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1985 320 ignition woes.

Discussion in 'E30 (1984-1993)' started by jimbomac, Sep 14, 2012.

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    jimbomac

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    :( Following advice from MGarrison(thanks) I arrive here in search of help with sorting out the ignition system on my 1985 6 cylinder 320. I've carried out all the tests given in the Haynes book. This showed that the coil was bad so I replaced it. All other tests gave the correct readings but still no sparks. Has anyone had to deal with the BERU M038 ignition control module? I suspect this is the problem but don't know how to check it. Jimbomac
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    MGarrison

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    My Bentley manual says E30's with 4-cyl. engines have a transistorized coil ignition system (TCI-i) with an ignition control unit, distributor with impulse generator, and ignition coil. 6-cyl. engines it says use Motronic (DME) ignition system, with an ignition coil, motronic control unit, and distributor. Your question sounds as if you have a 6-cyl. using a TCI-i system?

    If you have a motronic system, and the distributor cap and rotor are in good condition, and the ignition coil tests good, then perhaps swap in a different motronic DME/ECU brainbox. Bentley manual says 84-87 eta-motored cars use two sensors to give the ecu engine speed and crankshaft postion, both located on the drivers side of the transmission bellhousing, taking their reading off the flywheel teeth and a pin on the flywheel. The speed sensor reads off the flywheel teeth, the reference sensor reads off a raised pin. Besides a bad sensor, a missing pin also would be a problem.

    Bentley manual has testing procedures for TCI-i ignition control units, although it says Bosch or Siemens, not Beru (albeit, for 4-cyl's), and for the eta-motor speed & reference sensors. Clarify what you have , perhaps what I have reference to here can be of help.
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    jimbomac

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    I now realize that I may have an odd 320, perhaps a 'transition' model. I do indeed have a 6-cyl with TCI. The Ignition control module is made by Beru but is in fact Siemens (two round connectors rather than the Bosch single rectangular connector). The ECU is a Bosch L 4 Jetronic unit.
    Many thanks for help,
    Jimbomac
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    MGarrison

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    With the caveat to proceed at your own risk since I don't have a scanner handy for pictures, if you have a round connector with 8 terminals, Bentley says to connect a voltmeter between terminals 6 and 3. 6 is in the center of the connector; orienting the connector so the cable is downwards, or cable exiting such that it's at the _bottom_ of the connector, then terminal one is at the 3 O'Clock position, 2 is at 5 O'Clock, and 3 is at 7 O'Clock (they are numbered counter-clockwise but for 6, in the center. There should be battery voltage when the ignition switch is turned ON. Check for continuity from terminal 6 to ground, and from 3 to terminal 15 of the coil (says the manual, it's not showing me where terminal 15 of the coil is).

    On the two-terminal round connector, connect a voltmeter (use 10VAC scale), pos. to pos, and neg. to neg. Bentley pic. shows looking AT the terminals/connection points, right is positive. Crank the starter and see if you're getting 1-2 volts AC. If low or none, check for continuity between the control unit connector and the distributor. It also says to check the impulse generator resistance and air gap (perhaps Haynes outlines that? - save me some typing later, if so.). If there's voltage but no spark, it says most likely ignition control is bad and should be replaced.

    You can see why the Bentley manual can be handy, if the testing procedures work for yours - ;) I presume Bentley is geared towards U.S. market cars, it's possible that E28's here were using the M20 engine, although with a larger displacement, with your type of ignition. You might want to pose your question over on mye28.com, there's a lot of expertise over there. Search the forums first though!
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    jimbomac

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    Thanks again for help-I'll take my chances and run the tests. FYI terminal 15 on the coil is numbered-the other terminal is 1.
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    jimbomac

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    Hello again. Ran the tests as suggested and all checked out fine except still no sparks. At this point I realised there was no way to check the ignition control unit. Bit the bullet and bought a new unit- €100/$130-ouch!. Worth it -sparks at last!
    My turn to be helpful (maybe!). Engine ran very erratically suggesting gummed injectors. Decided that removing the inlet manifold just to get at the injectors was not a good idea. Solution-disconnect the inlet fuel pipe from the 'common rail' feeding the injectors. Attach a short piece of fuel hose and a funnel to the 'rail' in place of the inlet pipe. Pour in neat injector cleaner and leave for 24 hours.Put it all back the way BMW intended. Start up and enjoy the sounds of the engine clearing its throat and running sweetly. Jimbomac
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    MGarrison

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    Not sure on your engine, but on M20B25 motors, the fuel injectors are held to the fuel rail by u-shaped clips; Bentley instructions are pretty basic, unbolt the fuel rail bolts (4 on M20's), and basically, carefully wiggle and pull the fuel rail to pull the injectors from the cylinder head, then it says pull the clips and pull the fuel injectors. Fuel injectors that have been in place for a long period of time can be really stuck in place and take a surprising amount of force/effort to get free.

    In any case, very glad you got it running - unfortunately, yes, no built-in diagnostic test for the DME or ignition control unit, you're left to a Sherlockian deduction by elimination of all other variables. So many E30's were made, often expensive electronic parts can be had off Ebay relatively inexpensively, depending on your risk tolerance. Cracked solder joints/lines on circuit boards seem to be a common issue on 80's-era bimmers, but stuff inside control units I suspect is just best swapped out for a known-good replacement.

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