The Ford Barn

'31 Patina · 06-26-2011, 04:30 PM

I have a '31 coupe with the original 4 banger motor in it. I went to start it yesterday and two of the cylinders are not firing. I pulled the plugs and found the two plugs closest to the firewall are black and dry. The two front ones are still shinny and wet with gas. So I assume these two cylinders are not firing as the car is running rough.

I'm new to the model A motor so what are some of the things I should be looking at to correct this problem? I plan on doing a compression test but before I do so I was wondering what type of compression readings are normal? Also could this problem be within the distributor? I've owned the car for a year and never rebuilt the distributor. I'm not sure what or if anything the previous owner did with the distributor.

Thanks for the help!

ford1 · 06-26-2011, 04:37 PM

do a quick compression check on all cylinders if all are above #60 engine is probably ok ,clean or replace plugs and see if it starts sounds like the carb is running rich, but you wont know till its running, come back and tell us what you have found

John Duden · 06-26-2011, 04:43 PM

check the distrubter cover, i had a wire inside of the wings short out and would not fire, but then again change the spark plugs, the spring in the insulator of the plug may be burned out
John

'31 Patina · 06-26-2011, 04:53 PM

Quote:

Originally Posted by ford1

do a quick compression check on all cylinders if all are above #60 engine is probably ok ,clean or replace plugs and see if it starts sounds like the carb is running rich, but you wont know till its running, come back and tell us what you have found

Thanks for the info. I plan on doing a compression test this week sometime and I'm hoping the engine is okay. The spark plugs are new. Not only was the bottom of the front two spark plugs wet but when I looked inside the the spark plug hole I found that too was wet with gas where the other two holes were dry.

I also noticed when I let the car idle the rear part of the exhaust manifold, the two cylinders that are firing, is hot and much darker in color compared to the front half of the manifold which is cooler and lighter in color which I assume is because the first two cylinders are not firing.

IrishHills · 06-26-2011, 07:12 PM

Do you have spark to the two that are not firing? (disconect wires from plug and leave about a 1/4 to 1/2" away, crank motor, spark jump?) if so you might want to turn the motor over with plugs out to dry cylinders and dry the plugs with heat, may be just a flooding problem.

'31 Patina · 06-26-2011, 09:00 PM

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Quote:

Originally Posted by IrishHills

Do you have spark to the two that are not firing? (disconect wires from plug and leave about a 1/4 to 1/2" away, crank motor, spark jump?) if so you might want to turn the motor over with plugs out to dry cylinders and dry the plugs with heat, may be just a flooding problem.

I do have spark to the two spark plugs that are not firing. I disconnected the wires from the plug and held it away about 1/4" and had spark.

If it's flooded would it cause two cylinders not to fire?

'31 Patina · 06-26-2011, 09:04 PM

Quote:

Originally Posted by Ed

If you find the compression is good, then check for cracks in the distributor body. I have had a few problems with the reproduction distributor bodies in the past.

Good luck, and thanks for sharing your Model A problems with us. We all learn from each other.

I'll be doing a compression test this week so I'll share my results when finished.

Thanks to everyone for their input.

Mitch//pa · 06-26-2011, 09:37 PM

possible vacuum leak at the intake gaskets to those cylinders...

'31 Patina · 06-26-2011, 09:49 PM

Quote:

Originally Posted by Mitch//pa

possible vacuum leak at the intake gaskets to those cylinders...

I recently replaced the exhaust manifold because the old one had a crack in it. I snugged up the nuts but I'm wondering if I should sung them up some more after I've had it running? Would that cause enough of a vacuum leak to not fire two cylinders if the nuts were not tight enough? I just don't want to crack the ears on the manifold.

Thanks for the input.

Tom Wesenberg · 06-26-2011, 09:57 PM

"If it's flooded would it cause two cylinders not to fire?"
YES

Swap the front 2 plugs with the 2 rear cylinders and see what happens. Heating the plug with a propane torch should clear them up for use.

Milton · 06-26-2011, 10:31 PM

Quote:

Originally Posted by '31 Patina

I recently replaced the exhaust manifold because the old one had a crack in it. I snugged up the nuts but I'm wondering if I should sung them up some more after I've had it running? Would that cause enough of a vacuum leak to not fire two cylinders if the nuts were not tight enough? I just don't want to crack the ears on the manifold.

Thanks for the input.

When the manifold was changed did you bolt the intake and exhaust together at the heat transfer and check for flatness across the ports?

Patrick L. · 06-27-2011, 08:14 AM

Like has been said, it kinda sounds like you may some severely fouled sparklers, defective head gasket or a vacuum leak.. A compression check is in order and all cylinders should read about 45#-60# and be within 5# of each other.. If the 2 adjacent cylinders are low then you could have a bad head gasket, split cylinder/block or head.. If the compression is OK then I too would suspect a vacuum leak.. Lay a straight edge across the manifolds and if there is more than about .010" gap anywhere then they should be cut..

'31 Patina · 06-28-2011, 09:52 PM

Here's an update on my situation. I checked compression of all cylinders and I found that I had no compression at all on the first cylinder. I pulled the head to take a look and found that the head of the piston was shattered. I don't know when or how this happened. I haven't had it on the road yet this season as I've been doing other things to it. I've had it running numerous times this spring (idling) but never heard any knocking or unusual noise. I did notice that when I started it this past weekend it idled very fast and the engine got very hot within two minutes. I turned it off and that's when I noticed one of the cylinders wasn't firing. What would cause the piston to shatter? Could the timing or the spark control lever have something to do with it if it wasn't set correctly? I'm just trying to figure out if I did something wrong while letting it idle the few times.

Thanks.

06-26-2011, 04:30 PM	#1
'31 Patina Senior Member Join Date: Jul 2010 Location: Rosemount, MN Posts: 228	Two Cylinders Not Firing I have a '31 coupe with the original 4 banger motor in it. I went to start it yesterday and two of the cylinders are not firing. I pulled the plugs and found the two plugs closest to the firewall are black and dry. The two front ones are still shinny and wet with gas. So I assume these two cylinders are not firing as the car is running rough. I'm new to the model A motor so what are some of the things I should be looking at to correct this problem? I plan on doing a compression test but before I do so I was wondering what type of compression readings are normal? Also could this problem be within the distributor? I've owned the car for a year and never rebuilt the distributor. I'm not sure what or if anything the previous owner did with the distributor. Thanks for the help!

06-26-2011, 04:37 PM	#2
ford1 Senior Member Join Date: May 2010 Location: oroville ca. Posts: 1,554	Re: Two Cylinders Not Firing do a quick compression check on all cylinders if all are above #60 engine is probably ok ,clean or replace plugs and see if it starts sounds like the carb is running rich, but you wont know till its running, come back and tell us what you have found

06-26-2011, 04:43 PM	#3
John Duden Senior Member Join Date: Jun 2010 Posts: 1,854	Re: Two Cylinders Not Firing check the distrubter cover, i had a wire inside of the wings short out and would not fire, but then again change the spark plugs, the spring in the insulator of the plug may be burned out John

06-26-2011, 07:12 PM	#5
IrishHills Senior Member Join Date: Sep 2010 Location: Brooklyn, Michigan "Home of M.I.S." Posts: 398	Re: Two Cylinders Not Firing Do you have spark to the two that are not firing? (disconect wires from plug and leave about a 1/4 to 1/2" away, crank motor, spark jump?) if so you might want to turn the motor over with plugs out to dry cylinders and dry the plugs with heat, may be just a flooding problem.

06-26-2011, 09:37 PM	#8
Mitch//pa BANNED Join Date: May 2010 Location: Bucks County, PA Posts: 11,454	Re: Two Cylinders Not Firing possible vacuum leak at the intake gaskets to those cylinders...

06-26-2011, 09:57 PM	#10
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Two Cylinders Not Firing "If it's flooded would it cause two cylinders not to fire?" YES Swap the front 2 plugs with the 2 rear cylinders and see what happens. Heating the plug with a propane torch should clear them up for use.

06-27-2011, 08:14 AM	#12
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: Two Cylinders Not Firing Like has been said, it kinda sounds like you may some severely fouled sparklers, defective head gasket or a vacuum leak.. A compression check is in order and all cylinders should read about 45#-60# and be within 5# of each other.. If the 2 adjacent cylinders are low then you could have a bad head gasket, split cylinder/block or head.. If the compression is OK then I too would suspect a vacuum leak.. Lay a straight edge across the manifolds and if there is more than about .010" gap anywhere then they should be cut..

06-28-2011, 09:52 PM	#13
'31 Patina Senior Member Join Date: Jul 2010 Location: Rosemount, MN Posts: 228	Re: Two Cylinders Not Firing Here's an update on my situation. I checked compression of all cylinders and I found that I had no compression at all on the first cylinder. I pulled the head to take a look and found that the head of the piston was shattered. I don't know when or how this happened. I haven't had it on the road yet this season as I've been doing other things to it. I've had it running numerous times this spring (idling) but never heard any knocking or unusual noise. I did notice that when I started it this past weekend it idled very fast and the engine got very hot within two minutes. I turned it off and that's when I noticed one of the cylinders wasn't firing. What would cause the piston to shatter? Could the timing or the spark control lever have something to do with it if it wasn't set correctly? I'm just trying to figure out if I did something wrong while letting it idle the few times. Thanks.