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Having a weird missfire/dead cylinder problem

Discussion in 'The Hokey Ass Message Board' started by slick 65, Feb 14, 2011.

  1. slick 65
    Joined: Feb 1, 2011
    Posts: 35

    slick 65
    Member

    well first off to day i took the hei out of my 65 ford that has a 302, i took it out because it had no spark with cylinders #2 #3 #7 constantly, fixed it once with new wires but then let the truck set for a week and right back to the same dead cylinders plugs looked fine put them in our zapper and lit fine, so i changed the plugs wires again and still did it even did a compression test for the heck of it, 120lbs all 3, well so i grabbed a good know points distributor through it in there same 3 cylinders dead! weird? cams not flat took the covers off rolled her over all was fine theres just no spark at the distributor with the 3 cylinders, so put a new coil in it then same 3 again, we did take a wire off the plug on the engine to put it on a loose plug while the engine was running and nothing just a very intermediate like 20seconds went by before another spark that was very weak same with the other 2 from the cap.

    please any input will help
     
  2. ok... since we get the facts straight is it a ford 302 with a HEI distributor conversion,
    or is it a chevy 302 with an hei dist? I confused...
     
  3. slick 65
    Joined: Feb 1, 2011
    Posts: 35

    slick 65
    Member

    sorry about that it was a ford with a hei conversion
     
  4. have you tried new plugs?
     

  5. slick 65
    Joined: Feb 1, 2011
    Posts: 35

    slick 65
    Member

    it has brand new plugs also, but i don't think thats the problem, its has a weak to no spark at all at the dist for cyl #2#3#7 while holding each wire just above the dist cap
     
  6. is it possible that the end of the distributor isn't fitting tight to the input on the oil pump? check the timing with a light to see if its steady. something in my brain is telling me a worn out distributor, but since its doing it with both distributors, it could be the bottom end of the distributor shaft. which could cause some shaft movement causing erratic timing and a miss on some cylinders. this is just a hunch though.
     
  7. DocWatson
    Joined: Mar 24, 2006
    Posts: 10,273

    DocWatson
    ALLIANCE MEMBER

    Its sounds like distributor drive, being consistent on cylinders and the same with two different dist.

    Doc.
     
  8. George/Maine
    Joined: Jan 6, 2011
    Posts: 949

    George/Maine
    Member

    My Guess it could be timing chain.If you take the dist out a put those dead cylinders with plugs out of engine and turn see if you have spark.Turn it my hand.
     
  9. The cylinders that are not firing are not next to each other or really connected in any way.
    1st question - did this motor run in this configuration at any time?
    2nd question - have you changed, to a new one not just a different one, cap and rotor?
    3rd question - Have you changed the condenser???
    4th question - Have you bypassed the Ballast resistor??
     
    Last edited: Feb 14, 2011
  10. jdj9410
    Joined: Sep 4, 2007
    Posts: 324

    jdj9410
    Member
    from Paris TX

    I'm with fuzzy night, The small block Ford intake is setup to feed 1,4,6,7 from the right side and 5,8,2,3 from the left if you are using a dual plenum. So 2 and 3 are not connected to 7 via intake. Sorta rules out a typical vacuum problem which is common on multiple dead cylinders. And on the distributor firing order of 15426378 if 6 was missing also, then the cylinders all missing would be in order yet it skips missing 6. And two cylinders are on one bank and one on the other bank. Is there anything common you have used between the 2 ignition systems. Wires, rotor(probably not, being that one is HEI), plugs etc.? Just going to have to start over and systematically check all the components. Definately a strange problem that is probably hiding in plain site.

    Edit: Maybe check voltage going to ignition system if it is full 12 volts. Low input may be manifesting the fault at these particular cylinders because they are weakest inheritably in the system or for some other unknown reason.
     
    Last edited: Feb 14, 2011
  11. THE FRENCHTOWN FLYER
    Joined: Jun 6, 2007
    Posts: 5,366

    THE FRENCHTOWN FLYER
    Member
    from FRENCHTOWN

    A couple of more things to try:

    stick a (unlit) propane torch down the carb to see if richening it makes it run better - this will eliminate any vacuum leak, like from the bottom of the runner seal

    check your rotor-to-cap-terminal gaps; maybe it is too large
     
  12. slick 65
    Joined: Feb 1, 2011
    Posts: 35

    slick 65
    Member

    i also though it may be the timing chain, since the engine seems a little loose in the lower end it may still have the original chain on it.

    will be giving this a try
     
  13. slick 65
    Joined: Feb 1, 2011
    Posts: 35

    slick 65
    Member

    could be? checked the resistance in the cap with a meter all read the same appears to be no abnormal wear in the cap or rotor, i may just pick up a new cap and see what happens.
     
  14. slick 65
    Joined: Feb 1, 2011
    Posts: 35

    slick 65
    Member

    1st question - did this motor run in this configuration at any time: it ran with the hei for a very short amount of time than the truck sat for a week then back to the same problem

    2nd question - have you changed, to a new one not just a different one, cap and rotor: its not a new rotor or cap im going to go and get one and see what happens.

    3rd question - Have you changed the condenser: Have not

    4th question - Have you bypassed the Ballast resistor: Have not will give this a try
     
  15. slick 65
    Joined: Feb 1, 2011
    Posts: 35

    slick 65
    Member


    everything was changed when i swapped the distributors over, yeah im thinking its going to be somthing simple, ive never had this problem before.

    (Maybe check voltage going to ignition system if it is full 12 volts. Low input may be manifesting the fault at these particular cylinders because they are weakest inheritably in the system or for some other unknown reason) : never thought of that will give it a shot.
     
  16. slick 65
    Joined: Feb 1, 2011
    Posts: 35

    slick 65
    Member

    will do thanks!
     
  17. George/Maine
    Joined: Jan 6, 2011
    Posts: 949

    George/Maine
    Member

    If you have another dist with wires
    Put some spark plugs on end of wires,grd them and grd dist,then take 12 volts direct to dist,now turn by hand and should see each plug fire nice napping sound.Your very own dist machine LOL
     

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