Can't get engine to idle down

L

Lukes31a

Junior Member
After a decent amount of work I successfully put the engine in and got it hooked up. When I bought my late 31 tudor it came with and extra whats supposed to be a rebuilt model a engine. However, upon starting it up it revs up to what seems like full throttle. Once running if the choke is pulled out it will lower the rpms until finally it will kill the engine once its fully pulled out. I took out the carb and opened it to adjust the float to the correct distance from the machined edge. Checked valves and saw they were not stuck, then lubricated them to make sure of no problems.
I'm still learning as much as I can and just don't understand what could be the problem. Sucking in air somewhere? Fuel issue?
Thanks, Luke.
 
Disconnect the linkage from the carburetor and see if the throttle closes! You may have bent the linkage removing/ installing your engine. You could hold the arm on the carburetor closed with a spring and start it up adjust the carburetor idle.
 
Hello Luke, if your engine is running to high at idle position, it means that the throttle plate at the outlet of the carb is not closed, allowing gas to flow from the main jet into the engine. The throttle plate should be almost closed which forces the Idle jet to be the only jet putting fuel into the engine. Note that you should back out the idle speed screw to get the throttle plate closed. Ed
 
W/the idle adjustment screw backed out, check that the throttle plate closes all the way.
 
I forgot to mention, I disconnected the linkage already and checked the throttle plate and know that it does moves and had a buddy close it by hand and it still is basically full throttle. As well I have backed the idle screw back until it is almost about to fall out with no luck at dropping the rpms
 
Last edited:
Due to my accelerator return spring being broken the linkage isn't hooked up I have a buddy that sits and holds the throttle by hand. Even with the throttle closed all the way it still is in high rpms.
 
Lukes31a said:
I forgot to mention, I disconnected the linkage already and checked the throttle plate and know that it does moves and had a buddy close it by hand and it still is basically full throttle. As well I have backed the idle screw back until it is almost about to fall out with no luck at dropping the rpms
Click to expand...
This makes no sense. It's not possible for the throttle plate to be closed and to have the engine running at full throttle. Does your friend know which way to turn the throttle to close it versus opening it? I'm with BigHammer on this. The linkage is bent, preventing the throttle from closing.
 
Check for vacuum/air leaks. I recently had a carburetor (a brand new Zenith, no less!!) with excessive throttle shaft clearance that I was having high idle problems with. An oversize shaft cured the problem.

Check all intake gaskets also.

After thought; Check your plugs. Mine were white it was running so lean from above mentioned air leak. This will confirm you have an air leak somewhere.
 
Last edited:
Y-Blockhead said:
Check for vacuum/air leaks. I recently had a carburetor (a brand new Zenith, no less!!) with excessive throttle shaft clearance that I was having high idle problems with. An oversize shaft cured the problem.

Check all intake gaskets also.

After thought; Check your plugs. Mine were white it was running so lean from above mentioned air leak. This will confirm you have an air leak somewhere.
Click to expand...

When I get back on it tonight ill look for air leaks, as far as my plugs go they're about the opposite. They're pretty blackened.
 
Crazy question, but did you check the carb to make sure there is a throttle plate on the arm your friend is turning? If so, take a look at it and see if it closes completely. I don't see how it can run full throttle if the throttle plate is in place and fully closed.
 
Two thoughts:
1. May be the dumb one, but there are two plates, the throttle and the choke. Be sure they both close and open. Choke open and throttle closed.
2. The throttle plate has a bevel cut in it to thoroughly close. It will go on both ways, but not close tight if it is put on backwards (upside down). Look at the throttle plate from the top of the carb and be sure the bevel is turned the right way and it it closing completely.
 
I would be checking for:

Throttle plate not closed
Linkage bent preventing the throttle plate from closing
Idle adjust screw not properly adjusted.
 
Alright ill pull the carb tonight and do some looking around and take in all your suggestions and give you all an update. Thank you!
 
UPDATE: I cannot even express the disappointment in my friend I had helping me with the car... I was going to make an excuse so I didn't sound like and absolutely goon but long story shot he was holding the throttle wide open thinking he was holding it closed. So I thank you all for the advise and will definitely be back on if I run into another REAL problem. Thank you all ��
 
Where are you located? We can help you find a local club or even local experienced Model A guys. But we need your location. Put it in your avatar. It’s very helpful to have local experienced Model A friends. These cars are 90+ years old. They’re not complex, but maintenance requires specialized and experienced knowledge.
 
Lukes31a said:
UPDATE: I cannot even express the disappointment in my friend I had helping me with the car... I was going to make an excuse so I didn't sound like and absolutely goon but long story shot he was holding the throttle wide open thinking he was holding it closed. So I thank you all for the advise and will definitely be back on if I run into another REAL problem. Thank you all
Click to expand...


Oh, that’s funny. Sad, but funny.


Sent from my iPhone using Tapatalk
 
You must log in or register to reply here.
Back
Top