Technical Chasing a no spark issue

Mid 60s 230/250.
been sitting for decades. Last inspection sticker was 99. Turns over fine. No fire at all to begin with. Installed a known good coil, points set and a known good condenser. No local stores had one so I removed one from my running 292.
Runs but only on 2-3 cyls.
No spark on those other cyls.
Changed those wires. Still no spark.
Cap looks good.

I’ve got another dizzy. It’s on a 250 than ran well when I removed the engine.

note: diagnosing with an old school volt meter. Bout to bring my DVM from work home.

what’s strange is it still didn’t spark with the good condenser until I manually opened and closed the points. I was checking power at the points opened and closed. Screwdriver arced between the points and dizzy shaft. Then it started firing.
Kinda suspecting the dizzy now.

 

The first thing is I would check the wiring. An intermittent connection can drive you nuts.
I had an intermittent connection on a coil wire (1965 300, those Ford pop on connectors).
Also check connections in the distributor…..
Could it be losing connection during rotation?

 

Yep. I’ll get the DVM on it
Run a lot of points. Never had one do this.
Unknown engines. Start from basics. Carb was full of dirt dobbers. Removed and rebuilt the carb. Vacuum out the intake. I’ll do a comp test and remove the valve cover. Check for stuck valves. Check mechanical timing.
Got fuel, air but an intermittent spark.

 

First thing I do is run a hot wire straight from battery to coil and check how it runs/fires.

This totally eliminates the ignition switch side of things. IF it fixes the problem then I know it's not in the main primary ignition system. IF it doesn't fix the problem then it's a pretty good clue that it's in the ignition system itself. I.E. distributor ground, coil, points etc. or even the ballast resistor.

I like narrowing my problem search window to as small as I can make it.

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Agree!
I use the ****ogy of underground water or sewer. You don't trace every single inch until climbing down the main locations doesn't find it. I like to jump into the middle. That splits the suspect area in half.
That's what @lostone is doing, byp***ing the feed half. If it is fixed, it's upstream, if it doesn't it's downstream. It's 12 volts without the resistor, but for a test, that will prove out. Just not a permanent solution.
Now, with a no spark on some cylinders, it's showing that that feed is at least working some of the time.
What is different for half the cylinders is the points opening or a flaky coil or condenser. Since both were 'known good' before, I'd really look at the dist shaft play. Use dwell to check here, preferably with a needle sweep. Also confirm with a timing light that the cylinders are always not firing or if it's different cylinders at different times. You can also connect to the coil wire and see if you can spot this same always fires X, never fires Y. Both should be in the tool box and only takes a few minutes.

Also, I have seen a long dormant dist. have poor grounding due to corrosion. Wouldn't hurt to loosen up the clamp and swing it back and forth a couple times, then cinch back up.

You have been a great help on paint stuff here, I hope this at least nudges your diagnosis in the right direction.

 

file the points, put in new spark plugs, have fun

 

Pulled the valve cover. No stuck valves. All rockers are oiling properly.
For ****s and giggles I dropped in the other dizzy with new points and condenser.
Fired right up. Runs smoother but still not right.
Mechanical timing is good.
Goona look for my compression gauge
Has a funny fluttery exhaust sound

 

I'm wondering if the miss fires are grounding, low voltage, or short problems.

That why I run the hot wire, this way I know it's full voltage, no shorts in the feed wire etc...

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Power from switch is good. Same if jumped from battery.
Starts to drop like it should when running
Plug wires arcing at the distributor cap when you pull one while running. Didn’t light me up like that usually does.
Still missing
Gotta find my comp gauge.
Vibrates badly idling.
Smooths out reved up slightly but still missing on 2 cyls. Or no change when ya pull the plug wire when running.

 

Probably not your problem, but check the intake manifold to head bolts and carb bolts They have a nasty habit of shaking loose. I was also going to suggest the distributor since they often wore out the bushings and didn't fire the points on all cylinders. Good luck.

 

No compression on 4 and 5
At least we got em all at least trying to fire

 

Try compression with a plug in the other cylinder. Try it both ways.
Zero can be 2 valves burned or a head gasket. If there is a bit of compression with a plug in the other bad cylinder, it's head gasket.
At that point, it's decision time. Pull it apart and bare minimum, full redo or swap with another. Your time and money. I ***ume with that new facility being fitted, you have an in with machine work.

 

I’ll pump some air in it. Figure out where it going
Got a decent 292 on the engine stand.
another 250 as well.
Just hoping to make it go and stop for now. Then modify as I cruise it.

 

Yes, a leakdown tester is even better. I guess I should have ***umed you had access.

That funny flutter is telling. I hang a shop towel like a matador behind the exhaust and ease it toward the end. If it pulls back toward the pipe, you've got mechanical issues.

 

A head gasket is cheap and EZ.
The story on the truck was the engine was rebuilt. Then sat until I guy I know got it. The tree fell across it right after he got it. He tried to crank it 4 years ago but kinda got frustrated after the tree deal.
Anywho, the engine is super clean under the valve cover.
Probably worth a head and intake gasket.
The carb had a mud dobbers nest. Those ******s could have messed up the compression on the 2 cyls.

 

Same distributor cap or cap that was on the distributor that you put in? The cap may have a fault that you can't see just by eyeballing it.

 

Boroscope?
Fresh and sitting usually doesn't burn valves. The rings have to be seriously stuck in the piston to pump zero. Sitting usually rusts the rings to the bores.
Wonder if someone didn't adjust the valves right?
Leakdown should give more clues. Easier to diagnose before tearing it down.

 

Ran the same with 2 different caps

 

Got one somewhere.
I’ll do a leak down and go from there

 

Since it's a rebuilt engine and I've also had it happen on a motor that sat for 10 yrs, squirt oil down the cylinders and try again.

Actually a couple cylinders lost oil on the walls and wouldn't build compression. Even after it was running with about 20 minutes of run time. I squirted some oil down all the cylinders, put the plugs back in and started it. Within a few minutes it started sounding better and better.

Pulled the plugs, stuck new ones in it and drove it daily for over 8 yrs with no problem.


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I had a bad new NGK plug a couple years ago. Whenever I have a miss now, I swap the plug from that cylinder with another cylinder to see if the miss moves. If it doesn't, it eliminates the spark plug.

 

With it running, wiggle around any of the wiring between the coil and the distributor and see if it acts up. Look especially closely where the wiring p***es thru the distributor housing. Check the grommet in the housing and make sure it's still insulating properly. If the grommet has a terminal stud on the inside, check for continuity by wiggling the lead between the terminal and the points with an ohmmeter connected. The constant movement of the vacuum advance plate flexes this wiring and can eventually brake down the connection.

 

I have seen lifters miss @ idle
bleeding off , above 1,200 no miss

 

Ain't old cars fun?

Have you checked the wires in the distributor? HRP

 

Check the muffler bearings!

 

It could be rust or carbon on the valve seats. I helped a friend get an old english ford six going by tapping the valves a few times with a hammer. This makes the spring close the valve sharply and can break down the rust or carbon. If you want to try it make sure you only hit the valves that are supposed to be closed.

 

Yep. I’ve used compressed air and tapped the valves with a hammer a few times and the air stopped.

 

Says "I hit cars with hammers". Nothing about tapping.

 

Hammers. The universal tool. from battle fields to surgical rooms.

 

You left out duct tape