Cylinder #3 not firing

I am trying to get the CJ road worthy, started it up today and cylinder #3 is not firing. This has been an issue for a long time and I have just lived with it. The odd thing is sometimes it will kick in. I can remove the spark plug boot and it doesn't stumble, so I know that it's the culprit. Any suggestions?

 

A new set of spark plug wires will probably fix it.

 

I have tried a different wire and that doesn't seem to matter, maybe I am just buying cheap wires.

 

It may be the spark plug is bad. May be that the ceramic part of the plug is cracked.

 

I have changed it out in the past, same plug and it still happens. I will pull it tomorrow and take a look and clean it and see what happens. It's just weird it's always the same cylinder. Maybe a bad head gasket causing the plug to foul?

 

By the way, thanks for your help. I will let you know what I find out tomorrow.

 

Try a compression test?

Head gasket is one possibility. Take a look at the plug/cylinder first thing in the morning - residual radiator pressure can push coolant into the cylinder overnight.

 

Have you tried changing the distributor cap?
If so, take the valve cover off and have a close look at the valve springs for #3.
I once chased a miss fire around for a few days before I finally found a broken valve spring.

 

Had same problem, checked compression-five pounds less than other three- 105 should be 120, so my motors a little
put in a hotter plug and got it out on the road to clean out the cylinder, seamed to help but still coughs once in awhile

 

Would ALSO try the "stick a screwdriver in the plug boot and see if it sparks to ground" trick before going too much further. If it sparks to ground THAT way.... suspect plug..... if NOT.... then suspect wire, distributor, points, etc.

Another GOOD test...... start the bad boy up when it is DARK outside and, with no lights on anywhere, see if you can see residual sparks coming out of any of the ignition components......been there..... done that....

 

The compression test wil tell you alot. I would guess that #3 will be low. If so before you pull anything apart, adjust the valves. both intake & exhaust. They do get tight after awhile. Run it and test again. Good luck, and keep us informed. Thanks, Matt W.