Engine Fault Continues......

    After replacing both distributors and rotor arms which were in poor condition (as per previous post), I started her up this evening after a good clean up everywhere and still not right. She is only running on 1 bank it seems. Here are the symptoms:

    Bank 1-6 remove main coil lead and car won't start. Put back lead.
    Bank 7-12 remove main coil lead and engine sounds the same (i.e. appears to be running on one bank only)
    take no. 7 plug out and good regular spark.
    When restarted - both DK's operating (turning) but again only one bank running.
    Could it be fuel? Coincidently, the day she failed last week, I ran to nearly on red on tank and filled 78 Litres worth. An hour later this problem occured.

    Is it possible to test fuel flow easily? Could a fuel filter block so quickly? They were both changed (according to a service report I have 4 years ago, 6k miles).

    When revving up seems very sluggish on 1 bank,(guess that is to be expected)

    Any obvious tests please? She is off the road now :(

    Thanks

    Bob
    BMW 850CI

    Pop one of the faulty bank's sparkplug lead off at the plug and stick a spare plug in there with the plug balanced on the block. Run the engine and see if it sparking. That will reduce the possible causes at least.


    Although filters do not fizzle out quickly, pumps do. On the E32 you could swap the delivery pipes at the fuel tank to swap over the pumps - I'm not sure on the E31.

    Engine Fault Continues ...2


    Some further information that may help. Yesterday, I removed all 12 plugs and cleaned, gap checked and replaced and checked lead integrity. All OK. One thing to note on the bank that isn't firing is that all the plugs were soot black but not wet after I thought it was simply the distributor that had failed. the more I think of this, I believe that both distributors were working in a fashion and something else has caused this bank failure problem. After running tonight, removing a dead bank plug revealed that it looked exactly as I had cleaned it. Sounds like fuel issues?

    I suspect Fuel pump check? Where are they?
    Filter check? Is it possible to check without disturbing?

    Any help welcomed....

    Thanks

    Bob
    850CI

    Tried that and good spark on the dead bank plug resting on the engine casing.....

    Got to be fuel I reckon. Strange it can happen so quickly.

    Checked fuses 23 and 24 for fuel pumps. Both good

    Thanks

    Bob

    The fuel supply lines can be swapped to see if one pump has failed. The cover is under the right-hand rear seat. Have a read of the fuel-supply section in this:


    http://www.bmwtechinfo.com/repair/main/721en/index.htm

    Please do yourself a favor and get this car properly diagnosed, else you will likely be fishing in the muck for a while.
    There are numerous reasons why DME´s decide that one bank has to be cut off.


    There is a so called stomp test with which you can diagnose both DME´s of an M60/M70/S70 E31.
    This will possibly require you to install a dash bulb first (Check Engine Light/CEL) but then you can check the laid down errors for each DME simply by pressing the gas pedal a few times and observing the light pattern. This has worked for many M70 owners - not for some. Worth a try.


    Stomp test & codes


    After that you really ought to go to a place where proper MoDIC or DIS diagnostic equipment is available.


    Something as simple as a torn ignition lead e.g. directly on the plug 6 or 12 will effectively ground you. Leads 6 and 12 have donut shaped thingies on the distributor end which act as ignition sensors. If the ignition signal is not detected the DME will cut the fuel for this bank which in turn may make you believe in a problem of the fuel system.


    Keep us posted how you fared.


    Cheers
    Reinhard

    Thanks Timm, this will be this evenings project. I though there was a pump for both cylinder banks? Are both the pumps under one seat?

    Looking at the diagram of the filters they the fuel lines look as they go to the rear seat behind the passenger?

    maybe clearer when I get in there tonight.

    Thanks

    Bob
    850CI

    Thanks Reinhard,

    Step by step and hopefully will find what's going on. Can you PM the Stomp link - it seems broken here- thanks.

    Once I'm happy I've reached my limit of investigations. I'll have to take her to the local dealer at £100/hr :(

    Will press on....

    Thanks

    Bob

    Got it thanks. Which key switch position is "ON" is it when all the ignition lights come on and the EML light goes out after 2 seconds?

    Just tried that and no flashing light. Or is it position 1 or 2?

    Thanks

    Bob

    Another long evening here checking and checking. Nothing obvious found. No CEL lamp in dash, must get one of those.

    I finally decided to try a battery disconnect magic reset, but to no avail. The fault condition is still present.

    I jacked her up and the filters do look newish although I couldn't see a date on them but have done c. 5k miles.

    Looks like cheque book time up at the local dealer. They are good there and will be thorough and may find the issue.

    She is looking great at the moment so may just have to limp it there. I tried driving along my driveway tonight and she does feel as if in limp mode like when the EML lamp comes on. Odd... It maybe that is the mode she is in. Both sides of exhaust are getting hot as well, so maybe some cylinders fire in that mode. I'm not certain.

    Will keep you posted on how I get on over the next few days.....

    Depressed from Guernsey

    If both left and right exhausts are getting hot, then you may well have an ignition fault. It could be the sensor on the ignition lead, as has been mentioned. Also, have you checked the state of the ignition coils?

    Hi Everyone,

    I'm back in business!!! Excellent news here. OK so here goes:

    I took it to the local repair shop who are great guys, let you in the workshop, talk things over etc. Their BMW test kit wasn't functioioning at the moment but they had a generic one that could communicate with my 850. Indications were MAF failure 7-12 and Lambda sensor? I guessed that the O2 sensor was effect, not cause so thought carefully and realised that the shot distributors were red herrings but needed fixing?

    Got home and fitted the MAF that I recently got from Harry 8 (thanks!) fitted it and wow! Bingo! She started up immediuately and is so smooth now with the new distributer caps and rotors as well. So in the end MAF failure? I may strip it down and see if it is possible to repair or refurb. Unbelieveble. But feeling great now - she is lovely..

    Thanks for all the advice and help. Slowly starting to understand her...

    Have a great weekend

    Bob :drink1:

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