012 So, I've got my car back finally from the mechanic who didn't know a thing about fixing electrical issues. Short story, after I attempted to jump my car from a dead battery, I blew a fusible link and some other mysterious grounding issue developed. The mechanic insisted that it was a grounding issue, not an ECM issue. Not wanting to take his word for it, I decided to test it myself and buy another ECM. This is the very strange part. My existing ECM provides no ground for the fuel pump, I have to ground the pump at the source for the fuel pump to work. The ECM that I got from a salvage yard, however, DOES provide the ground signal to the fuel pump but after I take it out of test mode (green connectors) the card doesn't even turn over; fuel pump works, car won't start. So, it appears that something this is an ECM issue and not a grounding issue like I thought. I'm going to try another ECM and see what happens. What you do you guys think? Link to comment Share on other sites More sharing options...
95legwagon Posted March 4, 2012 Share Posted March 4, 2012 is it a 5 speed or auto? maybe somethings goin on with the neutral safety switch? Link to comment Share on other sites More sharing options...
TheLoyale Posted March 4, 2012 Share Posted March 4, 2012 This could be due from a different year ECM. What year is this car? I agree with the Neutral switch safety. Link to comment Share on other sites More sharing options...
TPain Posted March 4, 2012 Author Share Posted March 4, 2012 (edited) Its an 85 GL10 turbo 4x4 automatic with approx 52k on it. The part number of the ECMs are all the same. Althe the housing for the salvaged ones are black and my original is electroless stainless steel. Edited March 4, 2012 by TPain Link to comment Share on other sites More sharing options...
ihscout54 Posted March 4, 2012 Share Posted March 4, 2012 (edited) The ECM that I got from a salvage yard, however, DOES provide the ground signal to the fuel pump but after I take it out of test mode (green connectors) the card doesn't even turn over; fuel pump works, car won't start. maybe somethings goin on with the neutral safety switch? Are you saying it wont even crank, or it just wont start? Does it start with the connectors hooked up? The part number of the ECMs are all the same. Are you sure about that? The SPFI ECM #'s changed like every year. I went through a no start nightmare when I changed ECM's. I too was informed that all black ECU's interchange. There were 2 wires whos pins were reversed going to the disty, took me a couple days to track it down. This was an '87 to '88 y.m. kinda change. Especially being an '85 you want to make sure you get an ECM with matching #'s. Things like style of MAF sensor on board might cause issues for you. but- I KNOW NOTHING ABOUT TURBO EA82 CARS! Edited March 4, 2012 by ihscout54 spelinh and gramer bad :) Link to comment Share on other sites More sharing options...
ihscout54 Posted March 4, 2012 Share Posted March 4, 2012 http://www.ultimatesubaru.org/forum/showthread.php?t=76906 Also give this a read as it may apply to this situation. Good luck. Link to comment Share on other sites More sharing options...
TPain Posted March 4, 2012 Author Share Posted March 4, 2012 The Subaru part number on the top are all the same, the second row of numbers below it are different. With my existing ECM, with my grounding the fuel pump to the body, it starts fine. With the replacement ECM, I don't need to ground it to the body (grounds works fine in test mode) but the engine will not crank, nothing. Link to comment Share on other sites More sharing options...
TPain Posted March 4, 2012 Author Share Posted March 4, 2012 I have seen that thread but where's the pic he's talking about showing transistor Q701? I never found it. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 4, 2012 Share Posted March 4, 2012 I think you may be onto something with the Q701 transistor - worth a check for sure. The pictures is in the zip file attached to that repair post... http://www.ultimatesubaru.org/forum/attachment.php?attachmentid=5039&d=1183545203 You will need a meter with a diode function and then you can refer to here on how to test it: http://www.learnabout-electronics.org/transistor_faults_02.php GD Link to comment Share on other sites More sharing options...
TPain Posted March 4, 2012 Author Share Posted March 4, 2012 Here's a pic of my ECM The problem is, there is no transistor Q702 listed on mine. Link to comment Share on other sites More sharing options...
TPain Posted March 4, 2012 Author Share Posted March 4, 2012 The photo of the Q702 transistor in Stickeyed thread is located at the top left corner below the cooling fins on the outside. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 4, 2012 Share Posted March 4, 2012 It's most likely T702 on your board. But the one that was a problem on his was Q701.... I would look for T701 and test that one.... Your's is an '85.... his may have been a later model hot-wire MAF unit. All the MPFI's from that era use this strange fuel pump ground through the ECU.... but I'm just speculating that his problem and your problem are similar. For all we know from reading the posts his problem may have been on the fuel pump relay driver side of the circuit. Certainly worth a test of a few transistors though. GD Link to comment Share on other sites More sharing options...
TPain Posted March 4, 2012 Author Share Posted March 4, 2012 I found a D702 and a T702. The T702 is a square vertical black piece, 1 of three pieces along the inside of the wall of the ECM. The D702 is buried on the bottom near that plastic glue, oblong shape. I've got my autometer on diode test. The manual says: Touch the test probes to the diode under test. Forward voltage will typically indicate .400 to .700V. Reverse voltage will indicate "OL." Shorted devices will indicate near 0V and an open device will indicate "OL" in both polarities. Sounds like Chineese to me lol. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 4, 2012 Share Posted March 4, 2012 You need to read the link I posted above. You will use the "diode test" function of the multi-meter but what you are testing is not, stricktly speaking, a diode. It is.... but it's most complicated than that because it's actually a transistor that is constructed with diode-like semi-conductor junctions...... The T702 sounds like the one you should test. It will have three legs on it that are soldered to the board. Read that link I posted above and it will quide you through how to test a transistor. GD Link to comment Share on other sites More sharing options...
TPain Posted March 4, 2012 Author Share Posted March 4, 2012 (edited) Okay, here's what I'm getting. I removed the circuit board from the ECM housing so that I could get access to the back of it to test the components. From left to right, the top right corner of my ECM picture: T702 0.982 T401, the green one, gives me 3.052 The last one, unsure of the number, gives me 2.623 Edited March 5, 2012 by TPain Link to comment Share on other sites More sharing options...
TPain Posted March 6, 2012 Author Share Posted March 6, 2012 It's fixed! Car runs fine. The culprit? A bad ECM, actually, two bad ones. My original ECM was bad and the one that the salvage yard originally sent me was bad as well. I just got the replacement and the car fired right up, grounding issue is resolved. Link to comment Share on other sites More sharing options...
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