Still no fire on #1 plug

[JBohannon]

I was not getting fire to my #1 plug. So I bought rotor body, new rotor, and rotor cap. Put them all on and all cylinders fire ok for about 5 miles. Then the only thing I did was lower idle speed a little and soon #1 quit firing. When I say no fire I could not get fire to jump or even a timing light which lights on others will not light. I switched plugs that did not help. Now I realize I do have fire to #1 if increase engine speed. Any ideas.

[J Franklin]

Ask for a new distributor body.

[Kahuna]

You may have a worn distributor cam causing this problem

[newshirt]

Here's one possibility: If you had excessive play in the distributor shaft or upper distributor plate, it could cause the points to remain closed while the cam is in plug # 1 position. Consider checking the point gap on all four cam lobes, and wiggling the distributor shaft to see if there is excessive play.

[steve s]

This is a really interesting case. Wracking my brain to think of things that get better at higher engine speed, especially for just one cylinder. Not much.

First, can you confirm that you changed the distributor body? Is that what you meant by "rotor body"? Like J Franklin, that would be my first choice.

In case it's the distributor cam (somehow), could you rotate the cam so a different lobe is activating #1 spark plug? Then see if #1 still craps out on you.

My personal far-out theory is that there's an intermittant short somewhere grounding the spark (could be either primary or secondary ignition circuitry) but only at low speed. My creative theory is that the jiggling and vibrations at higher speed result in the short's contact being broken. The converse would work too, i.e., only at high speeds is there a vibration-mediated good contact in the #1 circuit--again--whether primary or secondary I don't know. A bit far fetched, I know, but I'm waiting to here a better idea for the speed effect. You're not running a magneto, right?

Steve

[JBohannon]

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No not running a magneto. I will definitely check the lobe and points gap at all 4 lobes. I think what happened is I put on the new distributor body, rotor, and cap and it ran fine. Then when I decided to lower the idle speed it quit firing and fouled the plug. It does fire when I raise the engine rpm. Just cannont figure that one out. Maybe it is a short somewhere. I could be wrong but it does seem the spark is better at higher rpm on all cylinders.

[JBohannon]

One other thing I should mention. My ammeter is missing and I have ordered a new one. the previous owner have the 2 wires going to where the ammeter was just wired together. Should this have any effect.

[pat in Santa Cruz]

I would check shaft bearing wear and wobble, as well as the cam. The Argentinian repro cams were very common back in the 70's, and are notorious for uneven grinds. A loose distributor shaft might not deflect so much at high speed. The combination of a poor cam and too much wobble can create some odd timing issues. You changed everything else..focus on whats still the same.

[newshirt]

Maybe the coil polarity is backwards and you just have weak ignition voltage. In this case, maybe the #1 plug is just the unlucky one that can't fire, and the rest are close behind. See the link below for a polarity tester. Or try a "C Spark" device to test voltage.

http://www.brattons.com/product.asp?...=any&PT_ID=all

[Tom Wesenberg]

As far as a timing light, you might have to insulate the metal spark plug straps. My engine scope inductive pickup won't work unless I put some plastic tubing around the metal strap.

[JBohannon]

My timing light works fine on all 3 other cylinders. I hope to check lobes today. One thing is for sure sometimes I get fire to #1 and sometimes I do not. And I could be wrong but it sure seems related to engine speed. Thanks, Joe B.

[V4F]

#1 does need the clear tubing on it as per nu-rex . maybe not your problem , but it is a requirement ............... steve

[steve s]

Originally Posted by JBohannon

One other thing I should mention. My ammeter is missing and I have ordered a new one. the previous owner have the 2 wires going to where the ammeter was just wired together. Should this have any effect.

That can't have any effect on your problem; it's just one less possible bad connection to worry about. Otherwise, the only thing is that without an ammeter you're missing out on a nice diagnostic aid for other possible electrical issues.

Steve

[JBohannon]

Steve Norcal Thanks for the info. What is it a need for #1 as far as clear tubing and why ? Thanks, Joe Bohannon

[CarlG]

My timing light is NOT the inductive type, but rather requires direct contact -- so the metal spark plug straps work just fine. If I use covered wires, I have to introduct a bare wire in the circuit anyway.