Itinerant Air-Cooled

Ok. The engine in my thing started idling rough. I tried pulling the distributor wire for #3 and no change. Then I tried #4 and still no change. Then I pulled both of them off and it still didn't change the idle. I was surprised that it would keep running with only the #1 and #2 wires on. I checked the compression at 95 on #3 and 120 on #4. The plugs were sooty black.
Before this all happened I forgot and left the key in the run position all night and the battery was almost drained. After charging it up is when I found the 3 and 4 plugs not firing. What damage might I have done?

mentalQtip wrote:Before this all happened I forgot and left the key in the run position all night and the battery was almost drained. After charging it up is when I found the 3 and 4 plugs not firing. What damage might I have done?

As far as having it sit on the Run position, nothing. It just supplies power to an uncharged system.

Ok, thats great. But why did the engine start idling rough and the 3 and 4 plugs stop firing?
Or what is the likely reason that 1 and 2 plugs fire normally and 3 and 4 don't?

Thanks

Gas, Fire, Air.

Since it's fire you're missing, time to look at your wires, plugs and everything along the way. The power-on can be a false lead or not, so just start working your way up the river (i.e. wires) till you find where the current stops.

Best,

Lanval

Lanval wrote:The power-on can be a false lead or not, so just start working your way up the river (i.e. wires) till you find where the current stops.

Ditto, my brain is too fried to put that into words.

I have heard that leaving the ignition on can harm your points but that would affect all cylinders, not just two... do as the others have suggested and start tracking this down methodically.

As the others have said, you gots no sparky to half of your reactor!

Pull the distributor cap off and see what condition your condition is in. In theory, you could have fried the points by leaving the key on, but that would affect all four sparkys, not just two. No matter, check the points, rotor, cap and wires. Replace them with known good ones if anything looks hinky. BTW, you can't tell the condition of the wires by looking so you might have to shotgun those.

Yep points. Probably melted together.

Progress report:

I replaced the cap, rotor, and wires with new ones from Halsey. Not one bit of change. I can pull both the 3 and 4 wires with no difference in how it runs. I used a stethoscope to listen for air leaking at the intake manifold at both places where there is a seal and heard nothing. If the points were damaged wouldn't they not work for #1 and #2 also?
There is compression, fuel, and there should be spark with new cap, rotor, and wires. The plugs are new also.
What could affect only the left side? I can only think of a air leak, and the seals are all new also. Also it was running fine before so I wouldn't think that an air leak could be at fault.
For only running on #1 and #2 it runs pretty good.

Start the engine. Hold one of the plug side wire ends to something metal (without starting a fire!) and see if you have spark.
If you have compression then the only thing missing is spark. If so then it is ignition related. Distributor points or condenser.

I have to throw this out there, just in case, speaking from experience, firing order correct?


neal

Neil, I've had the firing order wrong more often than right. Couldn't get it to start for the longest time and kept checking the wires and finally figured out that they really were wrong.
I'm heading to Baxter's for starting fluid to spray around the seals of the intake manifold.
New parts:
points
condenser
cap
rotor
wires
plugs

I'm about to give up for awhile.

Joseph

Ok, then. The starter fluid made no difference in rpm, suggesting no air leak there.
The biggest clue I can think of is its only on the left bank, and it affects both #3 and #4. I wouldn't think that anything in the ignition system would do that. What if the head was loose? But 90 and 120 should be enough to fire. My biggest question would be what changed suddenly. I started it and it idled fine and later I started it and it doesn't.

Joseph

Have you confirmed the valves are opening and closing? Crank the engine as if you were adjusting the valves and visually confirm. That's all I can think of.


neal

You sure the distributor is OK?
Check compression again, but that's too high for loose heads.