3 cylinder Model A

Check the distributor cam to be sure it's opening the points properly/adequately for each cylinder.
 
You got it! Rookie error, I should have changed the HT wire long ago. Feel free to get on a plane and come kick my backside, how stupid am I?

But I will say all the other stuff like degreasing the housing and new wires has greatly improved the running. Thank you to all.
 
For some unknown reason the path to the #1 cylinder was a little weaker than the rest. The defective high tension lead was diminishing the voltage to the point were #1 was not firing.

I carry a spare high tension lead with me when I tour.
 
Well folks it’s back again, never sure it went away for long. Do I change the ht lead again, it’s brand new? Everything is brand new, even new style points with the condenser in the distributor. Short each plug lead to a head nut, you see a spark, engine stutters. Short #1, no spark, but pull lead off and 1” spark to head nut. New wiring to the dash, I’ve even bypassed the ignition switch try to eliminate possible shorts.
 
Jembow,take #1 plug out ,connect strap to it and lay it on head. Try engine again and watch for spark on #1, no spark either the plug is bad,or the lower distributor housing has a ground short. My bet is the housing.
Don S
 
OP - There is a fat 1” spark to each plug.


eagle said:
....... Also possible, of course, a bad plug.
Click to expand...


Bingo. No sense in over complicating this. If the spark is at the top of the plug and the cylinder doesn't fire it has to be the plug.
 
It only needs Compression, fuel, & spark at the right time. you only need to find which it is missing. Did you ever remove the plug and add a squirt of gas in that cylinder and see if it would fire? What is your plug gap?
 
Make sure the high tension lead is shoved all the way in on both sides.

Something is reducing the voltage to the #1 spark plug. The plug will fire when sitting in air but when the pressure is higher in the combustion chamber it takes more voltage to fire it. I cannot remember all the things you did to try and fix the problem but you might try a different brand of spark plugs. Did you use your multimeter on the ohm setting to check all the paths to the plug?
 
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How did the recommended test for the intake runner to number 1 go. If you spray it with starting fluid or similar and the engine speeds up there is a leak.


John
 
#1 plug hole rusty krusty and a bad ground ? If shorting to ground with a screwdriver from #1 spark plug and you don’t see a spark the electrons have a better path to ground through a carbon trail ! I don’t think you can remove a carbon trail from inside a distributor cap/body permanently ? If the normal path of electricity gets broken like removing a plug wire that potential will go to ground forming a carbon trail ,you may never see an ark/spark . A prank at work was to use a lead pencil inside of a distributor cap causing an engine misfire and grief for a mechanic
 
Thanks, I will try all suggestions, I agree it must be tracking off somewhere, but I've tried several different caps,wires plugs etc. Probably won't get back to it till Sunday. I'll report back
 
Just fitted a new exhaust manifold, new gaskets. All sealed up nice and snug.
Besides it's a Siamese port, a leak should affect 1 & 2.
 
I know you said you did a compression check but maybe your valves are not consistently sealing or seating. Rerun a series of compression messurements on #1 just to see if there is a large variation in the data. I have had experience with a new set of valves not completely sealing due to small step in the stem diameter. Your stems could possibly have a small amount of carbon buildup which could prevent consistent sealing.
 
As you said, it could be a sticky valve. The original poster said: "I only put in new rings and did a valve job." He reported that the compression was good, 70 psi. Might be interesting to do a compression check on that one cylinder while the engine was running on the other 3. I don't know if anyone has ever done that.
 
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