The Ford Barn

tyler · 04-13-2013, 06:28 AM

Got my electrical problems fixed, buttoned everything back up and to my amazment, the car started. Thought I' let it run for a while as it hasn't been run all winter. Started it with the gav open a little less than three quarters turn, after it warmed up a bit, closed the gav to 1/4 turn, where it normally runs well when warm. Was running fine but after 5 minutes or so it started running rough and to smooth it out, I had to OPEN the gav 3/4 turn.
What would cause this and what can I do to fix it? All stock setup, carb rebuilt last year.
Thanks

Tyler

tdlmomowers · 04-13-2013, 07:26 AM

Opening the GAV, riches the mixture, so it sound like the Carb. was leaning out. Check your Carb. and see if the main jet is getting clogged up with something. The Zenith Carb. is very easy to clean and blow out all the passages. The new gas with ethanol is bad to leave deposits in the float bowl. I redid a Carb. last year the looked like it was full of baking soda. I soaked the Carb.in white vinegar for a few hours and it cleaned up really nice and worked great.

Gary WA · 04-13-2013, 09:38 AM

Has the car been sitting for the winter?? check your points for winter residue!

steve s · 04-13-2013, 10:05 AM

Starting to run rough after warmup can be due to premature fuel vaporization (fighting words) or thermal expansion either opening up a vacuum leak or creating a poor electrical connection. The fact that opening the GAV cured it, eliminates the last one but leaves the first two, IF the behavior is reproducible after car sits over night again.

If it runs rough from the get-go the next time you start it, I would suspect a piece of crud has found its way into one of the carb jets. Try the carburetor Heimlich: momentarily race motor via throttle shaft while simultaneously completely covering carb air intake with palm of hand and then quickly pulling it away before motor dies. Probably smart to wear a glove in case of backfire. The tremendous vacuum created by racing the motor WILL pull anything caught in the jets on through. Might have to repeat a few times.

Steve

Bill in Al · 04-13-2013, 01:43 PM

When mine acts that way I find it's usually the in- carb filter and take it out,blow through it and it's ok then. Only happens when about 1/4 or less in the tank. I know,I know! I need to clean the tank!

Contenderizer · 04-13-2013, 01:44 PM

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Also, check for a vacuum leak.

tyler · 04-13-2013, 03:30 PM

I'll try all your suggestions in the morning and see what happens. I'll report back with my findings. Thanks again, guys.

Tyler

ctlikon0712 · 04-13-2013, 08:23 PM

Contenderizer, that was what I was going to say also. Once she is warmed up and expanded it sounds like a vacuum leak developed hence the need to correct the A/F ratio.... check the throttle plate shaft area, carb to intake gasket, intake to block gasket and possibly the vacuum wiper and associated lines.

tyler · 04-14-2013, 07:45 AM

O.K., what's the best way to check for a vacuum leak and where is the throttle plate shaft? I put all new manifolds and gaskets on the engine last summer, was very carefull to make sure everything snugged up several times after running the car some. Don't have a vacuume wiper so that's out. Thanks again.

Tyler

Tom Wesenberg · 04-14-2013, 08:01 AM

Quote:

Originally Posted by tyler

O.K., what's the best way to check for a vacuum leak and where is the throttle plate shaft? I put all new manifolds and gaskets on the engine last summer, was very carefull to make sure everything snugged up several times after running the car some. Don't have a vacuume wiper so that's out. Thanks again.

Tyler

The throttle shaft is connected to the arm, which connects to the linkage on back to the gas pedal.

To check for a vacuum leak I like to use a propane torch UNLIT. Just turn the torch valve open a little and use it to sniff around the carb and manifold. If there is a leak, it will suck in the propane and make the engine run faster and smoother.

ctlikon0712 · 04-14-2013, 05:16 PM

Pages 8-10 of this wonderful PDF by Tom Endy, covers the throttle shaft area and how to fix if it is the problem.
http://www.ocmafc.org/techarticles/T...%2011-2007.pdf
What happens is the shaft eventually wears an elongated hole in the casting. This sucks air, bypassing the metering effects the carb was designed to do and makes for a lean mixture. The fix is to re bushing the casting.

ba49 · 04-14-2013, 07:08 PM

Check your condenser. Mine acted exactly like that and it turned out to be the condenser.

04-13-2013, 06:28 AM	#1
tyler Senior Member Join Date: Aug 2010 Location: Randolph N.Y. Posts: 105	What would cause this...carburator Got my electrical problems fixed, buttoned everything back up and to my amazment, the car started. Thought I' let it run for a while as it hasn't been run all winter. Started it with the gav open a little less than three quarters turn, after it warmed up a bit, closed the gav to 1/4 turn, where it normally runs well when warm. Was running fine but after 5 minutes or so it started running rough and to smooth it out, I had to OPEN the gav 3/4 turn. What would cause this and what can I do to fix it? All stock setup, carb rebuilt last year. Thanks Tyler

04-13-2013, 07:26 AM	#2
tdlmomowers Senior Member Join Date: May 2010 Location: Mansfield, Ohio Posts: 409	Re: What would cause this...carburator Opening the GAV, riches the mixture, so it sound like the Carb. was leaning out. Check your Carb. and see if the main jet is getting clogged up with something. The Zenith Carb. is very easy to clean and blow out all the passages. The new gas with ethanol is bad to leave deposits in the float bowl. I redid a Carb. last year the looked like it was full of baking soda. I soaked the Carb.in white vinegar for a few hours and it cleaned up really nice and worked great.

04-13-2013, 09:38 AM	#3
Gary WA Senior Member Join Date: May 2010 Location: Clinton,WA/Whidbey Island Posts: 4,101	Re: What would cause this...carburator Has the car been sitting for the winter?? check your points for winter residue! __________________ www.whidbeymodelaclub.com

04-13-2013, 10:05 AM	#4
steve s Senior Member Join Date: May 2010 Location: Kalamazoo Posts: 1,656	Re: What would cause this...carburator Starting to run rough after warmup can be due to premature fuel vaporization (fighting words) or thermal expansion either opening up a vacuum leak or creating a poor electrical connection. The fact that opening the GAV cured it, eliminates the last one but leaves the first two, IF the behavior is reproducible after car sits over night again. If it runs rough from the get-go the next time you start it, I would suspect a piece of crud has found its way into one of the carb jets. Try the carburetor Heimlich: momentarily race motor via throttle shaft while simultaneously completely covering carb air intake with palm of hand and then quickly pulling it away before motor dies. Probably smart to wear a glove in case of backfire. The tremendous vacuum created by racing the motor WILL pull anything caught in the jets on through. Might have to repeat a few times. Steve Last edited by steve s; 04-14-2013 at 10:03 AM.

04-13-2013, 01:43 PM	#5
Bill in Al Senior Member Join Date: May 2010 Location: Pell City (New London) Al Posts: 317	Re: What would cause this...carburator When mine acts that way I find it's usually the in- carb filter and take it out,blow through it and it's ok then. Only happens when about 1/4 or less in the tank. I know,I know! I need to clean the tank!

04-13-2013, 01:44 PM	#6
Contenderizer Junior Member Join Date: Feb 2012 Location: N Central Florida Posts: 23	Re: What would cause this...carburator Sponsored Links (Register now to hide all advertisements) Also, check for a vacuum leak.

04-13-2013, 03:30 PM	#7
tyler Senior Member Join Date: Aug 2010 Location: Randolph N.Y. Posts: 105	Re: What would cause this...carburator I'll try all your suggestions in the morning and see what happens. I'll report back with my findings. Thanks again, guys. Tyler

04-13-2013, 08:23 PM	#8
ctlikon0712 Senior Member Join Date: Feb 2011 Location: Cocoa, Florida Posts: 1,609	Re: What would cause this...carburator Contenderizer, that was what I was going to say also. Once she is warmed up and expanded it sounds like a vacuum leak developed hence the need to correct the A/F ratio.... check the throttle plate shaft area, carb to intake gasket, intake to block gasket and possibly the vacuum wiper and associated lines. __________________ Wanted: Simmons Super Power Head Craig Likon 1931 150B

04-14-2013, 07:45 AM	#9
tyler Senior Member Join Date: Aug 2010 Location: Randolph N.Y. Posts: 105	Re: What would cause this...carburator O.K., what's the best way to check for a vacuum leak and where is the throttle plate shaft? I put all new manifolds and gaskets on the engine last summer, was very carefull to make sure everything snugged up several times after running the car some. Don't have a vacuume wiper so that's out. Thanks again. Tyler

04-14-2013, 05:16 PM	#11
ctlikon0712 Senior Member Join Date: Feb 2011 Location: Cocoa, Florida Posts: 1,609	Re: What would cause this...carburator Pages 8-10 of this wonderful PDF by Tom Endy, covers the throttle shaft area and how to fix if it is the problem. http://www.ocmafc.org/techarticles/T...%2011-2007.pdf What happens is the shaft eventually wears an elongated hole in the casting. This sucks air, bypassing the metering effects the carb was designed to do and makes for a lean mixture. The fix is to re bushing the casting. __________________ Wanted: Simmons Super Power Head Craig Likon 1931 150B

04-14-2013, 07:08 PM	#12
ba49 Senior Member Join Date: Jun 2012 Location: Sheffield Lake, Ohio Posts: 137	Re: What would cause this...carburator Check your condenser. Mine acted exactly like that and it turned out to be the condenser.