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    M50 help!

    Hey everyone. This is my first BMW ('89 E30 with M50TUB25 swap, with S50 Cams), so I'm not very familiar with the car. What I'm having is an idle/stalling issue. I've done a lot of research, and yes I've seen this all over the forums, but I think I have a unique circumstance and wanted to double check with people who know these cars before I start throwing more money at parts.

    When I bought the car in July it was running very very well. About two weeks after the purchase I noticed a leak in the gas tank when full (rusted out around the pinch weld). I lifted the car and pulled the old tank. I replaced the tank, all the hard fuel lines, all the hard brake lines, fuel pump, and sending unit. I also pulled the carpet and repaired all the rust, so I was welding on the car, and had the DME out. While I was under there I also pulled the expansion tank and replaced the lines there as well. So basically entirely new fuel system from the filler neck to the rail.

    Now that I've put the car back down, it is idling rough, and sputtering until it stalls. As the RPM's drop all of the lighting operating off of electrical is dimming out. If I hold the gas down to keep the rev's up, it runs fine.

    So far I have:
    -Changed oil and filter (before starting the car)
    -Replaced the battery (which tested "bad" at Autozone)
    -Put in new plugs (old ones were very black and a little wet with fuel when I pulled them)
    -Cleaned ICV
    -Cleaned MAF
    -Checked lines/connections for cracks (including intake boot and hoses coming off of ICV)
    -Cleaned connections at battery and grounds everywhere (to make sure the engine is getting full power from the battery)

    Does anyone have any thoughts on what would cause a perfectly running car to act this way after sitting for a few months, combined with what I did to it during that time? Any help is greatly appreciated, and just so I don't get flamed with the "search" response, I've spent HOURS reading up on this topic, and all I've found are dead ends.

    Thanks for reading.
    sigpicLevel Motorsport: www.levelmotorsport.com

    Instagram: https://www.instagram.com/levelmotorsport/

    Facebook: https://www.facebook.com/LeVelIndustries/?fref=ts

    #2
    -Have you checked to see what the alternator is putting out for voltage?
    -The ICV can gum up from sitting and they don't always take well to cleaning. A "t" shaped ICV from an E30 is the same thing, maybe somebody local has one laying around you can swap out to verify.
    -Have you checked for vacuum leaks with either a smoke test or some carb cleaner? It's possible something got moved while you were working on it.
    -Are your fuel lines connected properly?
    -Checked fuel pressure at the rail?

    Comment


      #3
      -I can't get the car to run long enough to get a read on the alternator. I usually check for a voltage increase at the battery. I can't check it if it's not spinning.

      -I don't have anyone local that I can do an ICV swap with to test, unfortunately.

      -I did a full vacuum test today and the front end of the car is tight as can be. I also went over all of the fuel line connections from the fill neck to the rail and they are all tight.

      -I'm 99.99% sure. One thing that seems odd is that I am getting fuel at the front of the rail (inlet), but the return line (near firewall) is bone dry. Even if the pressure regulator was broken you would still have fuel at the very end of the rail, correct? What could stop the fuel from going all the way through the rail?

      Thanks for taking the time to respond. I'm moving in three days, so between trying to pack a truck I'm trying to get the car running so I can get it on a trailer...
      sigpicLevel Motorsport: www.levelmotorsport.com

      Instagram: https://www.instagram.com/levelmotorsport/

      Facebook: https://www.facebook.com/LeVelIndustries/?fref=ts

      Comment


        #4
        Okay, more info.

        -Tested fuel pressure at the pump.....48 psi with relay jumped
        -Tested fuel pressure at the front of the rail......43 psi with relay jumped
        -Tested fuel pressure at the front of the rail trying to start the car.......20 psi when it starts and as the pressure falls so do the RPMs all the way to stall.
        -put dump line off return side of rail into a bucket, then jumped relay, no fuel return.
        -put air into inlet side of rail. No air came out of the return.

        Is it safe to assume that there is a clog in the rail somewhere? Would that cause fuel to back up in the system, put additional electrical strain on the pump trying to push it through causing the plugs to have difficulty firing? The fuel backup would foul the plugs for sure.

        Does this sound right? Is the rail just bad or could this be an injector issue as well?
        sigpicLevel Motorsport: www.levelmotorsport.com

        Instagram: https://www.instagram.com/levelmotorsport/

        Facebook: https://www.facebook.com/LeVelIndustries/?fref=ts

        Comment


          #5
          I don't think it is an injector issue, sounds like something might have clogged your system. Try to blow out the rail and report back.

          Comment


            #6
            Got crazy with the carb cleaner in the rail and some nasty shit came out, and a new fuel pressure regulator is on the way. The FPR appeared to be original. We'll see.
            sigpicLevel Motorsport: www.levelmotorsport.com

            Instagram: https://www.instagram.com/levelmotorsport/

            Facebook: https://www.facebook.com/LeVelIndustries/?fref=ts

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