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Starter or battery?

Discussion in 'E34 (1989-1995)' started by slinky66, Jul 30, 2008.

    slinky66 guest

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    Just this morning, my '95 525i cranks enthusiastically but will not turn over. I have been driving the car pretty regularly this summer too. I have a BMW battery that's about 2 years old and I do not think the starter has ever been replaced. I am not sure if the starter or the battery are the problem so here's what I am planning on doing when I get home today and I'd like your feedback:

    1) Put volt meter on battery to see the battery draw (per Bentley's)
    To do this, I'll have to disconnect the negative terminal - Will disconnecting the negative terminal wipe out any settings, like radio? I know a complete disconnect requires the radio security code - not sure about just negative.How do you all keep power pumping into the computer/systems when you do a battery disconnect?

    2) If battery reads OK, install new starter. Any product recommendations, tips, gotchas?

    Am I missing anything?

    Thanks
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    az3579

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    I'm not all too much of a tech, but I think if it cranks, the starter would be OK... (anyone confirm this?)



    If you disconnect just the negative, that would be breaking the circuit and is the same thing as if nothing was connected to it. Yes, you will need to reset the on board computer's clock and date, and yes, you will need your anti-theft radio's code (if you have one of these radios) to unlock it.
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    mooseheadm5

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    If the starter does not engage (i.e. the starter spins fast but the motor does not spin at all) then it is the starter 99% of the time. If you put a voltmeter on the battery and read over 12.5 volts, then crank the car with the key and read over 10ish volts during cranking, the battery is pretty OK and you do not have to disconnect it. You can't do a starter draw test with the battery disconnected anyway, unless you have one hell of an ammeter, and you do not. Just touch the red voltmeter wire to the + side and the black to the - side, set it to 20 volts DC (or just DC volts if it autoranges) and go for it.
    Now if you mean that the engine cranks over but does not fire, you have other problems.

    slinky66 guest

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    I think I can rule out the starter as the problem because the starter is turning the engine - I think I can rule out crank position sensor although I'm not certain if the "Check Engine" light would illuminate with the key in start mode but without turning over. Does anyone know?

    Seems like that leaves the battery then - Should I be checking anything else? My car has always ran tip top up until today so this seems like maybe a battery that was on the fringe or some other component just simply failed.

    Jeron guest

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    Always start with the battery. If the battery checks out move to fuel system then crank pos sensor.
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    mooseheadm5

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    If the starter turns the engine at normal speed, the battery is fine. If it cranks slowly, charge or replace and retest. You may not get a check engine light if something died overnight. Also, DO NOT disconnect your battery with the key in the ignition or you face damaging the EWS system. Once you determine if hte battery is good, you need to find out what you lack- fuel, spark, or compression. Usually on those cars, compression is not the issue. It could be fuel or spark. If you can run the car on carb cleaner (sprayed into the intake while cranking AT YOUR OWN RISK,) you have spark and no fuel. If you cannot, you are missing spark and possilbly also fuel. In either case it could be a relay or computer related. Check all fuses, then move on to testing fuel pump output by jumping out hte fuel pump relay. If you hear nothing, then it is probably the fuel pump. Anything else requires further diagnostic, and you may not have the capability to go much further than that.

    Jeron guest

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    All of the above is great and in very good detail. In the end, if you get past the battery and fuel and you are considering taking it to a mechanic buy a Crank Pos Sensor first.
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    mooseheadm5

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    Or since it is a 95, if you feel froggy, I can tell you how to test your sensor, but you will get your hands dirty and you need a digital multimeter and a helper.

    slinky66 guest

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    Sure! Thanks. I have a digital multimeter and I do not mind getting my hands dirty. How do I do it?
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    mooseheadm5

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    You have to locate the plug for it under the intake, which may require removing the airbox. There are some similar plugs there so it may help to just trace the wire back from the sensor. You need to unplug it and ohm the terminals, but damned if I can remember if it is 1 to 3 or 1 to 2 or 2 to 3 (I am not at the shop today.) Just test all pins to all other pins and lemme know what you find. If you find no continuity for any pins to any other pins, then your crank sensor is bad. If you find continuity, you need to set your meter to AC volts and read the voltage on those pins while cranking. Should increase with RPM.

    slinky66 guest

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    Greetings Paul,

    So I took your advice and tested the throttle position terminals as follows:

    1 and ground in harness conductor; ignition on: multimeter set to 20 VDC. no reading
    1 and 3; ignition off: multimeter set to 20k ohms. got a reading of 4.38k
    1 and 2; throttle plate rotated from idle to full; don't know how to do this -

    Interestingly, after I was done testing and put the harness conductor back, she started up. I also tried starting her before I did the tests and she would not turn over so does that suggest a bad sensor? bad harness? are they two distinct parts?

    Thanks again

    slinky66 guest

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    Just went out to the garage and noticed something pretty telling. The engine would idle for about twenty seconds, the rpms would rise and then it would almost die out. Idled some more rpms would raise and then she died out. Can someone help me put the pieces together? Sure sounds like the throttle position sensor
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    mooseheadm5

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    Uhh, hmm. You were supposed to be testing the crank position sensor, not the throttle position sensor. The TPS should not cause the car to not run, but I guess it is possible. At any rate, Have you tried to run the car on carb cleaner sprayed into the intake? Have you tried opening up the throttle when it is running to see if it dies out or if it revs up? I'll be on for a while, lemme know what happens when you do these things. Your problem definitely sounds intermittent electrical, which can be the crank position sensor. Any check engine light yet?

    slinky66 guest

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    Fuses look fine; Ugh, no carb cleaner! I think I am going to look at the fuel pump next. You mentioned jumping out the fuel pump relay and listening for something. Can you elaborate a little? Bentley's has no mention of trouble shooting relays Thanks
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    mooseheadm5

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    To jump out relay, first find it in the ebox under the hood. It has a big fat red/white wire and a big green/purple wire, and a couple of other wires going into it. If you jump the red/white wire to the green/purple wire that should power up the fuel pump. Oh, just to add to your fun, there are two relays that fit this profile, but one is the O2 sensor heater relay, which has smaller wires. You will hear it. I did have a car the other week that would run intermittently, then it finally died. It turned out to be a bad fuel pump. It was a PITA to find because it kept starting unexpectedly. Once it finally would not start again and we heard no fuel pump after jumping the relay, we added fuel with an external pump, that clinched it. It ran great. The electrical stuff is really hard to trace.

    slinky66 guest

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    Great thanks. I will attack this on Monday. So when I jump it out, if I do not hear the pump engaging I should replace? What fuel pump would you reccomend? Manufacturer? Model? Thanks
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    mooseheadm5

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    I don't like throwing parts at something until I have a definitive answer. Normally, I would check fuel pressure while jumping out the relay becaues even if it runs, it may not make the pressure. The pump is not cheap, nor is it easy to replace because it lives in the tank and you have to immerse your hand into whatever gas is in the tank to unclip it. If you do not get it back in right you can have problems. Bosch only pumps for me, but I had to cut and splice in the last one because it comes as a bare pump with different terminals. Don't know your skill level, but you may need to punt on this one.

    Jeron guest

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    Paul, you are very patient, kudos.

    Slink66m, take minute and go back a reread the whole thread and take stock of the problem you seem to be jumping from item to item and not getting reaching conclusions. Go buy a $2 can of carb cleaner, it can eliminate a whole group of possibilities, pun intended.

    slinky66 guest

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    Starter or battery

    I really appreciate all of the great advice and guidance from the group! I spent the last several hours troubleshooting my car and here's what I found:

    Sprayed carb cleaner into intake manifold while my assistant cranked with accelerator depressed
    Car cranks but would not start

    Jumped out fuel pump relay
    Heard pump running - Car cranks but would not start

    Checked fuses]
    Fuse #25 blown (auxiliary fan) Does not seem responsible for the starting problem

    Checked all 6 ignition coil harness connectors
    terminal 15 (+) and terminal 1 (ground)
    My multimeter would only read with ohm range set at 200M I was getting readings of -70.06 ohms; the acceptable resistance range is 0.4 - 0.8 ohms. That -70 ohms does not seem to convert to the acceptable range.

    Is there anything else I can try? I would love to fix this myself!

    Thanks in advance
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    mooseheadm5

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    Umm, you are testing the resistance in the computer. You need to test the resistance of the coil pack if that is your aim. You are all over the place here. In order to fix it you need to follow a logical path. I don't know why you were testing the coil harness connectors either. Don't recall mentioning that you should. If it will not start on carb cleaner, you have no spark. Next logical step is to check for injection pulse. If it has injection pulse but no spark, probably the ECU or multiple bad coil packs. If no injection pulse or spark, check crank position sensor like I said. If that tests bad, replace it. If it tests good, there is the possibility that you have either a bad ECU or are having an EWS problem, neither of which you can fix yourself. Swapping the ECU or testing the EWS requires equipment you can't get.

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