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Thread: 1972 BMW 2002 Missing/Dying issue

  1. #1
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    1972 BMW 2002

    1972 BMW 2002 Missing/Dying issue

    I'm wondering if anyone has advice about an issue I am having with my 1972 BMW 2002. The car is almost completely stock. It has a Weber 32/36 carburetor. It was running fine until it began having an issue where it would run for about 20 minutes and then start to miss, stutter, and ultimately die. My dad is somewhat of a BMW expert (raced/owned 2002s for years in the SCCA), and has changed the distributor and coil to electronic, disconnected the vapor recovery system to vent the tank, changed the fuel pump, alternator, done a valve adjustment, put new spark plugs and spark plug wires, and performed a general tune-up. Still, the issue persists! It has been a long time, and he still can't figure out what the problem is. Anyone have any ideas?

    Thanks in advance!

  2. #2
    MauiM3Mania's Avatar
    MauiM3Mania is offline Observer/Master Skeptic Moderator
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    Is it running out of gas? What do the recent plugs look like?

    Copied your post to the 2002 sub-forum from the General Mechanical sub.
    04M3 TiAg 69k slick-top 3 pedal
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  3. #3
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    Since your Dad has replaced almost everything else, why not temporarily bold on the super simple stock one barrel carb and intake manifold and see if the problem disappears.

    This is obviously not the best way to diagnose problems, but those carbs and manifolds are so readily available used that it seems like a quick way to eliminate the Weber that's on there right now as the source of the problem. Also, since your Dad has raced and owned 2002's for years, if he's anything like me, he must have a number of those lying around.

    If you don't have one of those set ups and you think it might be worth try, I could lend you one for free if you pay the shipping both ways.

    Regards, Maurice.

  4. #4
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    Sounds like fuel starvation or related issue to me. Is there a clogged fuel filter you can locate/change? Is the pump itself faulty? Maybe a dirty carb jet (try carb cleaner). Or the choke is faulty (stays on past warm up)?

    The 32/36 is a solid carb, many have swapped to it. I wouldn’t think that’s the source of your problem unless it’s new or recently re-jetted, esp. if it ran fine before.

    20 mins means it’s warmed up when it starts to falter. Hmmmm. Are you seeing any overheating?

    Electronic distributor - I assume you mean like a Pertronix ignitor instead of points?

    How’s your charging system? Could it be running off the battery and then just dies out? Could coil be bad (once it gets hot)?

    Tom

  5. #5
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    '72 BMW 2002,197 02002
    Hello, I,m Tom, Clewis7's car is my problem! 32/36 weber is Redline jetted for 2002 weber, bome siock. Checked float level immediately after stalling-it was fine. Installed good used distirutor with Pertronix trigger new wires and new blaster coil. No overheating issues. Fuel filter new carb clean, jets clear. New alternator and new fuel pump, didn't help! Problem started with original distributor points, coil fuel pump and original alternator. New wires, spark plugs air filter, new manifold to servo hose, valve adjustment etc. No vacumn leaks! Runs strong for 20-25 minutes, rough for about 5 minutes, then dies. After restart, it only lasts about 10 or 15 minutes before dying again! Fuels lines are clear, no obstruction. I'm glad my ITB SCCA car never had such issues!
    Last edited by delboto; 09-20-2019 at 12:09 AM.

  6. #6
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    The failure mode in both these cases indicates it’s a thermal problem of some kind. It could be fuel-related or electrical, but more likely the latter.

    20 mins seems too long to a fuel issue. But if it’s fuel, it could be air entering the lines somewhere, getting hot leading to a vapor-lock condition (fuel pickup, pump, pin-hole leak in fuel line, etc) or proper fuel delivery failing once it’s warm (and off choke).

    For electrical, maybe the coil or the Pertronix overheating and shutting down - or the ambient heat is mechanically opening a bad electrical connection (wires, grounds, etc). If your tach jumps about just before it starts to fail, it’s more likely to be on the electrical side. When it dies, pull a plug wire and check you still have spark.

  7. #7
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    No vapor lock, no jump from the tach needle, I would think the brand new Pertronix unit or the coil is the problem, but the problem started just the same with points ignition and Bosch blue coil, of course, it has new plugs, wires, rotor and distributor cap, new alternator and new fuel pump which were apparently unneeded!? The fuel supply is comes through the plastic line emerging from the firewall, and the return line uses the steel line under the left side of the car (that I have always felt is the fuel supply line!) This is a 1972 California smog car and the setup seems stock!?. Previous to this the car ran strongly for many years with this setup!

  8. #8
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    Do does it still have spark to all plugs when it dies? (Pull wire and short to block test each cyl).
    When it becomes rough, do you have to fuss with the throttle to keep it going?
    How long til it can restart? Is the engine still hot? Has the thermostat opened by then?

    Pertronix have been known to be bad or go bad, and can overheat and fail like this - but since you had problem prior maybe it’s not that. Swap in a set of points and see. Coils can also fail with overheating.

    If you had a pinhole leak in a fuel line, it could pull in air which can cause a vapor lock after air builds up and gets hotter, leading to fuel starvation. When it dies do you still have/see fuel at the carb?
    Is your return line working? Is the carb off-choke before it dies?

    How’s the battery and it’s charging? Steady voltage throughout, from running fine to rough?

    There’s many places where wire/electrical connections can be fine and have continuity when cold, but when it gets hot move a bit to become unconnected (my mechanical failure type electrics comment above).

    I don’t know much about the smog equipment (ripped all mine out) and if any of that could be culprit. I do know it makes the engine run hotter.

  9. #9
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    '72 BMW 2002,197 02002
    I've never checked the spark because it restarts immediately! So spark is there! I will check if gas flows through the return line. I wonder why it needs one, since my two older 2002's and my '69 MGB have none, just direct feed to the carbs! Choke is wide open when it dies. Weber has proper fuel level as it dies! Its cold near San Francisco so I doubt vapor lock, Bad random electrical connection is a scary thought! It never runs hot around here, ambient temperature usually 50 to 60 degrees F. Wish I could remove smog but that's not an option here in the Peoples Republic of California! Tom
    Last edited by delboto; 09-19-2019 at 01:19 PM.

  10. #10
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    '72 BMW 2002,197 02002
    I have noticed that the inner fender mounted coil is very hot during running, a bit odd?

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