Bruski Posted September 21, 2009 Share Posted September 21, 2009 2000 Subaru Outback 4 cylinder 106K miles Car wouldn't start on Wednesday. Diagnosed it as a no fuel condition. Checked fuel pump fuse and relay. Relay was suspect so I bypassed it. Still no start. Put a fuel pressure gauge on it, 0 psi. Replaced pump. Still no pressure but the pump is definitely running - low flow/no pressure. OK, hmmm Took out the new pump and noticed that the cap on the "accumulator" was cock-eyed and cracked allowing fuel to dump back into the tank. 'Course they don't sell that part separately. So I welded the old one back together and replaced the O-ring. Got pressure but still had to bypass the relay. Replaced the relay. Still nothing. I can get the relay to close and the pump to come on if I ground the switching side. The switching side is supposed to be grounded by the ECU. I found the wire where it goes into the ECU by continuity. I back-probed it and it shows constant ground (?). Hmmm. Maybe the ECU needs to be reset but there are no codes according to my reader. I've gone through the recommended procedure to reset it (disconnect battery, press brake pedal a few times and let sit for 45 min) but still nothing. What am I missing? I've thought about the possibility of a fried ECU but everything else works fine. All fuses check out ok and there are no codes. Suggestions?? TIA, Chris Link to comment Share on other sites More sharing options...
Fairtax4me Posted September 21, 2009 Share Posted September 21, 2009 I think it would pretty much have to be a bad ECU if the relay is not grounding. You're absolutely sure the relay is getting power from the fuse block? Link to comment Share on other sites More sharing options...
Bruski Posted September 21, 2009 Author Share Posted September 21, 2009 Positive. Like I said, if I provide a ground for the switching side of the relay, it starts and runs fine. Would the ECU function in all other respects except the fuel pump relay grounding? Link to comment Share on other sites More sharing options...
Fairtax4me Posted September 21, 2009 Share Posted September 21, 2009 I'm sure it's possible. One bad transistor is all it takes. Link to comment Share on other sites More sharing options...
Log1call Posted September 21, 2009 Share Posted September 21, 2009 (edited) Didn't you say the ecu was permanant earth? So, you are certain that your model does earth the relay, not power it? And whey you were checking it you did turn the key on and then test it within one and a half seconds right? Just checking. Edited September 21, 2009 by Log1call Link to comment Share on other sites More sharing options...
Bruski Posted September 21, 2009 Author Share Posted September 21, 2009 If it is the ECU, do I need to replace it or is there somebody that can fix it? How do I confirm that it is the ECU? It appears that there is a guy called the ECU doctor that repairs ECU's. Anybody have any experience with this company? They're in the UK somewhere, is there anybody in the US that repairs ECU's? Link to comment Share on other sites More sharing options...
Log1call Posted September 21, 2009 Share Posted September 21, 2009 But if the ecu has a constant ground at the fuel pump relay pin, and that's what the relay needs to switch the pump on, it should be running the pump constantly? Link to comment Share on other sites More sharing options...
Bruski Posted September 21, 2009 Author Share Posted September 21, 2009 That's part of the mystery. There is continuity from the ground side of the relay to the terminal on the ECU that I believe is the correct wire (same light green color, has continuity). Then, if I back-probe it, there is constant continuity to ground (???) no matter what the position of the key is. But, the pump never turns on unless I provide a direct connection from the relay to ground. That's what has me confused. Link to comment Share on other sites More sharing options...
Cougar Posted September 21, 2009 Share Posted September 21, 2009 (edited) My info says the wire color for the relay return wire is blue/green on pin A16 to the ECU. Check the voltage on that wire and with everything connected as it should be. Checking the voltage with reference to ground the voltage should be low for a couple of seconds as the pump should turn on with the igntion switch. If the ECU dosen't see ignition pulses it shuts down the pump circuit for safety. Do you have spark getting to the plugs? If not, check for power to the ignition system and the fuses. You should at least see the voltage on the pin go low for a couple of seconds when the key is turned on. If that doesn't happen and the voltage stays high then the ECU does have a problem. You can get rebuilt ones for a resonable price over a new one. Edited September 21, 2009 by Cougar Link to comment Share on other sites More sharing options...
Log1call Posted September 21, 2009 Share Posted September 21, 2009 The voltage check just mentioned needs to be between power and the ecu pin, not from the pin and earth. From the pin to earth there should be continuity but there won't be voltage. Second point... If you back probe the ecu, and it shows continuity to earth, then you turn the key on, and there is still continuity to earth, then the relay should operate. If the ecu was open circuit, or perhaps a high resistance to earth, then the relay would send the ecu's pin positive. Perhaps there is a high resistance in the circuit sending power to the relay. Then perhaps when you turn the key and the ecu earths it makes all the circuit, well all that is between the resistance and the ecu at least, earthed. Link to comment Share on other sites More sharing options...
Bruski Posted September 21, 2009 Author Share Posted September 21, 2009 Cougar - thanks for the info, that all makes sense. When you say pin A16 of the ECU, how is that referenced? Are the three plugs A,B, and C? How are the wires counted, left to right/top to bottom? I traced it by color/continuity but would like to confirm by pin designation. Thanks. Link to comment Share on other sites More sharing options...
Cougar Posted September 21, 2009 Share Posted September 21, 2009 The info doesn't show a connector color so it may be white. The connector (B134) has three rows of pins and the pin A16 is in the center of the middle row of pins. There are 7 pins on each side of it. To Log1call: When I stated that there will be voltage on the return side of the relay coil it is when the pump isn't running. There will be near supply voltage on the ECU pin when the pump is off (with ignition ON of course) or if the ECU is damaged internally. This is basically the same thing as an open switch connection would show. Link to comment Share on other sites More sharing options...
Log1call Posted September 22, 2009 Share Posted September 22, 2009 No offence intended Cougar. I missread/missunderstood your discription and thought it may need clarifying. It does read right to me now though that I have reread it. I must have been having a senile moment. Cheers. Link to comment Share on other sites More sharing options...
Bruski Posted September 23, 2009 Author Share Posted September 23, 2009 Thanks for all of the info and help, guys. It appears that the ECU is at fault. Which leads to the next question, who do you recommend to repair it? It appears that there are several companies ranging in price from $195 to $400. Or, I can get a new one from the dealer fro $640 or so. Suggestions? Link to comment Share on other sites More sharing options...
Cougar Posted September 23, 2009 Share Posted September 23, 2009 (edited) The ECUs don't have a lot of failures but they do now and then. I have fixed them before but I think your best bet may be to purchase one for around 200 dollars or check a salvage yard in your area to see if they may have one available. Here is a real deal if you use Ebay. http://cgi.ebay.com/ebaymotors/ENGINE-BRAIN-BOX-ECU-00-SUBARU-LEGACY-OUTBACK-GUARANTY_W0QQitemZ390089601254QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item5ad326f0e6&_trksid=p4506.c0.m245 Edited September 23, 2009 by Cougar Link to comment Share on other sites More sharing options...
Bruski Posted September 23, 2009 Author Share Posted September 23, 2009 D'oh! I didn't even think about Ebay. Thanks for the tip! It is on the way. Link to comment Share on other sites More sharing options...
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