Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 11-27-2018, 11:09 AM   #1
V4F
Senior Member
 
V4F's Avatar
 
Join Date: May 2010
Location: ca.
Posts: 2,522
Default Help please

1929 ford A pick up . mostly all stock (modern point plate) . driving along & big back fire . checked everything & can not find the problem . back fires occasionally thru carb , but has low power . things we have checked ….
1) points / timing
2) valves open / close
3) carb
4) distributor
5) moved spark lever different ways
6) it will run but not as before


checked these items several times . need new ideas please ……..
__________________
V4f
V4F is offline   Reply With Quote
Old 11-27-2018, 11:22 AM   #2
nick c
Senior Member
 
Join Date: Aug 2010
Posts: 260
Default Re: Help please

The big bang could be a bad electrical connection, it will allow raw gas to exit cylinder and enter exhaust manifold then when connection comes back you get the bang, a weak engine could be a weak condenser or a weak coil,
might do a compression check

carry on nick c
nick c is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 11-27-2018, 11:25 AM   #3
Will N
Senior Member
 
Will N's Avatar
 
Join Date: Jul 2010
Location: Pennsylvania
Posts: 1,096
Default Re: Help please

Check the little carbon dimple in the center of the distributor cap. I've personally seen two occasions were a car started running poorly, and after checking all the things you checked, it was found that the carbon dimple was cracked or missing. From now on, that will always be the first thing I check!
Will N is offline   Reply With Quote
Old 11-27-2018, 11:27 AM   #4
Kurt in NJ
Senior Member
 
Kurt in NJ's Avatar
 
Join Date: May 2010
Location: on the Littlefield
Posts: 6,132
Default Re: Help please

Condenser can cause such things-----
Kurt in NJ is offline   Reply With Quote
Old 11-27-2018, 11:44 AM   #5
monto
Senior Member
 
monto's Avatar
 
Join Date: Apr 2015
Location: NH
Posts: 182
Default Re: Help please

Also, could be fuel mixture too lean. ?
__________________
'30 Coupe
monto is offline   Reply With Quote
Old 11-27-2018, 12:06 PM   #6
art ebeling
Senior Member
 
art ebeling's Avatar
 
Join Date: Dec 2014
Location: Hillsboro IL
Posts: 478
Default Re: Help please

Sponsored Links (Register now to hide all advertisements)
It is running lean on gas, probably a blockage at the firewall or pencil filter in tank.. Start at the sediment bowl and work backwards to the gas tank. if you take a fuel line off you will most likely see the gas flow stop after a minute or so. You could verify by pulling out on the choke when the backfiring starts. Art
art ebeling is offline   Reply With Quote
Old 11-27-2018, 12:39 PM   #7
V4F
Senior Member
 
V4F's Avatar
 
Join Date: May 2010
Location: ca.
Posts: 2,522
Default Re: Help please

good ideas ……….….. forgot compression was weird … #1/4 65# #2/3 50# thanks & I will peruse it .
__________________
V4f
V4F is offline   Reply With Quote
Old 11-27-2018, 01:23 PM   #8
30 Closed Cab PU
Senior Member
 
Join Date: Aug 2018
Posts: 2,332
Default Re: Help please

My father had a lot of old tractors. He would use an old riding lawn mower gas tank with a shutoff on it, disconnect the gas line at the carb, drain the carb , clean the carb filter if it had one, and substitute the mower gas tank. Run the tractor awhile, if issue was gone he knew he had a fuel issue.
30 Closed Cab PU is offline   Reply With Quote
Old 11-27-2018, 01:37 PM   #9
MALAK
Senior Member
 
MALAK's Avatar
 
Join Date: Jun 2010
Location: Highland, CA
Posts: 207
Default Re: Help please

Quote:
Originally Posted by V4F View Post
good ideas ……….….. forgot compression was weird … #1/4 65# #2/3 50#
I'm guessing the head gasket is beginning to fail. When cyl 2 is on its power stroke cyl 3 is on its intake stroke and vice versa when cyl 2 is on intake cyl 3 is on power. If the hot gasses from either cylinder are crossing to the adjacent cyl the incoming air/fuel charge could be ignited. Resulting in a backfire through the carb.

Good luck,
Tom
MALAK is offline   Reply With Quote
Old 11-27-2018, 02:49 PM   #10
Bob C
Senior Member
 
Join Date: May 2010
Location: So Cal
Posts: 8,697
Default Re: Help please

The head gaskets don't usually fail between 2 & 3, there's a lot of meat there.
Bob C is offline   Reply With Quote
Old 11-27-2018, 03:35 PM   #11
Synchro909
Senior Member
 
Synchro909's Avatar
 
Join Date: Jun 2014
Location: Melbourne, Australia
Posts: 7,444
Default Re: Help please

Quote:
Originally Posted by MALAK View Post
I'm guessing the head gasket is beginning to fail. When cyl 2 is on its power stroke cyl 3 is on its intake stroke and vice versa when cyl 2 is on intake cyl 3 is on power. If the hot gasses from either cylinder are crossing to the adjacent cyl the incoming air/fuel charge could be ignited. Resulting in a backfire through the carb.

Good luck,
Tom
There was discussion in a thread here a while ago as to whether it is even possible for a backfire to happen through the carby. Some argued that a BACK fire would only be the explosion of unburnt gasses in the exhaust (ie, out of the back of the engine) and that a "cough" through the carby would be a FORWARD fire. I thought it an acedemic difference but it would at least be more accurate and avoid misunderstandings.
This post reminded me of it.
__________________
I'm part of the only ever generation with an analogue childhood and a digital adulthood.
Synchro909 is offline   Reply With Quote
Old 11-27-2018, 04:41 PM   #12
100IH
Senior Member
 
Join Date: Dec 2011
Location: SW Idaho
Posts: 970
Default Re: Help please

Does it idle smooth or does it sound like one is missing ? Short one at a time to see if one is dead by listening to the RPM drop off. This is called cylinder balance test. Takes 1 ear or 2 and a screwdriver. Where it backfires is important: tailpipe or carb. If guessing is the preferred diagnostic path way based on stories of others who don't understand diagnostic procedures : go back to original points and plate in the dist. In the ideal world, Your good list would tell what test you did and what were the results and NOT just say Carb, Dist, Valves move,. By the way, even smelling the tailpipe is good information. What you learn along the way is more important than just getting it to run better. Good luck. There is pretty much a test for everything that is necessary to run.

Last edited by 100IH; 11-27-2018 at 04:57 PM.
100IH is offline   Reply With Quote
Old 11-27-2018, 06:32 PM   #13
MALAK
Senior Member
 
MALAK's Avatar
 
Join Date: Jun 2010
Location: Highland, CA
Posts: 207
Default Re: Help please

Quote:
Originally Posted by Bob C View Post
The head gaskets don't usually fail between 2 & 3, there's a lot of meat there.
True that.

Quote:
Originally Posted by Synchro909 View Post
There was discussion in a thread here a while ago as to whether it is even possible for a backfire to happen through the carby. Some argued that a BACK fire would only be the explosion of unburnt gasses in the exhaust (ie, out of the back of the engine) and that a "cough" through the carby would be a FORWARD fire. I thought it an acedemic difference but it would at least be more accurate and avoid misunderstandings.
This post reminded me of it.
Quote:
Originally Posted by V4F View Post
back fires occasionally thru carb
Interesting.
If we consider the fuel/air mix entering the cylinder as Forward flow wouldn't a reversal of that flow be considered a Back fire and an explosion in the exhaust, which flows the same direction as the exhaust, be considered a Forward fire? Or, in this discussion, were they looking at it from a perspective view? That is the intake (carb) is ahead of the exhaust and therefore Forward?
Personally, to avoid misunderstandings, when discussing these sorts of things I think the term backfire is appropriate but should be delineated as the OP said "back fires occasionally thru carb". No ambiguity there. At least in my mind.
MALAK is offline   Reply With Quote
Old 11-27-2018, 07:05 PM   #14
V4F
Senior Member
 
V4F's Avatar
 
Join Date: May 2010
Location: ca.
Posts: 2,522
Default Re: Help please

I will send a copy of these to my friend . thank you much …………. any new ideas appreciated
__________________
V4f
V4F is offline   Reply With Quote
Old 11-27-2018, 07:10 PM   #15
Tom Wesenberg
Senior Member
 
Tom Wesenberg's Avatar
 
Join Date: May 2010
Location: Mpls, MN
Posts: 27,582
Default Re: Help please

Maybe we can call a firing through the carb a "front fire".


It would be rare, but a backfire could damage the exhaust or muffler baffle, and might cause an exhaust blockage. This will be noted by a smooth idle, but not revving up as it should, and the manifold vacuum will drop very low at open throttle. If you hold your hand at the tailpipe, you should feel a strong blast of exhaust when someone snaps the throttle open.


In the 70's and 80's I had to repair a few exhaust with double wall pipes, where the inner layer collapsed, and couldn't be seen blocking the exhaust flow.
Tom Wesenberg is offline   Reply With Quote
Old 11-27-2018, 09:19 PM   #16
Paul Bjarnason
Senior Member
 
Join Date: Jul 2018
Location: Annandale, VA
Posts: 150
Default Re: Help please

I would check for carbon tracks in the distributor cap. This has happened to me more than once. The tracks are hard to see, but will allow spark which is supposed to go to one cylinder to go to the wrong place.
Paul Bjarnason is offline   Reply With Quote
Old 11-28-2018, 09:23 AM   #17
V4F
Senior Member
 
V4F's Avatar
 
Join Date: May 2010
Location: ca.
Posts: 2,522
Default Re: Help please

paul , we have checked & cleaned ……… thank you
__________________
V4f
V4F is offline   Reply With Quote
Old 11-28-2018, 10:02 AM   #18
saintjoelarry
Junior Member
 
Join Date: Nov 2011
Location: Grand Rapids, MI
Posts: 25
Default Re: Help please

Quote:
Originally Posted by Tom Wesenberg View Post
Maybe we can call a firing through the carb a "front fire".


It would be rare, but a backfire could damage the exhaust or muffler baffle, and might cause an exhaust blockage. This will be noted by a smooth idle, but not revving up as it should, and the manifold vacuum will drop very low at open throttle. If you hold your hand at the tailpipe, you should feel a strong blast of exhaust when someone snaps the throttle open.


In the 70's and 80's I had to repair a few exhaust with double wall pipes, where the inner layer collapsed, and couldn't be seen blocking the exhaust flow.
Certainly checking the conensor is a great idea, but I would certainly listen to Tom. His advise to me a while back was spot on - baffles had come loose in aftermarket muffler, causing blockage. Car ran great at idle, but no power and backfiring when under power.
saintjoelarry is offline   Reply With Quote
Old 11-28-2018, 12:37 PM   #19
Farrell In Vancouver
Senior Member
 
Farrell In Vancouver's Avatar
 
Join Date: May 2010
Location: Pitt Meadows BC
Posts: 1,003
Default Re: Help please

Might pull the instrument panel and check the tightness of the ignition switch wires.
Farrell In Vancouver is offline   Reply With Quote
Old 11-28-2018, 12:58 PM   #20
Purdy Swoft
Senior Member
 
Purdy Swoft's Avatar
 
Join Date: May 2010
Location: Alabama
Posts: 8,099
Default Re: Help please

I would chande back to original points and condenser .
Purdy Swoft is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 01:50 AM.