Distributor Cap Question

I hope this is the proper location to post this.

Last week the F134 ran for the first time in many years for an extended period of time. It was rough, but sustained for many minutes. Yesterday, when I tried starting to begin a tune-up, barely a sputter, and when it did, it was a sputter with one cough then nothing. I'm still chasing down the reason, but in my investigations (was always told to check for spark and gas), I am fairly certain gas is arriving as the accelerator pump squirts a little gas down the throat. Static timed it and then discovered, using a timing light, that no spark is arriving at #1. Here's what I tested:

• tested each wire with the timing light...2, 3, and 4 all flash, #1 does not
• put #1 wire in #2 post on the cap and got flash in #1 wire, so I assume wire is fine
• tested resistance from inside cap to receiving end of post on outside of cap... continuity
• rotor looks clean, tabs inside cap look clean
• no apparent cracks on cap

So, being an amateur, hobby mechanic, none of this makes sense to me. Could the cap be at fault? (Like in only one of the four posts failing?) Could the wires (fairly new) be at fault if they all appear to work? Anything else come to mind? My gut tells me it is somehow the cap... despite it's good, clean condition.

I also have a grounding spark plug that clamps to frame so when you attach it to spark plug wire and crank, you should see an obvious spark. (It sort of confirms what the timing light shows.) Did not see one.

Thanks for any suggestions.

Eric

 

Try a new cap?

 

I will... was just trying to save a trip to the store. Might need to order one. But thanks.

 

A rotor and cap are good spares to have. Old caps often die by carbon tracking. You could have a path to ground from the #1 terminal. Moisture in the cap does the same thing.

 

In a different class of vehicle I have twice had aftermarket rotors that developed internal grounds, with absolute no external sign, and they tested perfectly.

Killed the ignition, but intermittently, and made me crazy trying to diagnosis the problem. Even sent one distributor to professional tuner and he missed it too. NOS rotors cured the issue.

This would NOT be your specific problem, but an example of what can happen with High Tension electrical parts.

 

I'm still chasing this down... another question comes up: Can a weak voltage from the coil still make an induction timing light flash but not be adequate to cause spark plug to spark? I pulled the plugs on 1 and 2 and connected them to the lead from distributor and used a jumper cable to ground the spark plug. On cranking, there was no spark. When plug installed, I could get flashes from #2, but still not #1. Then #2 dropped off. Could this be a failing coil? Primary resistance on an ohm meter is 2.4 ohms and in secondary, 10,770. Somewhere I read that this alone is not enough to confirm health of coil.

Thanks, all!

 

And if you did this already, if you filed or sanded them be sure to wipe the points clean with a piece of paper, or a business card.

 

Thank you all for the great suggestions. Howard: Thanks for the tip on colors. I bought it at a garage sale but was not 100% sure how to interpret. Great help! Golden James: I decided to redo all the internal distributor parts thanks to your encouragement. Thanks. Pete: I will replace all with new and keep the old ones and do as you suggest... file and clean them. Good reminder!

I discovered a pinhole leak in the coil so it will definitely be replaced. Currently looking at a SMP UC12. Thoughts? Also, is there anything I should know about the oil leaking (very slowly) from it?

Eric