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    #1

    Confirm My Suspicions.

    Car is an early body 85, two fuel pumps. Low pressure in tank, high pressure external pump. I replaced the in tank pump about 3 or 4 years ago.

    So I had a small intermittent problem for a while. Car would hiccup, so to speak over rough, bumpy tarmac. Thinking it was either fuel or electrical related, but too intermittent to diagnose.

    Fast forward a month. Car gets driven rarely, as I'm commuting in the discovery. Take the car out for a Sunday drive. Runs awesome throughout the day, nice mountain drive no problems. On the return trip car really starts hiccuping. Basically felt like fuel cutting out, all electrical systems were fine.

    Car makes it back, drives around town with moderate issues. Later that evening, after some fun iracing with some friends, driving home at midnight car would cut out, sputter, than die. I would check for any loose connectors, but to no avail anything. Would have to wait a few minutes and car would start and run fine. Happened repeated times, ended up leaving the car in a safe place and drive home the next day.

    What I noticed:

    Hiccuping felt like momentary fuel cutting
    Hiccuping happens on bumpy roads (car has mostly solid bushings)
    Car would die on uphill during load.

    My suspicion at this point is 90% the high pressure external pump. Anyone have any other suggestions?
    1985 M10b18. 70maybewhpoffury. Over engineered S50b30 murica BBQ swap in progress.

    Originally posted by DEV0 E30
    You'd chugg this butt. I know you would. Ain't gotta' lie to kick it brostantinople.
    Tags: None
    #2
    They recommend you change both pumps when one goes bad since the other is likely to follow. Try another main pump.
    "I'd probably take the E30 M3 in this case just because I love that little car, and how tanky that inline 6 is." - thecj

    85 323i M TECH 1 S52 - ALPINEWEISS/SCHWARZE
    88 M3 - LACHSSILBER/SCHWARZE
    89 M3 - ALPINEWEISS II/M TECH CLOTH-ALCANTARA
    91 M TECHNIC CABRIO TURBO - MACAOBLAU/M TECH CLOTH-LEATHER

    Comment

      #3
      Get an inline fuel pressure gauge and put it on the windshield under a wiper arm and watch fuel pressure during one of these issues.

      Sounds like a bad connection somewhere. Though it could be external pump. But at this point just throwing parts at it could fix things..
      But might not. I'd maybe change the external regardless because of its age.

      Have you inspected your main and fuel pump relay?

      Sent from my Galaxy Nexus using Tapatalk 2
      -Build http://www.r3vlimited.com/board/showthread.php?t=295277

      Comment

        #4
        Originally posted by reelizmpro View Post
        They recommend you change both pumps when one goes bad since the other is likely to follow. Try another main pump.
        When My main pump died, The other lasted another 3 or 4 years, lol.

        Originally posted by FLG View Post
        Get an inline fuel pressure gauge and put it on the windshield under a wiper arm and watch fuel pressure during one of these issues.

        Sounds like a bad connection somewhere. Though it could be external pump. But at this point just throwing parts at it could fix things..
        But might not. I'd maybe change the external regardless because of its age.

        Have you inspected your main and fuel pump relay?

        Sent from my Galaxy Nexus using Tapatalk 2
        I haven't checked the relays. Next time I'm with the car I will check them out.

        Electrical is what I thought until it began to die on me. Fuel pump would be both electrical and fuel though.
        1985 M10b18. 70maybewhpoffury. Over engineered S50b30 murica BBQ swap in progress.

        Originally posted by DEV0 E30
        You'd chugg this butt. I know you would. Ain't gotta' lie to kick it brostantinople.

        Comment

          #5
          I would guess the resistor strip in your AFM is nearly worn through.

          Comment

            #6
            Originally posted by Ryann View Post
            I would guess the resistor strip in your AFM is nearly worn through.
            Can't say I have heard about that before. Car is an M10.
            1985 M10b18. 70maybewhpoffury. Over engineered S50b30 murica BBQ swap in progress.

            Originally posted by DEV0 E30
            You'd chugg this butt. I know you would. Ain't gotta' lie to kick it brostantinople.

            Comment

              #7
              A poor connection between the barn door contacts and the resistor strip under the black plastic cover on your AFM feels just like a fuel pump cutting out.

              Comment

                #8
                Originally posted by Ryann View Post
                A poor connection between the barn door contacts and the resistor strip under the black plastic cover on your AFM feels just like a fuel pump cutting out.
                Will definitely take a look at it.

                Keep up the suggestions guys, a lot of things I have missed, or not thought of.
                1985 M10b18. 70maybewhpoffury. Over engineered S50b30 murica BBQ swap in progress.

                Originally posted by DEV0 E30
                You'd chugg this butt. I know you would. Ain't gotta' lie to kick it brostantinople.

                Comment

                  #9
                  Where is a main ground on an m10? Oil pan like the m20?
                  Doesn't hurt to check that while you're at it.

                  1991 325iS turbo

                  Comment

                    #10
                    Originally posted by ak- View Post
                    Where is a main ground on an m10? Oil pan like the m20?
                    Doesn't hurt to check that while you're at it.
                    Can't remember if it was the upper pan or not. Did replace it a year or so ago with the rest of my ground straps.
                    1985 M10b18. 70maybewhpoffury. Over engineered S50b30 murica BBQ swap in progress.

                    Originally posted by DEV0 E30
                    You'd chugg this butt. I know you would. Ain't gotta' lie to kick it brostantinople.

                    Comment

                      #11
                      Does the M10 have the c101 connector (or similar)? If so I'd check that. I had the exact same symptoms and it was a correded c101 connector. Run great for an hour, hit a bump and it all went to shit. Couple times I almost didn't make it home.
                      90 325i DD/Track
                      03 Durango 5.9


                      Originally posted by e30mpg
                      It is recommended to get new gasket but this is R3v and we just copper spray that shit......slap biotch on and tighten to tq.

                      Comment

                        #12
                        Originally posted by Holland View Post
                        Can't remember if it was the upper pan or not. Did replace it a year or so ago with the rest of my ground straps.
                        I would check to be sure that the main ground strap is tight enough. I had a problem with mine, every time I took a turn it would start to behave like you said.

                        Comment

                          #13
                          the external one will make a load buzzing noise when failing. Also check plug at fuel pump, mine had a bad connection or wire and would cut out on bumpy roads. I would wiggle wire and it would go again. Owner before me put a new pump in thinking it was the pump but wasn't, just a connection.
                          "I wanna see da boat movie"
                          "I got a tree on my house"

                          Comment

                            #14
                            My biggest suspicion is that when the car would actually die, I would have to wait a few minutes for startup, it would not immediately restart. then run fine until the next hill.
                            1985 M10b18. 70maybewhpoffury. Over engineered S50b30 murica BBQ swap in progress.

                            Originally posted by DEV0 E30
                            You'd chugg this butt. I know you would. Ain't gotta' lie to kick it brostantinople.

                            Comment

                              #15
                              Were you down to around the last 1/4 of your tank when this occurred? If so, you could have junk/debris at the bottom of your tank that is causing the hiccups by clogging the screen pick-up in the tank. Debris at the bottom of old E30 tanks is common. See if driving with a mostly full tank avoids the problem. If so, you can avoid fixing temporarily by keeping your tank full. However, the long term fix is either buying a new tank or the cheaper (but more labor intensive) jlevie suggested fix (search it out).

                              Obviously, I would listen for the whine of death from your fuel pump and probably swap out your fuel filter (as it may be clogged with junk from the bottom of your tank). There could obviously be several other things related to fuel delivery... just trying to cover all bases as this wasn't mentioned above.

                              Good luck and report back.

                              -Marc

                              Comment

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