Distributor Problem?

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Distributor Problem?



Distributor Problem?

Postby Fabius » September 21st, 2018, 8:34 pm

Hello All,

Several years ago my 1974 M151 A2 started running rough, like it was running on 3 cylinders. It would start up fine but as soon as it warmed up it ran rough. Changed the coil, plug wiring, distributor cap etc. still ran rough. Found a good distributor and when it was installed the mutt ran perfect. Fast forward to now. It is doing the exact same thing. I read that the problem the military had with these distributors was there was a copper rod on them that would crack and when the temperature changed the rod would go open or be a high resistance short? My question is: I see that the distributor electronic control module is available on eBay. Is the rod located in there.? If is not and I check the other usual subspects it looks like I may need to change out the distributor?

Thanks for your help.

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Re: Distributor Problem?

Postby m3a1 » September 21st, 2018, 10:35 pm

I think what your'e describing is the contact on the center of the cap. That contact serves all four cylinders so that's not gonna be exactly it, though this does not necessarily rule out a defective distributor cap altogether.

My suggestion is...do the easy checks first and treat this as an entirely new problem with nothing whatever to do with what may have come before.

Typically, we all generally agree that a wholesale change of parts (as you did by R&R-ing the entire distributor) may correct the problem (or not) but then, even with success, how will you know what you actually fixed? A distributor contains many things that may or may not be part of your problem.

Since you are insisting that one cylinder is mis-firing, see if you can identify exactly which cylinder is actually acting up. I would like to hear more about how you came to this conclusion.

If there is a problem that is identifiably related to one cylinder over the others, you're more than halfway there. My suggestion is - have a look at the plugs first and a visual inspection of the cap (here, you're looking for a carbon trace). Either should provide you with a visual clue as to which cylinder isn't doing well. If you see no identifiable difference between plugs and the cap looks right, perhaps the issue is not one of ignition but rather one of fuel delivery, loss of compression (such as a valve or valves out of adjustment) or other....all of which can produce a rough-running engine, even to the point that you would think a particular cylinder is mis-firing.

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