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Thread: Finally my first problem - M70 - 6 cylinders only

  1. #1
    Join Date
    Oct 2010
    Location
    Kansas City, Missouri
    Posts
    2,212
    My Cars
    89 750iL | 91 325iX

    Unhappy Finally my first problem - M70 - 6 cylinders only

    Ah gotta love it. Hit a bump as per normal on the highway and one minute later I am down on 6 cylinders.

    Of course I found out now my Peake scanner wont scan the engine code it throws and the stomp test prompts nothing

    Start from the basics - all wires look good - cat back exhaust was already disconnected to replace hangers, cats look clear. Bank 1 is down.

    Pulled intakes confirmed DK motors were operating the throttles correctly - slightly opening upon turning car to run

    Swapped MAFs from side to side - No start

    Swapped MAFs back to original sides - No Start

    This would be a lot easier if Peake tool worked as adveritsed

  2. #2
    Join Date
    Oct 2010
    Location
    Kansas City, Missouri
    Posts
    2,212
    My Cars
    89 750iL | 91 325iX
    It seems the fuel tank breather hose was broken under the left DK motor. Unsure if this would affect anything overall.

  3. #3
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,655
    My Cars
    11/88 E32 750iL+98 E36M3
    About 15 years ago my 750 went into limp mode, tried a lot of things, in the end I checked the pins in the X20, X21 and the diagnosis port, and there were 2 pins which slipped out/down from the plugs, read this http://www.bimmerboard.com/forums/posts/146719 details / file http://www.bimmerboard.com/members/h...X20%20data.xls
    That could also be the reason that your Peake cannot read faults
    Is the EML light coming on when you switch ignition on and then goes out?

    Fuel tank breather valve broken/hoses broken causes unstable idle etc as there is unmetered air going into the system, but the engine should start.
    Last edited by shogun; 05-04-2019 at 10:21 PM.
    Shogun tricks and tips for the E32 series are HERE!

  4. #4
    Join Date
    Oct 2010
    Location
    Kansas City, Missouri
    Posts
    2,212
    My Cars
    89 750iL | 91 325iX
    No EML light and check engine light is intermittent

    Found torn intake boot, severed fuel breather hose and possible bad fuel pump as the one fuel line had no pressure or was 'soft' to squeeze while the engine is running.

    Always had an issue with the car slow starting and then only one bank firing up and then the next bank would fire off as well.

    It actually started up the other day on all 12 but then when I went to restart it, it was only running on 6 again.

  5. #5
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,655
    My Cars
    11/88 E32 750iL+98 E36M3
    Test the fuel pumps, first the easy way as I always do that: ignition off, open the fuse box, use a short cable for the distance from B+ and hold it briefly in top of the installed fuse 23 and the 24, see page 0661-03
    http://shark.armchair.mb.ca/~dave/BMW/e32/e32_89.pdf
    Before doing that, squeeze the 2 fuel hoses coming up left hand side engine bay and do the same after you gave power to the fuses. The fuel pumps will prime for a moment then. As engine is off, one can easily hear each fuel pump when they start pumping, also the fuel hoses should then under pressure afterwards. In case you need new fuel pumps and you want to do it cheapest, get 2 for E36, they will do so.
    Get some with the old style bolt/screw connector, the new Bosch pumps come with a plug with pigtail, so you would have to convert. I posted the dimensions of the pumps 1 year ago, when my pumps (then 28 years old) suddenly died
    http://www.bimmerboard.com/forums/posts/1264560/
    for a test for volume you can test like this , fuel pump relay on your 1989 is K210 and K211 , see page 0660-03
    http://bmwe32.masscom.net/sean750/fu...Regulators.htm NOTE: the fuel pump relays in this link are in a different location than on yours, the older 750 have the main relays and the fuel pumps relays just in the opposite location.
    Next would be a fuel pressure test.
    Shogun tricks and tips for the E32 series are HERE!

  6. #6
    Join Date
    Oct 2010
    Location
    Kansas City, Missouri
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    2,212
    My Cars
    89 750iL | 91 325iX
    I will test the fuel pressure tonight. Hopefully I got the right pumps as I ordered Bosch pumps for the 750, part number pulled from realoem was about ~$137 each.

    After playing with sensors on the intake I don't think it would be anything else besides fuel supply with previous issues I have had but we shall see.

  7. #7
    Join Date
    Mar 2013
    Location
    Green Bay, WI
    Posts
    1,332
    My Cars
    1992 750il / 1991 560 SE
    $137 a pump? Thats a steal if that is what you ended up paying. But there are much less expensive pumps that are a direct fit. I have a thread on them. About $35 each, which is crazy cheap. But while I have not had my car on the road much the last couple year they pumps worked great and are still doing fine.

    FYI the engine can run on one pump if you do some fancy plumbing. Good for testing. Does sound like you have a weak pump though, or one with a failed check valve.
    ______________________________
    1992 750iL

  8. #8
    Join Date
    Oct 2010
    Location
    Kansas City, Missouri
    Posts
    2,212
    My Cars
    89 750iL | 91 325iX
    Got the pumps in late last night, they are the newer bosch design so I will have to convert the wiring to pigtail vs the terminals

    Not a major issue but I may put this off till the weekend to play with so I can finish it off with some nice soddering instead of doing a hack job

  9. #9
    Join Date
    Oct 2010
    Location
    Kansas City, Missouri
    Posts
    2,212
    My Cars
    89 750iL | 91 325iX
    Update:

    Finished up the install of my new bosch fuel pumps. Originals from 1988 were still in the car. Did a bit of sodering on the fuel level sender as well.

    Had a fair amount of metal flake at the bottom of the tanks at the fuel pump inlet. Guessing one shelled itself out or something and it looked to be aluminum. Tank was full of fuel which made it impossible to clean it out.

    Plan on going back in to change the pickup filter all the full lines and sender unit so I'm not overly worried.


    Long story short, problem solved and overall a pretty easy job if you have worked with something similar before

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