combustion problems - HELP

Discussion in '1974 - 1978 Mustang II Talk & Tech' started by cobra_2_76, Jul 25, 2004.


  1. cobra_2_76

    cobra_2_76 Founding Member

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    :bang: I have a problem I just can't figure out. I'm getting fuel to and though the carb, floats ok, 66 primary jets, 68 in secondary. Idle screws about 1 turn out. I'm getting spark to the cap and plugs, verified MSD box works fine. No fuel filter obstructions.

    But it won't run. I can get it started once and awhile if I turn the dist to about 30 degrees advanced, but if I return it back towards 10 degrees it dies, and becomes harder to start. It also appears to be harder to start when warm.

    This engine ran really nice up to about two weeks ago when I noticed a slight miss or something when driving it at 60 mph, just barely noticeable. Mechanic who was checking my drive shaft balance didn't notice any problems. Over the next week it progressively got worse... until it wouldn't start unless I started advancing the distributor as noted above.

    Originally I thought I had a broken coil wire to the horseshoe connector, so I replaced it with a new one. Didn't solve the problem.

    Replaced the plugs, cap and rotor, just in case something was amiss there but again no difference.

    Any suggestions......one thought I had was whether the carb is passing too much fuel, maybe a cracked carb body? Crack worsend over couple weeks? Would that explain why it might run 30 degrees advanced? (advance gives the engine time to burn the fuel but at 10 degrees floods out?)

    :shrug: I'm open to any ideas

    Other particulars:
    9.0 compression
    351W heads
    Blueprinted Duraspark by Accel
    MSD 6AL box
    Mild cam
    about 8,000 miles on engine
    does not burn oil or consume fluids
    17 inches vaccum
    Edelbrock Performer manifold
    Holley 600 4150
    Holley mechanical fuel pump
    #1
  2. 2muchtime

    2muchtime Founding Member

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    distributor problems..i would not say carb
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  3. jeffnoel

    jeffnoel Founding Member

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    Are you still running the Duraspark box with the MSD?
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  4. cobra_2_76

    cobra_2_76 Founding Member

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    Yes, duraspark functions as a magnet trigger to the MSD box. Box works, new cap and rotor, new plugs.

    As I said it will run somewhat cleanly at 30 degrees at the distributor, but that ability also seems to be degrading. Will run less and less.

    One other thing I'm going to look into as soon as the battery recharges is the timing. I wonder if the cam pin may have pulled out and be in the gear and eccentric. Maybe slowy shifting around, but not completely loose? Would explain why I still have fuel pressure.

    Dave
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  5. Mstng2

    Mstng2 Founding Member

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    stock timing chain? setup? Pull the distributor and check the gear for movement.
    #5
  6. jeffnoel

    jeffnoel Founding Member

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    I just don't see the need for the Duraspark when running an MSD ignition. I bought the adapter cable that plugs the MSD directly to the Distributor and removed the Duraspark completely.
    #6
  7. cobra_2_76

    cobra_2_76 Founding Member

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    I didn't purchase an entire ignition system from MSD. When I mention duraspark I'm referring to the distributor not the igniton module. (This is a remanufactured/blueprinted unit done by Accel) The distributor is functioning as the trigger to power the coil and to distribute the spark to the plugs. The MSD box generates the signal to the coil and functions as a rev limiter.

    Dave
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  8. jeffnoel

    jeffnoel Founding Member

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    Gotcha, my bad.
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  9. dmoody

    dmoody Founding Member

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    How does it crank up if you pour gas down it? This would rule out the carb if it ran good albeit briefly. Advancing it 30 degrees on an engine that was running fine before says to me it must be the distributor. Engines with large cams can run fine on that sort of timing but you didn't change the cam. The plug wires are also still suspect. I've had plug wires go ditzo on me before from breakdown over the years. Anyway that is my best wisdom.

    d
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  10. cobra_2_76

    cobra_2_76 Founding Member

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    I started tearing down the front of the engine last night.

    One other site I posed the question to reminded me that the cam bolt washer does cover the pin dowel hole, therefor making it virtually impossible for the pin to come out the front. If it went out the back the fuel pump eccentric would be spinning and not giving any fuel pressure.

    Before I get to pulling the water pump on I'm going to pull the distributor one more time and take a close look at the distributor gear to see if that pin sheared. I'm hoping it was the one rather than a timing chain issue.

    Any other distributor parts that could alter the rotor alignment that I'm not thinking of???
    #10
  11. dmoody

    dmoody Founding Member

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    Before you go through the trouble of tearing down... I'd double check all the simple stuff again... you said you replaced the cap which means you could have gotten the wires mixed up... make sure everything is kosher there... also I suspect a plug wire could be causing all of this... I'd take a long plug wire (#4, #8) off another working engine and alternate switching it out on each plug, then running it to see if it makes any difference.

    d
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  12. cobra_2_76

    cobra_2_76 Founding Member

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    When it runs it runs very smoothly, with no miss fire. I did run through the wiring to make sure everything was as it should be.

    I found last night when rotating the engine to past the intake valve opening position that the rotor was at least one pole away from the number one position on the distributor cap. Sounded like the cam alignment pin, or pin for the distributor gear wasn't working as it should.

    I will also be double checking the gear pin on the distributor before progressing hoping it's what's wrong.

    Dave
    #12
  13. Wart

    Wart I'm Mad as HELL and I'M not Gonna Take it ANYMORE! Founding Member

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    But not to break or waller out the pin bosses. If I remember correctly your problem with the pin was finding one that fit snug in the hole?


    You really didn't answer the question, after cranking the distributer does it run (normally) above idle? The answer to this question would determin my next move.

    If it were a worn drive gear or sheared distributer pin it should run normally after turning the distributer, untill it wore or slipped a little more.

    Also you've been having long term ignition problems. Those may have been rooted in the harness common to your last and this system. But those are bypassed easily enough.
    #13
  14. Wart

    Wart I'm Mad as HELL and I'M not Gonna Take it ANYMORE! Founding Member

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    So much for starting a post then going to the shop and pulling a cam to see something.


    So it revs up just fine?
    #14
  15. cobra_2_76

    cobra_2_76 Founding Member

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    My problem with the pin was a long time ago!

    To get it running I had to move it to 30 degrees advanced as registered on the balancer. If I moved it back to 10-15 it would die. Rev up, yes it would at 30 degrees...notice I said it would. No longer running at even 30, which points to either something part degrading badly, or timing is moving.

    Thought...if the cam had moved enough to move the rotor one pole, I imagine some metal to metal contact might be evident. Haven't heard a sound from the engine, so again I'm hoping the pin sheared on the distributor drive.

    Past ignition problems were with igniton modules. Original one died, as did the Ford Motorsport Duraspark ignition module, made by MSD. Two in two years to me would seem to be a design issue. MSD 6AL box is zapping along fine, really an amanzing arch on the plug if you've never seen one.

    Most of the wiring was bypassed as the current requirements were higher and of a different routing than the Duraspark system.
    #15
  16. Wart

    Wart I'm Mad as HELL and I'M not Gonna Take it ANYMORE! Founding Member

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    Sometimes it takes time for things to show up.




    Good, it would run faster than idle. Very important to have a clear answer to that point, funny how something so simple can mean so much.

    That it would run 'normally' with the timing cranked tells me I would pull the distributor and check the cam and distributor gear(s) for wear and try to determine the state of the distributor gear pin.

    I figure you'll find the distributor gear is spinning on the shaft because if you're missing 15 degrees of cam gear there wouldn't be **** left of it.

    OTOH, I've been wrong before.






    Didn't the first box go two decades?

    Funny thing about the ignition boxes, each year was different till '78, then Ford seemed to settle on a spec. Later boxes don't necessaraly work on earlier systems. NOTE: I would have to review my references to be sure of the differences.

    Another funny thing is there are some real junk boxes out there, and I've seen some real junk with Ford written on it.
    #16
  17. cobra_2_76

    cobra_2_76 Founding Member

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    Didn't the first box go two decades?

    Yes I guess it did!!!


    Another funny thing is there are some real junk boxes out there, and I've seen some real junk with Ford written on it.[/QUOTE]


    I was sort of counting that with Ford Racing and MSD names both on the box it would be reliable....guess I was wrong!

    I'm crossing my fingers that the distributor gear is loose!!!!
    #17
  18. cobra_2_76

    cobra_2_76 Founding Member

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    I figure you'll find the distributor gear is spinning on the shaft because if you're missing 15 degrees of cam gear there wouldn't be **** left of it.

    OH yes, cam and drive gears are perfect, no wear or missing teeth. So I'm hoping I can turn the gear on the shaft. Has to be a much easier repair than pulling the timing chain cover.

    Dave
    #18
  19. jeffnoel

    jeffnoel Founding Member

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    Maybe I'm out in left field but could your balancer have spun?
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  20. Wart

    Wart I'm Mad as HELL and I'M not Gonna Take it ANYMORE! Founding Member

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    Well, maybe. I'm not familiar with aftermarket distriguters so I'm assuming they're simular to stock units and use a spring pin.

    Just because you may not be able to turn the gear doesn't mean it hasen't turned on the shaft.

    If it were a clean shear the engine wouldn't have ran at all, but aparently it wasn't clean as the gear kept turning the distriburor (takes a bit of force to turn an oil pump, though not as much as I had thought). Which means it has done a bit of gouging. The gouging may keep the gear from being pulled straight off which means the pins would have to be driven out. Except their ends aren't straight, or aligned.

    You may have to cut grooves (or drill a series of holes, or both) 180 degrees apart and split the gear with a chisel.

    Of course I'm looking at this as a worse case. I've always hated when someone tells me all I have to do is ... then I get into it and it's a frigging nightmare. I would rather go into something knowing it could turn into a PITA and have it turn out "all that has to be done".

    And, of course, I'm assuming it's a spun gear.

    And, if this is the problem you may want to have the new gear double pinned.


    Now if it's the cam all you have to do is replace it and the lifters ......
    :rlaugh:
    #20

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