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BMW E30 Stalling And No-Start

April 2, 2010

This answer is applicable for many BMWs in addition to the one listed below.

Q
car year: 1987
car model: 325is
Randomly my 325is will die. It doesn’t matter if I’m driving slow or going down the freeway. I may have to sit from 2 minutes to 30 minutes before it starts. There seems to be no set circumstance that sets this off. The car may be cool or operating at full temps. This may only happen once a month, or it might take place two or three times in a day. It truly has me baffled.

A
Unfortunately, we can only diagnose your dying/stalling and no-start issue while it is actively happening. Therefore, you’ll need to be prepared to do some testing when the symptoms occur. See the Fall 2007 issue of our Bavarian Autosport Fast Times newsletter, which contains a DIY article on diagnosing “no start” issues. You will need to use the diagnostic flow path outlined in the article when the engine dies and will not re-start. Once we have some answers on the diagnostic tests (is there spark, injector pulse and the fuel pump running) we can determine further diagnostics. These general steps would apply to any BMW that is having a no-start problem.

With the above points noted, your symptoms do fit into those for a weak main engine management relay or fuel pump relay. If you’re inclined to “throw something at it” I would suggest these two relays. They are relatively inexpensive and may actually fix the problem. If they don’t, we’re back to the no-start diagnostics, in order to prevent any further throwing of parts.

Engine Management, Fuel pump and Oxygen sensor heater relays on E30 chassis:


Click below for the Fall 2007 Fast Times newsletter:

Click below for E30 Engine Management Relay:

Click below for E30 Fuel Pump Relay:

12 Comments
  1. ted lovejoy permalink

    This happened to my 1987 325 and it was the “flywheel” sensor. it took BMW 8 hours to find it……. hopefully you will not have to pay for all the labor costs to diagnose the problem for a fairly cheap part.!!!!

    Note from Otto:
    Thank you for this comment. Yes, the flywheel position sensor will prevent a restart (however, the engine will run until it is shut-off … it will then not restart). In this case, you would find that there is no spark and no injector pulse, but the fuel pump would be running, since both the ECU and the fuel pump relay are functioning properly. A faulty position sensor will prevent the ECU from outputting the spark and injector signals.

  2. Ben permalink

    This is also happening to my 1987 325es. I have changed AFM, ICV, ICM, Cold Start Valve, Ignition wire, Spark plugs, All three sensors, Fuel injectors, and the exact same problem exist. They have told my my car does not have Flywheel sensor. Can some one tell me if my car has it, and if it does, where to look for it. My 1987 325es was built on October of 1986. I have the rough start and occasional stall as was explained above. To remedy this problem (not solving it) I have to unplug and replug the ICV then the rough starts will go away and same thing for stall, which the car starts okay after unplug and replug of the wire to ICV. This problem has cost me over 2000 dollars to fix but it has not been fixed yet. Thanks in advance for any help.

    • All 325e models do indeed have two sensors that are installed in the transmission bell-housing. They are located on the driver’s side at the front of the bell-housing (they read the side of the flywheel). One sensor reads the ring gear teeth (RPM sensor), the other reads the flywheel/crankshaft position pin, just behind the ring gear (crankshaft position sensor). While you could have a faulty RPM sensor, the engine would not start (no spark & no injector pulse) if the position sensor were faulty. You could try swapping the two sensors (they are the same) and see if the symptoms change (note that the plugs must be swapped as well as the sensor mounting positions). If they do, one of the sensors is faulty.

      Keep in mind, the idle control valve (ICV) only varies the amount of air that is bypassing the throttle, when the throttle is closed (at idle). The valve opens and closes to keep the idle at a given speed ….. just as if the throttle were being opened and closed. The ICV does not do anything with fuel mixture. If all of the parts that you mentioned had been replaced, the only thing left is the Engine Control Unit (ECU). I do not suggest that you just purchase one without testing with one that is known to be good.

      During the next no-start, let’s be sure to test for spark and injector pulse. This will help greatly in guiding the diagnostics.

  3. Ben permalink

    Oh, I forgot to mention that I have also replaced the two relays that was mentioned above. The fuel pump relay and the ECU relay.

  4. jobob permalink

    Had similar troubles with 89 m3
    It was o2 sensor.

    • Typically, a faulty O2 sensor will not cause a no-start. Of course, it certainly can cause drivability issues.

  5. Sean Bimmerman permalink

    I am experiencing similar problems with my 1990 e30 convertible. I was driveing on the highway yesterday when my engine suddenly shut down then seconds later while still coasting regained power . A few km’s down the road it did this again then just cut out completely .I tried restarting the engine with no sucess. after approx 10 mins while on the side of the highway I tried it again and she started ! So I kept going being about 380 km’s from the nearest town … Low and behold the car started this again approx 15 mins later! The car kept cutting out and comeing back on then quit again and I coasted to the side of the highway once again ! So this time I let it cool down a bit maybe 15 mins and she started again ! I took off and didnt even go 2 kms when it died again and finally would NOT restart and I had to get towed this time !!! Car cranks over real good , Fuel pump works fine cause I jumped the pins to test it and it seems to work fine. When I turn the key I hear faint but audible clicks near the front driver side of the car but I assume this is normal ??? Also I have checked the MAIN relay by jumping the pins and turning it over with no success … My immediate thought after pouring over online forums is that the CRANK POSITION SENSOR is shot . Before running out and getting one I wanted to make sure ~is there any way I can perform a test that does not require a volt meter to see if its shot ?

    • Ok, let’s get the basic diagnostic tests out of the way, so that we will have an idea of what direction to proceed.

      Test for spark and injector pulse, as outlined above. Let us know what you find. If there is no spark and no injector pulse, we could be dealing with the main ECU relay, the crankshaft position sensor, the ECU or a wiring problem (make sure that all of the wires at the positive junction block, on the passenger side firewall, are secure and tight).

      We don’t have a test for the crank sensor that does not require a multi-meter.

  6. Sean Bimmerman permalink

    Good news ! I was getting ready to swap out my crank position sensor when I noticed he other one was covered in road grime and engine grease , I cleaned it off real good sprayed with wd-40 and there ya go my car started immediately , went for a drive with it and it runs perfect ! So I was right about the cps just it wasnt screwed up just dirty lol

  7. Sean Bimmerman permalink

    It was a CPS I cleaned it and the car started 1st try ! Thanks guys this site is a huge help without it i may have needed a garage/mechanic

  8. Evan permalink

    I am having a similar problom with my 86 325es. It will randomly stall. Sometimes it will go a week or two without stalling somtimes minutes. I have replaced all three relays, fpr, rpm sensor, aux fuel pump, fuel filter, dme temp sensor and there is still a stalling problem. I have also bypassed the obc. It is getting spark as it will start with starter fluid(This will get it running sometimes but will usually die after the fluid is gone. It dosent seem to have injector pulse. I am at a loss. I cant figure it out.

    • If, during the no-start condition, you do have spark, but no injector pulse (have you actually tested this?), the problem will either be internal to the ECU or in the wiring between the ECU and the injectors. The power to the injectors comes from the main relay, so this would not be at fault, if you do have spark.

      Have you actually done the “trinity” of no-start diagnostics? Tested for spark, injector pulse and fuel pump operation?

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