The Stovebolt Site Forums The Shop Area Engine Shop Dead or part dead cylinder

My 261 has a miss. I can't hear it so much under the hood but the exhaust sounds "boom, boom, etc.

I put a timing light each wire. All flashed except one. Wire 6 was inactive. I switched wires and still, the wire on 6 wouldn't flash. I replaced the points. Still, #6 wire wouldn't flash but the other 5 did.

I pulled the distributor cap. Things looked OK. I started it again and got some haphazard flashing from wire #6.

I'll see if NAPA has a new cap and rotor tomorrow.

Do these limited observations suggest anything? Thanks!!

Plug, wire, cap, rotor are the only things it could be.

Unhless the #6 cam lobe lobe on the dizzy is wiped but I doubt that's the case.

Otto, you bring up another thought.
If the disc and spring under the grease cup is not in place, the shaft could be wobbling so the points may not be opening correctly.

I thought of that but I think the miss would be a lot more random rather than only on a single cylinder.

I had a shaft wobble on the Galaxie 500 and it was completely random and would do it at different rpm and sometimes run perfectly smooth for a while. Wally's appears to be a problem isolated to #6 at all rpm.

Carbon fouled spark plug- - - -the wire can't develop enough voltage to trigger the timing light.
Jerry

I'm going to reposition each wire on the distributor to the next position clockwise. Should still run since the order remains the same.

If the problem is indeed with that #6 position on the distributor, the problem will move to the #3 wire. I hope this makes since and is correct. I'll do it this afternoon.

Pull the plugs and inspect. If they look good, switch #6 plug with another. Next step compression or leak down test.

Rusted Nut, he says he's not getting any spark on #6 plug. Whether or not the cylinder has compression is irrelevant.

Before going to all of that trouble, pull out #6 plug and just replace it and see what happens.

I didn't see he switched plugs, just wires. If spark is good, then I'd check compression.

Plug 6 looks good. 0.035 gap but wet with gas.

I then moved each wire at the distributor one space clockwise but it wouldn't start. It just spun with no ignition! I thought if the rotational order was maintained, it would run.

I'm going to sleep on it.

Put the wires back and switch the suspect plug to a different cylinder. 6 to 5 and 5 to 6 and see if cylinder 5 goes dead. Maybe you have a plug that looks good but is defective.

John

What does a whole set of plugs cost? What did a compression test find? How about a cylinder balance test? What's the resistance of each plug wire? Sun Electric Company got it right 70 years ago- - - - -"We test- - - -not guess!"
Jerry

Regarding the old Sun machines.. my high school auto shop had one, and it was considered kind of anachronistic by 1988, coming as it was from the early '70s. However its CRT oscilloscope worked great and was super handy for learning about/diagnosing ignition system issues. You could set it for vertical and it would show each cylinder top to bottom, you could easily spot a bent distributor shaft or wobbly bushings. Put it on parade and notice which cylinder had higher or lower voltage, indicating rich or lean or shorted/open wire and etc.

I kinda wish I had one, although it was so big, I'd need a separate garage for it!!

All this drama over an open circuited spark plug wire or a shorted plug! They should have a maximum of 1,000 ohms per inch of resistance, and a cheap ohmmeter is all that's needed to check plug wire resistance!
Jerry