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1991 325iX No Start and I'm running out of ideas

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    1991 325iX No Start and I'm running out of ideas

    Short background: I tore down the top end to replace the head gasket, which had a leak. It started prior to me doing so. This is the first time I've ever done it, but everything seems to have gone well enough. I got the head machined, and the valves looked at from a highly reputable machine shop in my city, and put back together more or less without issue. I gapped the valves to spec when putting everything together. While I was doing that I also replaced the timing belt, drive belts, thermostat, water pump, fan clutch, radiator, throttle body gasket, exhaust manifold gaskets, intake manifold gaskets, and return line gasket (little triangular one off of the intake manifold to the fuel pressure regulator). Now it won't start. The engine cranks, and I'm getting a nice even churn from the starter. It feels and sounds strong, but it won't turn over. Not even a little bit.

    So far I've done/checked the following:
    - new crankshaft position sensor
    - new spark plugs (NGK)
    - spark plugs are gapped and seated correctly
    - new ignition coil
    - new distributor cap
    - new distributor rotor
    - new fuel hoses and hose clamps, all three (main line was cracked and leaking)
    - tank drained and new gas put in (it had been sitting a while, and wanted to make sure i wasn't putting bad gas through)
    - physically made sure fuel was coming from the main line
    - since fuel is coming through the line i'm assuming the fuel pump and subsequent relays are working
    - checked the fuses, and anything that seemed like it would be pertinent looked unbroken and functional

    What I haven't checked yet (and is a constantly diminishing list):
    - other relays, not really sure how to check those
    - ignition wire harness (though that's next to be replaced since i'm already here replaced everything else)
    - fuel pressure could be a problem, and i haven't checked it yet
    - DME (i really don't know how or why this would've gotten borked in this whole process, so I haven't figured it as a possible issue)
    - Fuel injectors, maybe?
    -Compression

    Really that's it. I'm a novice at most of this, and all the knowledge I have is academic from a metric ton of googling and reading. Are the things I haven't checked yet even a likely culprit? Are there things I'm not finding or thinking of? Any and all advice would be greatly appreciated.

    Thanks!

    #2
    Reversed supply and return lines?

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      #3
      I thought that too, so when I replaced the fuel hoses I literally held them both with rags on the ends to see which one produced fuel as someone else turned the engine for me. I'll admit, not the safest approach, but effective. That one went to the rail, and the other one to the Fuel Pressure Regulator.

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        #4
        The connector for the CPS and one connector that comes off the Spark Plug Wire Set use the same connector and are in pretty much the same location. I'd double check and make sure they are connected to the correct components!
        clutchCTRL!
        Move with a purpose.
        - 1991 325iX 4dr/5spd
        - 1976 2002 SlickTop/2.7i M20/G260
        - 2000 323i AT
        2016 Mazda CX3 Sport AWD

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          #5
          That is actually an excellent suggestion. I was fairly certain that i had gotten the right connectors to the right locations, but maybe not. I'll check that and update. I even know the exact ones you;'re talking about, and yeah, I can see a swap being made there unintentionally, and unnoticed.

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            #6
            I recommend to perform some electrical tests that are outlined in the DME troubleshooting section of the Bentley repair manual. This test will walk you through each DME input and output to verify all sensors and signals are there. The manual also has a troubleshooting section specific to the cranking/no start condition.
            Owner - Bavarian Restoration
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              #7
              make sure the orientation of both the front trigger wheel (crank pulley), and the distributor gear, are correct. seen it happen more than once. confirm your fuel lines are correct (feed hose does not connect to the pressure regulator) and confirm that the CPS and pulse sensor plugs were not accidentally reversed.

              A
              Portland, Oregon
              E28M5 | E30S50 | E30M3

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                #8
                These are great. Father of two little girls so I haven't had a chance to actually try any of these, but I'm listening and taking notes. It's greatly appreciated.

                Comment


                  #9
                  Alright, was able to get some time under the hood. The CPS and Pulse sensor connections don't seem to be swapped around. I went ahead and swapped out the ignition wires for an entire new loom. If I'm understanding e30austin correctly, I believe the crank pulley and distributor are on correctly. The distributor seems to only go one way since there's three screws and only one direction it can face. Got a compression gauge and did a compression test and everything seems great (which is honestly a relief...i really didn't want my head gasket work to be the cause). The pressures came back with:
                  C6: 140
                  C5: 150
                  C4: 145
                  C3: 142
                  C2: 138
                  C1: 135

                  Still not starting.

                  Comment


                    #10
                    So, update to the update:

                    I checked for spark on all 6 cylinders, and they're getting spark. I just pulled the fuel pump fuse, unseated each spark plug one at a time, set each on the valve cover, and had someone turn the engine over to view the spark. After some reading on checking for fuel at the rail I put everything back together, tried to start the car, then immediately went and unseated the spark plug from cylinder 1 to see if it's wet. Definitely didn't feel wet, and didn't even smell like fuel. Since it's not compression (yay), and it's not spark (also yay), I'm assuming this is the problem. I checked the C191 plug for the fuel injector rail to see if I was getting power. I have no idea what I'm doing in this regard, but I put the key in the ON position, and checked each pin in the C191 to see if they were at least getting power. They were (all but one, I think, which I read things correctly, that's normal). I can't interpret the numbers at all, but numbers happened (guidance in that realm would be helpful). I suppose it's possible that the injectors are flogged, but all 6 at the same time? Is that even a thing? It feels unlikely.

                    Any thoughts?

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                      #11
                      Originally posted by thedodd View Post
                      So, update to the update:

                      I checked for spark on all 6 cylinders, and they're getting spark. I just pulled the fuel pump fuse, unseated each spark plug one at a time, set each on the valve cover, and had someone turn the engine over to view the spark. After some reading on checking for fuel at the rail I put everything back together, tried to start the car, then immediately went and unseated the spark plug from cylinder 1 to see if it's wet. Definitely didn't feel wet, and didn't even smell like fuel. Since it's not compression (yay), and it's not spark (also yay), I'm assuming this is the problem. I checked the C191 plug for the fuel injector rail to see if I was getting power. I have no idea what I'm doing in this regard, but I put the key in the ON position, and checked each pin in the C191 to see if they were at least getting power. They were (all but one, I think, which I read things correctly, that's normal). I can't interpret the numbers at all, but numbers happened (guidance in that realm would be helpful). I suppose it's possible that the injectors are flogged, but all 6 at the same time? Is that even a thing? It feels unlikely.

                      Any thoughts?
                      check the c191 ground wire, to make sure it didn't fracture. in my experience, that's usually the one that fails. have you confirmed your fuel pump is working when cranking the engine? did you confirm the fuel lines are properly oriented?
                      Portland, Oregon
                      E28M5 | E30S50 | E30M3

                      Comment


                        #12
                        e30austin , so I went out and checked the C191 plug again, and upon closer inspection, it looks like one of the female points is no longer there? Definitely looks strange. Not sure if that's normal or not.

                        Also, to answer your questions: I held the fuel supply line and return line in my hands with rags over the end to make sure one of them was getting fuel. I couldn't remember which one was which, and that felt like the clearest way to tell. I put that one on the rail.

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                        Last edited by thedodd; Today, 10:41 AM.

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