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Thread: Spark plug

  1. #1
    Join Date
    Oct 2005
    Location
    Markham, Ontario
    Posts
    57

    Default Spark plug

    Ok I need some help with this one.

    Spark plug #5 on the spark plug wire and 2nd on from the fire wall

    I have 1 spark plug not firing...I disconnected the spark plug wire and the engine had no reaction. I turned the engine off and I found the spark plug wet with gas. The rest of the plugs are firing.

    I changed the spark plug wire with a spare one and I have no change didn't make a difference. I changed the the coil aswell no change.

    would it be just a faulty spark plug?

    will the TPS have any affect on the spark plug firing.

    I have fuel
    I have air
    just short 1 plug for firing

    1989 m20

    Thanks


    Later on that day...........................................

    Put a new plug in, I swaped out the rotor and cap and still have the same problem. that one plark plug not firing.

    -changed the spark plug
    -changed the spark plug wire
    -changed the rotor
    -changed the cap

    still plug number 5 (2nd from the fire wall) not firing

    Question? will the TPS or the AFM send signals to the computer not to fire that plug?

    I have a spare AFM and throttle body that I will try tomorrow.

    I did change the CPS 2 twice and no change in the engine

    I have all new hoses

    What about ICV will that send signals to the computer?

    Thanks
    1989 BMW 525 - M20--119,000.00-Original KM - now 5-speed


  2. #2
    Join Date
    Jan 2004
    Posts
    4,148

    Default

    Do a compression test on that cylinder.... no compression=no combustion=wet spark plug.


  3. #3
    Join Date
    Jan 2004
    Posts
    4,148

    Default

    No , the tps and afm will not single out that one cylinder and the computer won't shut it down either.. not until much later, obdII cars have that capability on some models









    Quote Originally Posted by specialguess View Post
    Ok I need some help with this one.

    Spark plug #5 on the spark plug wire and 2nd on from the fire wall

    I have 1 spark plug not firing...I disconnected the spark plug wire and the engine had no reaction. I turned the engine off and I found the spark plug wet with gas. The rest of the plugs are firing.

    I changed the spark plug wire with a spare one and I have no change didn't make a difference. I changed the the coil aswell no change.

    would it be just a faulty spark plug?

    will the TPS have any affect on the spark plug firing.

    I have fuel
    I have air
    just short 1 plug for firing

    1989 m20

    Thanks


    Later on that day...........................................

    Put a new plug in, I swaped out the rotor and cap and still have the same problem. that one plark plug not firing.

    -changed the spark plug
    -changed the spark plug wire
    -changed the rotor
    -changed the cap

    still plug number 5 (2nd from the fire wall) not firing

    Question? will the TPS or the AFM send signals to the computer not to fire that plug?

    I have a spare AFM and throttle body that I will try tomorrow.

    I did change the CPS 2 twice and no change in the engine

    I have all new hoses

    What about ICV will that send signals to the computer?

    Thanks


  4. #4
    Join Date
    Nov 2006
    Location
    Germany
    Posts
    475

    Default

    If the injector for cylinder #5 is spraying wide open or in a stream, the spark plug can't stay firing from the excess fuel.

    Swap the injector from 5 into another cylinder and see if the problem travels with the injector.

  5. #5
    Join Date
    Dec 2004
    Location
    Sydney, Australia
    Posts
    4,331

    Default

    Good thinking... if it were the injector driver in the ECU, you'd lose three at a time. The coil wouldn't single ot one, only the wire could do that. Is it the plug? An inobvious crack might cause a short- or it may simply not work or be faulty. New ones can do this

    A compression test as Bill already suggested might be the best place to start tho. How long has it been doing it?

    Join the Aussie
    540i LE yahoo forum

    08/88 535i e34 M30+miller MAF, 'stiens, tints & teeth!

  6. #6
    Join Date
    Feb 2006
    Location
    Oldham, England
    Posts
    3,077

    Default

    Is it possible your spare plug lead is also duff? Switch no. 5 with one of the other cylinders to confirm

  7. #7
    Join Date
    Oct 2005
    Location
    Markham, Ontario
    Posts
    57

    Default

    Thanks guys I am going to try your ideas as I am stumped.

    I will switch the spark plug with another cylinder
    try a different plug
    switch the injector to another cylinder
    try another spark plug wire

    Thanks Guys. I really appreciate the input
    1989 BMW 525 - M20--119,000.00-Original KM - now 5-speed


  8. #8
    Join Date
    Nov 2006
    Location
    Germany
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    Default

    Quote Originally Posted by Bill R. View Post
    Do a compression test on that cylinder.... no compression=no combustion=wet spark plug.
    The OP said "wet with gas." Your theory holds with compression leaks from both worn rings and bad valves, right?

    I figure bad rings would leave oily, blackness on the plug which should be very easy to see that it isn't 'gas.' Unless the OP's car had 'virginal' oil...

    Either way, a compression test followed up by a leakdown test for the weak cylinders tells much.

  9. #9
    Join Date
    Oct 2005
    Location
    Markham, Ontario
    Posts
    57

    Default

    so I have some time now to try and figure out my problem.....Happy New Year eveyone

    I tried another spark plug with a spare spark plug wire and I have spark from the Cap to the plug. Took out the new plug I put in and tested it and I have spark. All plugs are now sparking. I put back all the plugs and wires and I still have the same problem. cylinder 5 still not gettting aything from it.

    took the spark plug back out and it is dry with slight traces of gas on it. it's got to be that injector. I have taken the injector power bar off and I have found the connections to be a little pushed in. I fixed the connector and I am still going to switch the no 5 injector with another one and see if makes a difference.
    1989 BMW 525 - M20--119,000.00-Original KM - now 5-speed


  10. #10
    Join Date
    Jan 2004
    Posts
    4,148

    Default

    Not always, the plugs aren't always oily from bad rings. With no compression its very hard to get the gas to light so you end up with gas soaked plugs, doesn't have to be oil fouled.



    Quote Originally Posted by bsell View Post
    The OP said "wet with gas." Your theory holds with compression leaks from both worn rings and bad valves, right?

    I figure bad rings would leave oily, blackness on the plug which should be very easy to see that it isn't 'gas.' Unless the OP's car had 'virginal' oil...

    Either way, a compression test followed up by a leakdown test for the weak cylinders tells much.


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