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cylinder not firing

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notshy Learner Dubber

5 posts · joined Feb 2011 ·

#827911
G'day Guys!

New to the formum...but hoping you can help me out? I have a 1500 bug that has started to run rough. We haven't had it very long so we went through and put new plugs, leads, points and condenser on and still no joy. The mech at work said it sounded as if it was electrical. It does start but pulling the back left lead off does not affect it when running, pointing to that port being the prob. Plenty of spark, compression about 100. It did come good for a couple of days at the beginning of all the dramas after I played with the leads but it only lasted a couple of days before it did it again. I'm starting to run out of ideas, any of yours would be greatly appreciated!!

65standard Officially Full-On Dubber

373 posts · joined Apr 2009 ·

#827933
The back left lead is No.4 cylinder. Forward left is No. 3, Rear right is No.2 and forward right is No.1

When you pulled the plug off, what did it look like? Was it oily? If so, you could have shot rings in that cylinder.

Have you checked your valve clearances? They could be too large, opening too late and closing too early. it's possible to have them out in one cylinder, making it run rough. The clearances should be .006" to .008" depending on who you talk to.

Hope this helps.
If it ain't broke, fix it till it is!

Big Al Learner Dubber

6 posts · joined Aug 2009 ·

#827989
I had a similar problem with my VW after fixing an engine fire in that I put the leads on incorrectly. For some reason my engine has been tuned to fire off no.3 rather than no1 so the leads on the distributer are different from the book? I managed to start the car but it ran very rough.

Also check that your dizzy hasn't moved ( timing).

Joel Now containing 100\% E-Wang

9,368 posts · joined Feb 2006 ·

#827990
That compression is a tad on the low side, not badly but certainly not factory fresh engine.

waveman1500 Also rides a Honda

1,346 posts · joined Dec 2009 ·

#828075
Joel wrote:That compression is a tad on the low side, not badly but certainly not factory fresh engine.
This is true, but 100psi is still enough to have it run nicely and fire on all four. Have you looked at the distributor cap, rotor button and maybe even the points cam inside the distributor? Sometimes the points cams can round off with neglect if they're never oiled.

Also look for other faults, is the exhaust blocked? Intake manifold? Do the valves go up and down properly when you turn the engine over by hand?

Oh, and the cylinder numbering that 65standard gives is only correct if you refer to the rearward end of the car as the 'back' cylinder and the cylinder closest to the driver as the 'front'. Because you work on the engine from the back of the car and reach into the engine bay, I tend to call #3 and #1 (up against the firewall) the 'back' cylinders, and the ones closest to the engine lid the 'front' (#4 and #2).
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ratty 63 Custom Title Time!

1,083 posts · joined Oct 2003 ·

#828164
Might be a long shot - but have you flooded the engine recently?

I have found that once the spark plugs have been soaked in fuel they don't recover any more. Not sure why - never used to be a problem... perhaps it's the new fuel or a change in the materials they use in the plugs....

It's also not impossible to have an internal short in a spark plug, even when they are brand new.

Before you get too involved in removing parts for testing it might be worth changing the plugs (particularly the plug in the cylinder that isn't firing) to check....


R 🙂
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notshy Learner Dubber

5 posts · joined Feb 2011 ·

#828176
Thanks for the tips guys, it's given me a few things to look at. My mate has a few parts eg dissy, rotor button that I might try and fault find with. I did swap all the plugs around to see if it was the 1 dodgey plug, but not the case. The plugs just appear all the same ...just a bit black.

notshy Learner Dubber

5 posts · joined Feb 2011 ·

#838391
Well I've been away for a while and not really much the wiser but the bug did come good after a new plug and a good hard drive out on the open road to clean it out! Thanks again!