darsdoug Posted September 19, 2015 Author Share Posted September 19, 2015 Bingo! I put a Harbor Freight fuel pressure tester between the fuel filter and fuel rail and I got zero pressure after three or four key-on prime attempts. I put the tester on my 96 wagon (just to make sure it was good) and I got 30psi on the first prime and 35psi on the second prime. Just goes to show you cannot overlook the obvious. Thanks guy's. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted September 20, 2015 Share Posted September 20, 2015 With all the injectors and the MAF unplugged the only codes you need to worry about are the TPS and the knock sensor code. Knock sensor won't keep it from starting but a TPS code might if it thinks you're holding the throttle open. Check voltage on the center pin of the TPS with the key On. You have to do this with it plugged in. Use a paper clip to back probe the connector. Should only have 0.45-0.55v on the center pin. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted September 20, 2015 Share Posted September 20, 2015 Or it could be fuel pressure... How far back did I say that... ? :cattle prod: Quote Link to comment Share on other sites More sharing options...
darsdoug Posted September 20, 2015 Author Share Posted September 20, 2015 (edited) I still haven't got it to run. I have the fuel pressure tester attached between the fuel rail and the filter and it's losing hold pressure (30psi) within seconds. I pinched off the return line that goes to the fuel tank and it held pressure great at 40+ psi. I then unpinched the return line and the hold pressure continues to drop off rapidly. So it's a bad regulator, correct? With tester connected before the filter it holds steady at 32psi (with the outlet end of the tester plugged of course) I might ad that the fuel relay clicks one time then pressure drops off immediately. I turn ignition key to "on" position (not crank) and I get 32psi. o.k.....Then 2 seconds later the relay clicks once (click coming from above my left knee) and the hold pressure drops like a rock. Whats up with that? Do I have a bad relay also? Edited September 20, 2015 by darsdoug Quote Link to comment Share on other sites More sharing options...
Dj7291993 Posted September 23, 2015 Share Posted September 23, 2015 When you turn the key on, the PCM will run the fuel pump for a few seconds (exactly how long varies by car. Subies seem to be shorter than most). If fuel pressure is dropping down immediately after, you have a leak somewhere. If you pinch off the line between the tester and the engine and it holds, you leak is over there. If it still drops off, your fuel pump is draining back, which is a problem. Most cars will have an initial drop when it kicks off of a couple psi, then they should hold. Can't remember what most specs are, but I want to say no more than a couple psi over a few minutes. If it's falling like a rock, somethings leaking off pressure, probably the pump if it's able to build it in the first place. Have you checked fuel pressure while cranking it? Quote Link to comment Share on other sites More sharing options...
darsdoug Posted September 26, 2015 Author Share Posted September 26, 2015 When you turn the key on, the PCM will run the fuel pump for a few seconds (exactly how long varies by car. Subies seem to be shorter than most). If fuel pressure is dropping down immediately after, you have a leak somewhere. If you pinch off the line between the tester and the engine and it holds, you leak is over there. If it still drops off, your fuel pump is draining back, which is a problem. Most cars will have an initial drop when it kicks off of a couple psi, then they should hold. Can't remember what most specs are, but I want to say no more than a couple psi over a few minutes. If it's falling like a rock, somethings leaking off pressure, probably the pump if it's able to build it in the first place. Have you checked fuel pressure while cranking it? I have the fuel pressure gauge attached between the fuel filter and the engine and I can see it clearly from the drivers seat. Although I haven't watched it when cranking, I'll do that today. It holds pressure fine when attached to the line coming from the gas tank so I assume the pump is not draining back. Quote Link to comment Share on other sites More sharing options...
darsdoug Posted September 29, 2015 Author Share Posted September 29, 2015 Jeez. I just had the TB on wrong. It starts right up and runs great now. Quote Link to comment Share on other sites More sharing options...
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