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  1. #1

    Default " I have a 3.0L merc that star

    " I have a 3.0L merc that starts missing after half an hour, I took the carb off to have a look, and noticed a small hole in the plunger. Can someone tell me how the plunger works, and if the small hole could cause the above mentioned fault. (the engine seems to run ok at lower revs) "

  2. #2
    Join Date
    Nov 2005
    Location
    Oregon coast, Oregon, USA
    Posts
    141

    Default " Sounds like you have an igni

    " Sounds like you have an ignition problem. High speed missing, especially after heat builds leans toward a coil problem.If you have a points system it could be a bad condenser. If you replaced the condenser recently that could be it as condensers are sometimes bad right out of the box.In a system with distributor module, the module is the weak spot and is likely the problem.
    Eddie "

  3. #3

    Default " I've changed the points,

    " I've changed the points, condenser, plugs, rotar arm, distributer cap, coil, leads and checked the timing. The only thing I can see is this small tear in the plunger. "

  4. #4
    Join Date
    Nov 2005
    Location
    Oregon coast, Oregon, USA
    Posts
    141

    Default " Delster, Try another c

    " Delster,
    Try another condenser.As for the plunger it is an accelerator pump. You can get one in a carburator rebuild kit along with new gaskets.If you are into the carburator go ahead and replace it, but I seriously doubt it has anything to do with the symtoms you describe.
    ddie "

  5. #5

    Default " Tried another condensor, but

    " Tried another condensor, but it was still the same. Any more sugestions would be greatly received. thanks

    Delster "

  6. #6
    Join Date
    Nov 2005
    Location
    Oregon coast, Oregon, USA
    Posts
    141

    Default " Delster, Being that this

    " Delster,
    Being that this situation occurrs after a time it may be clogged fuel vent. If its not vented properly the engine will begin starving for fuel.
    Eddie "

  7. #7

    Default " thought of that too, I ran i

    " thought of that too, I ran it from an external tank, and it still did the same. I actually think its loosing power and not missing, and the carb was definetly making some strange noises when it happened.

    thanks for the help eddie, it's appreciated.

    Del "

  8. #8
    Join Date
    Nov 2005
    Location
    Oregon coast, Oregon, USA
    Posts
    141

    Default " Do you have an electric fuel

    " Do you have an electric fuel pump? Does this problem happen every time or intermitantly? Does the sound happen then? What is the sound like (buzzing , tickking , humming, ect.)
    Eddie "

  9. #9

    Default " The fuel pump isn't elec

    " The fuel pump isn't electric ( i stripped this as well) The problem happens after approx half an hour of use, and then only at high revs. If i drop the revs, it seems to be ok, although it runs bad. And the best way to describe the noise is a kind of vibrating noise. (sorry thats not too descriptive)

    Derek "

  10. #10
    Join Date
    Nov 2005
    Location
    Oregon coast, Oregon, USA
    Posts
    141

    Default " Derek, Good clue onthe

    " Derek,
    Good clue onthe noise. Could it be comming from the valve cover?
    I'm suspicious of a hot spot causing a valve or piston to sieze. I'd suggest replacing the thermostat. Get the right one. It should be about 143 degrees for a raw water system, 185-195
    for an enclosed coolant system. Next I'd consider the water pump impeller.
    I trust your oil is up and is kept clean.
    How old is your engine?

    Eddie "

  11. #11

    Default " I've replaced the thermo

    " I've replaced the thermostat already, but haven't even thought about the impeller. I'll give that a try this weekend.

    The engine is a 1989 model.

    thanks again Eddie

    Derek "

  12. #12
    Join Date
    Nov 2005
    Location
    Oregon coast, Oregon, USA
    Posts
    141

    Default " Derek, One other thing

    " Derek,
    One other thing you might check out is the ignition switch. As ignition switches get old on boats or cars they wear out. As the engine runs the vibration gradually moves the worn contacts aqway from each other. At this point I'd check it out.An easy fix if thats what it is.
    Eddie "

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