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Thread: M20 starter into M10?

  1. #1
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    M20 starter into M10?

    Ok, so I have a almost new starter laying around and I stumbled onto a thread dealing with dropping in an E30 starter into an M10, which fits perfectly. The issue I'm having is that my son's 320 is a 7/79 and it has a totally different wiring then post 80....right?

    We dropped it in and she cranks really good, no issues there, but now she wont fire! hahahahahah

    So if I dont get any answers here in the next couple days, we will have to just put a 14 lb M10 starter back in bummer

    Basically it appears that she is not firing....can smell the fuel and hear the pump going sooooo
    My build thread M20 than S50 into 320i: http://forums.bimmerforums.com/forum...0#post23442810

  2. #2
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    See if it fires when you put a jumper wire between the batt "+" and the coil "+". Don't run it for more than 30-60 seconds this way, it's just a test.

    If it does fire, there may be a problem with the ignition resistor bypass wire, which connects between the starter solenoid's spade connector and the coil "+". Or maybe the M20 solenoid does not have that 2nd spade connector?

    Also, if the tailpipe smell like gasoline, disconnect the wires to the cold start injector so it will stop flooding the engine.

    Let us know what happens.
    I'm signing off for the night, but that should give you something to check for now
    Last edited by epmedia; 05-27-2013 at 03:25 AM.
    Tbd

  3. #3
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    Thnx man.... I'll post a pic of the spades on that starter. Basically what happened was, the starter that he had in, the huge 14 pounder, was making grinding noises. Well, when we took it out, I noticed #1 that the starter appeared to be new and #2, a screw that holds the arm that throws the gear out and engages the flywheel. So that was the culprit!

    I remember comparing the spades on the back of the solenoid and I swore the layout seemed same? Also, the wiring that you're talking about has been replaced by PO unknow when? It's definitely a BMW replacement or recall?

    Personally I would really love to use that M20 starter with this M10, so much stronger, smaller and most importantly lighter!

    Day off tomorrow, so I'll run the wire per your instructions
    My build thread M20 than S50 into 320i: http://forums.bimmerforums.com/forum...0#post23442810

  4. #4
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    The pinion gear is different between M10 and M20 starters, so I'm not sure how good the engagement with the flywheel ring gear is going to be. Wiring shouldn't be an issue though, since the only connections are for the +12V and the solenoid?

  5. #5
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    ski, with a points ignition you need 3 connections at the starter.

    post 30 - battery V+
    post 50 - black wire from key switch, cold start injector, thermo time switch, unloader relay
    post 16 - black/red wire to coil V+ terminal

    a points ignition can not handle the 14v the alternator is supplying so a ballest wire with a resistance of 0.9 ohm is used to feed power to the coil's V+.

    when the starter is activated battery voltage is supplied from starter post 30, out of the solenoid's post 16, through the bk/rd wire to coil post V+. this temporarily supplies the coil with 12.xx v for assisted starting.

    this is why Robert said to try a wire from battery V+ to coil V+ while cranking, you're probably missing that connection or have it wired to the wrong terminal at the starter.
    Tom D

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  6. #6
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    Quote Originally Posted by m20powered View Post
    The pinion gear is different between M10 and M20 starters, so I'm not sure how good the engagement with the flywheel ring gear is going to be. Wiring shouldn't be an issue though, since the only connections are for the +12V and the solenoid?
    Tell that to Jester

    http://forums.bimmerforums.com/forum...ht=m20+starter

    - - - Updated - - -

    Quote Originally Posted by Tom D View Post
    ski, with a points ignition you need 3 connections at the starter.

    post 30 - battery V+
    post 50 - black wire from key switch, cold start injector, thermo time switch, unloader relay
    post 16 - black/red wire to coil V+ terminal

    a points ignition can not handle the 14v the alternator is supplying so a ballest wire with a resistance of 0.9 ohm is used to feed power to the coil's V+.

    when the starter is activated battery voltage is supplied from starter post 30, out of the solenoid's post 16, through the bk/rd wire to coil post V+. this temporarily supplies the coil with 12.xx v for assisted starting.

    this is why Robert said to try a wire from battery V+ to coil V+ while cranking, you're probably missing that connection or have it wired to the wrong terminal at the starter.
    Gotcha.....

    I wonder if there is more to this then me throwing in the M20 starter? The other night we went for a spin....3 E21's and we stopped to fill up....Devin's wouldn't start as is right now? I drove home ( a mile away) picked up some wire, couple wrenches and my handy ohm meter and just when I was about to leave, he called and said the car started and they were on the way! Hmmmmmmmm.......

    I'm gonna throw some pics on here and you guys tell me what ya think? The only difference I've found so far was that the + trigger wire from the ignition sits opposite from what the M10 starter got. M10 is on top when you look down and the M20 spade is on the bottom....

    I'll show ya pics....

    - - - Updated - - -

    Quote Originally Posted by epmedia View Post
    See if it fires when you put a jumper wire between the batt "+" and the coil "+". Don't run it for more than 30-60 seconds this way, it's just a test.

    If it does fire, there may be a problem with the ignition resistor bypass wire, which connects between the starter solenoid's spade connector and the coil "+". Or maybe the M20 solenoid does not have that 2nd spade connector?

    Also, if the tailpipe smell like gasoline, disconnect the wires to the cold start injector so it will stop flooding the engine.

    Let us know what happens.
    I'm signing off for the night, but that should give you something to check for now

    Hey Robert and Tom, should I run to the Radio Shack and just get a 0.9 Ohm resistor and then try to do the + batt to + coil connection test??? I really don't feel like frying up what appears to be a new coil today?!?!?! Even if it's a memorial day or not....it's not the BBQ I am looking for!! hahahahhah

    - - - Updated - - -

    Ok....

    Couple pics with the iphone since my camera wouldn't fit. Also, keep in mind, me using house connectors is not my idea of a good practice, so what you see is PO doing, which will be fixed! I'm just trying to figure out the norms and workables, then I'll fix everything with solder and heatshrink....

    I presume that wire that the big yellow house connector is, is the wire that goes back to the coil??????? And why is there 2 bro/red wires connected to it? I dontttttt knowwww!!!!!????? OMG, this PO or his mech had just no clue!




    and that's the view of the coil connectors


    - - - Updated - - -

    original M10 starter solenoid view:


    Here are the wires from the harness


    Why there are 3 blk wires going to the starter spade like this? I made that Blk/Yel extension for temprary purposes only...that's the original E30 wire that already was connected to the starter...
    Last edited by lasvegascop; 05-27-2013 at 03:27 PM.
    My build thread M20 than S50 into 320i: http://forums.bimmerforums.com/forum...0#post23442810

  7. #7
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    the three black wires all connect together at the solenoid. key switch, cold start injector/thermo time switch, and the unloader relay.

    - - - Updated - - -

    the black/red wire does indeed go to the coil V+. it looks to be like they had a female spade of the right size but the wrong colors and just spliced it in.

    the black/red wire should only see battery voltage when the starter is being cranked, you can verify that with a multimeter. with the key on and the starter at rest, the terminal without the bk/rd wire attached should see no voltage, the wire however will see whatever V+ the resister wire has at the coil's v+.
    Tom D

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  8. #8
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    Do you have the wiring diagram? Here is a pdf version of the '77 wiring diagram:

    http://www.jtresto.com/e21/ETM_1977.pdf

    I see the coil + has two wires going to it. Green goes through the 0.9 ohm ballast. There is also a black/red that goes to the coil + from the starter solenoid, and that one does not pass through the ballast. So that would be for spark while cranking and would give you more voltage because of not going through the ballast resistor.

    Next time this vehicle does not start, the first thing I would do would be put the voltmeter on the coil + with the other meter lead going to ground just to make sure the coil is getting voltage.

  9. #9
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    looking at the heat damage to the coil wire connection as well as the ballast wire, I would dig down the wire harness a ways for any additional damage or fusing of the two wires
    Tom D

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  10. #10
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    Quote Originally Posted by Tom D View Post
    looking at the heat damage to the coil wire connection as well as the ballast wire, I would dig down the wire harness a ways for any additional damage or fusing of the two wires
    Ohh geez Tom...you're scaring me now, but on the bright side...it's a 79 and it has nothing compared to re-wiring or slicing in an M20!!!! I will confirm and verify that they go thru with the ohm meter and that they're not fused as you suggested brother.....

    Right this second, I am working on Amir's fan shroud....kid needs it badly....he's got a new rad, new water pump, new improved fan with a clutch and it still creeps up to 3/4 mark....but this shroud I'm building for him will definitely solve the Las Vegas heat issue!!!

    So as soon as my kid gets off work today, we will swap the starters again and see what happens.....after I recheck all the wiring....

    I'll keep the thread posted

    - - - Updated - - -

    Quote Originally Posted by okieflats View Post
    Do you have the wiring diagram? Here is a pdf version of the '77 wiring diagram:

    http://www.jtresto.com/e21/ETM_1977.pdf

    I see the coil + has two wires going to it. Green goes through the 0.9 ohm ballast. There is also a black/red that goes to the coil + from the starter solenoid, and that one does not pass through the ballast. So that would be for spark while cranking and would give you more voltage because of not going through the ballast resistor.

    Next time this vehicle does not start, the first thing I would do would be put the voltmeter on the coil + with the other meter lead going to ground just to make sure the coil is getting voltage.
    Thank you sooo much for this wiring schematic......if you have anything else please PM me or better yet, post it here so everyone can use, search it or just look at it.
    Personally I am NOT a huge fan of the FAQ because it's very difficult to find things in a hurry hahahahahah After all, we are men and we like to see things NOW!

    I've found tons of info thru threads and guys that like to chime in that have first hand knowledge ie Tom and Robert above. I'll take that anytime over some FAQ ...live help is priceless!!!

    - - - Updated - - -

    Quote Originally Posted by Tom D View Post
    the three black wires all connect together at the solenoid. key switch, cold start injector/thermo time switch, and the unloader relay.

    - - - Updated - - -

    the black/red wire does indeed go to the coil V+. it looks to be like they had a female spade of the right size but the wrong colors and just spliced it in.

    the black/red wire should only see battery voltage when the starter is being cranked, you can verify that with a multimeter. with the key on and the starter at rest, the terminal without the bk/rd wire attached should see no voltage, the wire however will see whatever V+ the resister wire has at the coil's v+.
    Ok so that's good to hear....All I have to do is clean it up a bit...sweet!!!

    - - - Updated - - -

    Quote Originally Posted by m20powered View Post
    The pinion gear is different between M10 and M20 starters, so I'm not sure how good the engagement with the flywheel ring gear is going to be. Wiring shouldn't be an issue though, since the only connections are for the +12V and the solenoid?
    For argument sake, which you might be right...when I pull the other starter out, I'll take a micrometer and measure the teeth on the ring gear.....

    Thank you for chiming in brother....I will post the findings too....
    My build thread M20 than S50 into 320i: http://forums.bimmerforums.com/forum...0#post23442810

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    Just to be certain there's not an additional problem, Have you verified spark with and without the wire jumped between battery and coil?

    As Tom pointed out - that resistor wire may be making a mess in the harness. The condition of this wire gets worse and worse on it's way down to the connection at the start-run bus.

    Here's a pic of a bad resistor wire from one of my '78s:
    You may see a bulge in the harness where it's crimped to the start-run bus, near the starter motor.

    click to enlarge
    ign-resistor-wire-bad.jpg

    I would not use a resistor from Radio Shack.

    If you want to rig your own ballast/resistor, go to the auto store and get a ignition ballast resistor with spade terminals for an old Chevy (ie: '63 impala, or '57 belair, etc.).

    OR ignition ballast resistor wire for an old Ford, (ie: '65 Mustang).
    Last edited by epmedia; 04-10-2015 at 03:25 PM.
    Tbd

  12. #12
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    Quote Originally Posted by epmedia View Post
    Just to be certain there's not an additional problem, Have you verified spark with and without the wire jumped between battery and coil?

    As Tom pointed out - that resistor wire may be making a mess in the harness. The condition of this wire gets worse and worse on it's way down to the connection at the start-run bus.

    Here's a pic of a bad resistor wire from one of my '78s:
    You may see a bulge in the harness where it's crimped to the start-run bus, near the starter motor.



    I would not use a resistor from Radio Shack.

    If you want to rig your own ballast/resistor, go to the auto store and get a ignition ballast resistor with spade terminals for an old Chevy (ie: '63 impala, or '57 belair, etc.).



    OR ignition ballast resistor wire for an old Ford, (ie: '65 Mustang).


    NICE!!!!!!! I think on the safe side, I will go that route
    My build thread M20 than S50 into 320i: http://forums.bimmerforums.com/forum...0#post23442810

  13. #13
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    Robert, isn't it nice to have a cop in our pockets?
    Tom D

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  14. #14
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    Quote Originally Posted by Tom D View Post
    Robert, isn't it nice to have a cop in our pockets?
    hahahahahhahaha....you do!!!!

    - - - Updated - - -

    Update!

    Son came home from work...we took the M20 starter out and as I promised to "M20powered" I did some measurements.

    So here it is:

    Here are the two next to each other....the way that matters hahahaha...showing the gears. As you can see, the M20 gear is a tad smaller and that's on the right


    I measured the M10 gear and I got exactly 9mm from hump to hump


    then I measured the M20 gear and I got exactly 8mm


    Compared the two and the difference is this:


    Sooooooooooooooo in conclusion.... I thought because of the thread started by Jester in 2009 that the gearing would work....in short, M20powered was correct. Full credits go to him. Also not only the gearing is off a bit, which by the way you can tell when it's starting.....the electronics are screwed up too!!!

    Basically, after the missing bolt in the M10 starter was replaced, we re-installed it and she fired after a few tries (she was flooded from last night!) Soooooo, maybe you can use the M20 starter on a post 80 320i, but 77-79 NOT so much....

    Again, thank you again for all that threw in words of wisdom....

    ohhh yeah Tom....the coil wire that runs from the starter? I measured it, cleaned it and plugged back in....there wasn't any cross over to the others so I think we are good on the melting. Everything that was brought up in this thread helped me and I hope it helps someone else in the future.....

    Thnx brothers
    Last edited by lasvegascop; 05-27-2013 at 10:52 PM.
    My build thread M20 than S50 into 320i: http://forums.bimmerforums.com/forum...0#post23442810

  15. #15
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    ski, can you change the nose and the drive gear to the M20 starter?
    Tom D

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  16. #16
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    Quote Originally Posted by Tom D View Post
    Robert, isn't it nice to have a cop in our pockets?
    You betcha. lol

    Fun aside, Ski reminds me of the local law (Sheriffs and CHP) I grew up with in my town in the '80s. Really cool dudes. By the book, while maintaining a sweet heart

    I'm not sure how a smaller diameter gear meshes up, accounting for offset and all. But the 2nd spade terminal for the resistor bypass wire is throwing me off - maybe the internal contacts were omitted or some other strangeness happening inside there. I know it's a moot point now, but I'm once again curios of what's different inside that M20 starter solenoid regarding that 2nd spade terminal for the resistor bypass wire.

    Oh - the wire that can possibly be messing up the harness is the "resistor" wire from the start-run bus, not the "resistor bypass" wire from the starter solenoid.
    Last edited by epmedia; 05-28-2013 at 01:26 AM.
    Tbd

  17. #17
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    Quote Originally Posted by epmedia View Post

    Fun aside, Ski reminds me of the local law (Sheriffs and CHP) I grew up with in my town in the '80s. Really cool dudes. By the book, while maintaining a sweet heart
    I just got back from bishop, ca. where I stayed with an ex deputy sheriff from silverpeak/tonopah nv. great guy, had lots of good stories. it was also mule days in bishop, I never saw so many women's asses wrapped in tight blue jeans in my life, it was a sight to behold.
    Tom D

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    Sounds like fun Tom

    I wonder if Ski recalls my story awhile back about when I got frisked by a female sheriff for tinted windows on the '78. She was pretty cool too. lol

    Edit: if the M10 starter motor seems sluggish, a common part that wears out and is easy to replace while the starter motor is installed, is the bushing #14 behind the end cover #15.
    My OE starter has a rubber bushing around #14 and I just used a piece of rubber hose to replace the worn rubber (not shown). Just something else to ponder on if the starter motor is sluggish. #14 is still avail for just a few bucks.

    Last edited by epmedia; 05-28-2013 at 04:02 AM.
    Tbd

  19. #19
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    Quote Originally Posted by Tom D View Post
    I just got back from bishop, ca. where I stayed with an ex deputy sheriff from silverpeak/tonopah nv. great guy, had lots of good stories. it was also mule days in bishop, I never saw so many women's asses wrapped in tight blue jeans in my life, it was a sight to behold.
    Tom, Tom, Tom? You know the tiles here.... No pics? It never happened?!?????!! Haha!!!!!

    - - - Updated - - -

    Quote Originally Posted by epmedia View Post
    Sounds like fun Tom

    I wonder if Ski recalls my story awhile back about when I got frisked by a female sheriff for tinted windows on the '78. She was pretty cool too. lol

    Edit: if the M10 starter motor seems sluggish, a common part that wears out and is easy to replace while the starter motor is installed, is the bushing #14 behind the end cover #15.
    My OE starter has a rubber bushing around #14 and I just used a piece of rubber hose to replace the worn rubber (not shown). Just something else to ponder on if the starter motor is sluggish. #14 is still avail for just a few bucks.
    Yeah.. Our starter wasn't sluggish (but that's good to know about that bushing) but it had a missing bolt. Don't know what it's called but basically it wouldn't allow the solenoid to retract the gear back in so it was grinding like hell!
    Like I keep telling my son, it's the little things that add up over time. But again, for $500 who to argue?

    Also, the 2.0 has a lot of power! Omg... That's thing has no issues at all keeping up with my M20?!?!?!? Must be of the weight cause I know I'm making very close to 190-200hp!

    - - - Updated - - -

    Quote Originally Posted by epmedia View Post
    You betcha. lol

    Fun aside, Ski reminds me of the local law (Sheriffs and CHP) I grew up with in my town in the '80s. Really cool dudes. By the book, while maintaining a sweet heart

    I'm not sure how a smaller diameter gear meshes up, accounting for offset and all. But the 2nd spade terminal for the resistor bypass wire is throwing me off - maybe the internal contacts were omitted or some other strangeness happening inside there. I know it's a moot point now, but I'm once again curios of what's different inside that M20 starter solenoid regarding that 2nd spade terminal for the resistor bypass wire.

    Oh - the wire that can possibly be messing up the harness is the "resistor" wire from the start-run bus, not the "resistor bypass" wire from the starter solenoid.
    Yeah I know.... I was very hopeful and excited about the M20 starter too bummer. But as Tom stated, the gear can always be swapped, which I thought it could be (never done it but still my mind was working on that haha) but then the electricals inside screw everything up.

    I wonder if you could swap the solenoid???????????????
    My build thread M20 than S50 into 320i: http://forums.bimmerforums.com/forum...0#post23442810

  20. #20
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    Just for your info pretty sure that CJ and the other guys have used the E30 M3 as a starter replacement...for the M10 motors.
    "..Horsepower is a measure of work done over time, or the rate at which work is done."




    http://www.cardomain.com/ride/579694/1


  21. #21
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    Quote Originally Posted by jjgbmw323 View Post
    Just for your info pretty sure that CJ and the other guys have used the E30 M3 as a starter replacement...for the M10 motors.
    Yup.... The issue I'm having is that the 79 has a extra wire that's hooked up to the starter that's connected to the coil. The M20/E30 starter wouldn't make her start

    So its a huge possibility that post 80 year cars have no problem with that mod due to having an ECU???

    I just donno man.... If someone has done it on a pre 80 and is willing to tell/show with pics, I might take another crack at it haha. It is nice to have a smaller, lighter, more powerful starter in there

    On other hand, after the install, has something else happened that she wouldn't start? Coincidence? Big possibility! We've had her for about a month, she was a non runner so as of right now, due to so many unknowns, I must call her "unreliable" still.....so that's where we sit.

    After she spends some more time driving around, change temps, altitude maybe even more mileage...then she'll be upgraded to reliable again
    Last edited by lasvegascop; 05-28-2013 at 02:37 PM.
    My build thread M20 than S50 into 320i: http://forums.bimmerforums.com/forum...0#post23442810

  22. #22
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    Not sure if the son weighs as much as dad, probably not if he is marine material, so weight savings on starter is really a non factor. Stay off those donuts Vegas.

  23. #23
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    Quote Originally Posted by gsumzzz View Post
    Not sure if the son weighs as much as dad, probably not if he is marine material, so weight savings on starter is really a non factor. Stay off those donuts Vegas.
    Haha ... Funny guy
    My build thread M20 than S50 into 320i: http://forums.bimmerforums.com/forum...0#post23442810

  24. #24
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    So gents.....here is a new kicker with my son's 79.

    She won't start, well I should say, start again in 24 HR period. She will start and once you shut her off it's a No go again!

    We have changed the cap, rotor, plugs, coil, wires..... No go.
    At first I thought maybe it was the fd but that's fine, we get fuel squirting out of the injectors. I pulled the wire and put a spare plug in it and grounded it to the header....we are not getting any spark!

    So I pulled the coil wire out that goes into the distributor and she's sparking like hell.

    I don't know what to do next? I even changed temp ignition harness and she crankshaft with that just like before.....just not getting any fire.
    I was thinking about just replacing the resistor wire all together and see what happens? It's .9 ohms right? Any words of wisdom on this? Really need your assistance, this thing is really pissing me off, it's not like I've never worked on a car or anything haha
    Last edited by lasvegascop; 04-08-2015 at 05:41 AM.
    My build thread M20 than S50 into 320i: http://forums.bimmerforums.com/forum...0#post23442810

  25. #25
    Join Date
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    sold 78 BMW 320i
    Quote Originally Posted by lasvegascop View Post
    So gents.....here is a new kicker with my son's 79.

    She won't start, well I should say, start again in 24 HR period. She will start and once you shut her off it's a No go again!

    We have changed the cap, rotor, plugs, coil, wires..... No go.
    At first I thought maybe it was the fd but that's fine, we get fuel squirting out of the injectors. I pulled the wire and put a spare plug in it and grounded it to the header....we are not getting any spark!

    So I pulled the coil wire out that goes into the distributor and she's sparking like hell.

    I don't know what to do next? I even changed temp ignition harness and she crankshaft with that just like before.....just not getting any fire.
    I was thinking about just replacing the resistor wire all together and see what happens? It's .9 ohms right? Any words of wisdom on this? Really need your assistance, thus thing is really pissing me off, it's not like I've never worked on a car or anything haha
    If understand correctly:
    It sparks good out the coil, but no spark to the plugs?

    Make sure the ignition points are not pitted and are gapped properly to .016". If the points lost their gap, you may need to polish the points cam. Also make sure the points wire is not rubbing on anything, and make sure the condenser has a good connection. If the points gap was lost, you also want to replace he points. Don't forget to put a little 'points grease' on the points cam. Also make sure the rotor is in it's slot and seated.

    You may also have to check the "+" voltage at the ignition coil. It should be atleast 9.0V while turning the starter motor and atleast 11V with the key in RUN position. Also, remember there is a ignition resistor bypass wire that connects between the starter motor solenoid and ignition coil "+".

    Related to the OE ignition ballasts wire:
    If it's original, I'm certain it needs to be replaced. You can use either of the two mentioned in post #11. You would have to cut away the wire wraps to get to the cold soldier joint near the starter motor and then soldier in your new wire.

    *Does the engine try to fire only while turning the starter motor? If so, the OE ballast wire is probably fried, or there may be issues with the ignition switch.

    *If the points condenser is old, replace it if the ignition points look bad.
    *Note: a bad condenser will usually make blue/black dots on the point contacts.

    I hope that helps...
    Tbd

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