Front Two Cylinders stopped firing

DScott

DScott

Junior Member
I have a 29' Model A. It has been running great, and then it started running rough. Turns out the first two cylinders from front to back stopped firing. I checked distributer, and I am getting fire to the plugs, but they are not firing. Bought new plugs, set the gap, still not firing. Somebody told me the exhaust valves are notorious for sticking. Any ideas on how I can unstick these valves ? I tried spraying Marvel Mystery Oil down the carb while it was running, and that so far has not worked. Any help will be appreciated.
 
Not likely valves would stick on two cylinders at once. Do a compression test. May be a head gasket leak between those two cylinders. Also check intake gasket, although less likely.
 
Run a compression check. When two cylinders next to each other go at the same time, my first thought is a blown head gasket between the cylinders.
 
Whenever two adjacent cylinders suddenly "go dead", you can bet it's a blown head gasket between them, as previous posters suggest. I am just adding my agreement. The metal in the engine block between cylinders #1 & #2 and #3 & #4 is very narrow and if the cylinder head nuts are not torqued properly - and periodically checked - it's easy to blow out the gasket in these areas. Or it just might be the head gasket's time to croak after many years, especially if the engine had gotten really hot in the past and slightly warped the cylinder head.
All you need to do to check for a blown head gasket is to remove both spark plugs in the affected cylinders and with your thumb covering a spark plug hole, push the starter rod, ignition key OFF. The engine should turn over faster than usual if the head gasket has blown out between the cylinders. If no puff of air wants to push your thumb off the spark plug hole, given the suddenness of both cylinders dying, the problem is almost certainly a blown head gasket. If, however, the compression does push your thumb off one spark plug hole, but not the other, it could be blown gasket in that cylinder, a broken valve spring or a stuck valve. But since both cylinders went dead at the same time, my money's with the previous posters: a blown head gasket between cylinders #1 & #2. When you remove the head to replace it, you'll be surprised at how narrow the metal edge is between the cylinders.
Marshall
 
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When the head is off, look for little, lightly etched round spots, near the top of the cylinder walls! That's a SURE sign of a gasket leak, between the 2 cylinders! They're from water leaking down, AFTER shutdown.[B-----]My leak caused a 2 cylinder miss, on initial start up & some water loss.
Bill Beenthere[/B]
 
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You keep saying it doesn’t fire? Does that mean electrically, or that when you short the cylinder out there is no change in the engine
 
Maybe 1 & 2 are cross firing in the distributor, so they are firing at the wrong time.


Use a vacuum gauge to check for sticking or slow to close valves.
 
Tom Wesenberg said:
Maybe 1 & 2 are cross firing in the distributor, so they are firing at the wrong time.


Use a vacuum gauge to check for sticking or slow to close valves.
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I'd do as Tom suggests, and use a vacuum gauge as a diagnostic tool. (Lots of sites onine showing what to look for.)

Most likely the head gasket is blown between those two cylinders. Before you install a new one, check block and head for flatness. You may be upping your CR a bit. ;)

PS. If you recently had the plug wires off, remember going CCW, the order is 1,2,4,3. Since 4 and 3 are for sure correct, perhaps 1 and 2 are reversed. It's easy to reverse them on a new style cap.
 
Its an old style distributer. The number one plug is at the far end of the arm, the number 2 is on the closer contact closest to the actual distributer cap body. I tested the compression last night and the pressure on the number 1 cylinder did force my hand off the plug port. Duh ! I did not check the number 2 plug to see if I got he same results. Is there a diagram somewhere that shows the old style distributer cap and which copper strip goes to which cylinder ?




Corley said:
I'd do as Tom suggests, and use a vacuum gauge as a diagnostic tool. (Lots of sites onine showing what to look for.)

Most likely the head gasket is blown between those two cylinders. Before you install a new one, check block and head for flatness. You may be upping your CR a bit. ;)

PS. If you recently had the plug wires off, remember going CCW, the order is 1,2,4,3. Since 4 and 3 are for sure correct, perhaps 1 and 2 are reversed. It's easy to reverse them on a new style cap.
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Check the wear in the distributor bushings. It can work good at firing, when the distributor is at rest, but when running, the shaft can wobble, and miss some cylinders. They work well, until they don't. If you can grab the shaft on top, under the rotor, and try to move it around, and if you get any kind of movement, that is always to much.


Thanks,


Herm.
 
This was my problem when the front two cylinders stopped firing.
 

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. Is there a diagram somewhere that shows the old style distributer cap and which copper strip goes to which cylinder ?[/QUOTE]

I don't think you can get them mixed up. The copper strip won't reach the wrong plug.
 
Update : I pulled the plugs last night and held my thumb over the plug port and disconnected the coil from the distributer cap. I had my best friend turn the engine over and I could not keep my thumb over the plug port. Felt vacunm and then upward pressure on both cylinders. the upstroke pressure was enough to move my thumb off. I am waiting for a bushing to arrive so that I can do a proper pressure check, but there was plenty of pressure on the poor mans pressure test.




DScott said:
I have a 29' Model A. It has been running great, and then it started running rough. Turns out the first two cylinders from front to back stopped firing. I checked distributer, and I am getting fire to the plugs, but they are not firing. Bought new plugs, set the gap, still not firing. Somebody told me the exhaust valves are notorious for sticking. Any ideas on how I can unstick these valves ? I tried spraying Marvel Mystery Oil down the carb while it was running, and that so far has not worked. Any help will be appreciated.
Click to expand...
 
DScott said:
I have a 29' Model A. It has been running great, and then it started running rough. Turns out the first two cylinders from front to back stopped firing. I checked distributer, and I am getting fire to the plugs, but they are not firing. Bought new plugs, set the gap, still not firing. Somebody told me the exhaust valves are notorious for sticking. Any ideas on how I can unstick these valves ? I tried spraying Marvel Mystery Oil down the carb while it was running, and that so far has not worked. Any help will be appreciated.
Click to expand...





Update. removed plugs turned engine over, plenty of pressure. waiting for bushing to do proper pressure test.
 
Update: Removed the two plugs last night, turned the engine over while holding my thumb on plug port. Both ports had plenty of pressure. Enough to move my thumb off on the upstroke. When the engine runs, I can pull the copper strip off the plug and see a very bright arc from the copper strip to the top of the plug, but when I pull it away from the plug, there is no drop in RPMS.
 
ryanheacox said:
This was my problem when the front two cylinders stopped firing.
Click to expand...


Did you go back with copper gaskets ? I was looking at the gasket sets online at Brattons, seems like a lot of gaskets in he head gasket set. Was that a pretty deep dive project ( head gaskets ) ?
 
Did you try another distributor body? That the black Bakelite part that sometimes shorts between 1 and 2 or 3 and 4. It shorts inside the Bakelite, where you can't see it. Best to just try another one.
 
DScott said:
Did you go back with copper gaskets ? I was looking at the gasket sets online at Brattons, seems like a lot of gaskets in he head gasket set. Was that a pretty deep dive project ( head gaskets ) ?
Click to expand...

Pretty sure what you were looking at is the entire engine gasket set which includes the head gasket. You only need the head gasket.

As far as changing a head gasket, the A is extremely easy compared to most cars. With enough practice I'd bet it can be done in an hour or less.

I ended up going for the "best" brand graphite head gasket but copper should work just fine too, it has for 90 years. I reused the water neck gasket.
 
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