65 merc 350 2 cyl spark only on one plug

[Rut13]

my 65merc 350 only sparks on one plug when i turn it over. changed coil,plugs,condenser, and reset points no luck. any suggestions will help me from pulling the rest of my limited hair out.

 

[WildWillJAX]

Re: 65 merc 350 2 cyl spark only on one plug

Have you checked the spark plug lead? A simple check would be to switch the spark plug leads from one cylinder position at the plugs and coils/or distributor. If the problem moves to the other cylinder then you have a faulty plug wire. IF so, change both they are usually sold in sets and tend to wear out at the same rate.<br />The long answer would be to do a resistance check on the plug lead using an ohm meter. Compare the resistance value of the wire with the specs in your manual to make a determination as GOOD or BAD. In addition, the outer covering of the wire (the insulator) could also be bad allowing the secondary voltage to short to ground before reaching the spark plug. Check the condition of the insulator for cracks, bare spots and areas that appeared to be burned or melted from heat. If anything abnormal is seen, replace your plug wires.<br />Generally speaking, the points and condensor are never a likely suspect for a single cylinder problem in that the points and condensor make up part of the primary circuit and are common to all cylinders. If they fail, all cylinders would experience the same problem. Your problem most likely lies in the secondary circuit (high voltage)which originates at the coil, passes through a distributor cap (on some engines) through the plug wire and then to the spark plug.

 

[Laddies]

Re: 65 merc 350 2 cyl spark only on one plug

the 350 has a set of pts-condenser and coil for each cyl. acting like two seperate ign. systems one for each cyl. the most common problems are pts. and cond. although once in a while a coil will fail---bob

 

[Rut13]

Re: 65 merc 350 2 cyl spark only on one plug

i checked the plug wires they checked out ok.will change points and see what happens. thanks for the advice. this sight is so helpful and the great people here make it so.

 

[emckelvy]

Re: 65 merc 350 2 cyl spark only on one plug

If you did not change or clean the points then then are very likely your problem.<br /><br />The only effective way to clean a set of points is to remove them. If you try to just run sandpaper down the gaps, you likely will not get them clean enough.<br /><br />I'd recommend that you pull both sets of points out, and clean them with 280/320 grit wet/dry sandpaper (wrap the paper around something thing like a ruler, etc to get a flat surface to bear against); or on a whetstone, then polish with crocus cloth.<br /><br />Degrease with lacquer thinner or other suitable solvent and reinstall. Gap to .020". Smear a very thin coating of lubriplate or other thick grease on the points cam.<br /><br />If you still are having spark problems in one cyl, you can swap the major components back and forth until you isolate the problem.<br /><br />Also check any kill switch wires connected to the points as you may have something grounded out.<br /><br />HTH and let us know what you find.........ed