Early Ford V-8 Club Forum

EFV-8 Club Forum / General Ford Discussion / carburetor adjustment screw not working

Reply to Discussion | New Discussion << previous || next >>

Posted By Discussion Topic: carburetor adjustment screw not working -- page: 1 2     Wolfie 12-26-2009 @ 4:41 PM reply profile send p.m. New Member Posts: 144 Joined: Oct 2009 My car ran rough today and when I got home I tried to adjust the carburetor. I found that the right screw doesn't do anything, even when I screw it all the way in. The left screw works ok. What may be the problem with the right screw? 1940 Ford. Thanks! ford38v8 12-26-2009 @ 6:18 PM reply profile send p.m. Senior Posts: 2758 Joined: Oct 2009 Wolfie, Whatever the cause of your engine running rough, there is no adjustment of your carburetor to address that issue, and we'll need further information to diagnose that problem. The two screws you did try to adjust are only for the idle, and do not appreciably affect how your engine runs while driving. These screws are needle valves, and adjust the amount of fuel that is sucked into the throat of your carb at idle. To check on their condition, unscrew them all the way out, being careful to retain the springs as they come out. They should both be straight, pointed sharply on the ends, and with no indication of having been screwed in tightly with a screwdriver. Screw them both in all the way by hand, and turn them out 3/4 turn for now, and we'll try to help you get your engine to run well before adjusting them properly. Alan Wolfie 12-26-2009 @ 7:40 PM reply profile send p.m. New Member Posts: 144 Joined: Oct 2009 Thanks Alan. I had thought I was adjusting the fuel mixture by adjusting those screws. Guess I have something else going on. There is still something wrong with the right adjusting screw. I have taken it out and it has no evidence of being scored with tightening. And it has no effect on the idle by turning. ford38v8 12-26-2009 @ 9:12 PM reply profile send p.m. Senior Posts: 2758 Joined: Oct 2009 Wolfie, OK, good. So replace the needles and adjust as I said previously. Never adjust anything in an attempt to correct an unknown problem, as you likely will introduce another problem in so doing, making diagnosis very difficult. One problem at a time is all any mechanic can deal with. Next, check for spark at all the plugs individually. Remove the plug wire from each plug, and check for a good strong blue spark against a head bolt. Hold the insulated wire, not the hot end. Hold each against the spark plug to detect a change in motor rhythm. If that all goes well, then next we can check the fuel system. One thing at a time. Alan TomO 12-28-2009 @ 12:28 PM reply profile send p.m. Senior Posts: 7250 Joined: Oct 2009 Your carburetor has a problem in the idle passages. I would remove the carburetor from the car and clean the idle tubes and passages. Spray carb cleaner into the main jets, the idle tubes and the passages in the carb body and the carb base. Make sure that the cleaner comes out of both the holes above the throttle plate and the holes below the throttle plate. Make sure that you use the correct gasket between the base of the carburetor and the body. The kits cover the carburetor from 1938 -1955. The post 1948 carburetor uses different gaskets than the pre 48 carburetor and will block the idle passages. This should allow both idle air adjustment screws to affect the idle mixture. Tom supereal 12-28-2009 @ 1:40 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Also, check for a vacuum leak. Many times we find a wiper hose has cracked or has fallen off the fitting on the intake, or the vacuum line to the distributor is leaking. If the problem came on gradually, and changes as you drive, look at the throttle shaft in the carb. If you feel ANY play, it must be bushed to eliminate vacuum loss. Another cause of rough running is leaking plug wires, either in the metal loom tubes, or at the ends, if they have not been soldered on, or are non-metallic "wires". Any of these faults can make the idle screws seem ineffective. Wolfie 12-28-2009 @ 4:50 PM reply profile send p.m. New Member Posts: 144 Joined: Oct 2009 Tomorrow will be my old car day. Very good experienced recommendations from Alan, Tom, and Super. I will check for a vacuum leak first then take off the carb and clean the idle passages. I just replaced my fuel tank and some rust may have made it's way to the carb and blocked one passage. Thanks! Wolfie 12-29-2009 @ 5:35 PM reply profile send p.m. New Member Posts: 144 Joined: Oct 2009 I checked my vacuum line and it is very soft at the carb but not leaking and I'll change it soon. Then I removed the carb, took it apart and sprayed carb cleaner as Tom recommended. It worked and both idle adjustment screws work. I will take it for a drive tomorrow and see and see how it runs but it seems great. It definately isn't as rough running as it had been. Thanks! supereal 12-30-2009 @ 7:00 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Install an inline filter between the tank and the firewall to catch the debris, and prevent another clogged carb. Wolfie 12-30-2009 @ 5:09 PM reply profile send p.m. New Member Posts: 144 Joined: Oct 2009 Installing a second fuel filter would be a good idea. Super said between the tank and the firewall. Are you recommending it be under the car so it won't be visable or did you mean just before the existing fuel filter. My filter is the type with glass bowl with replacable cartridge which I thought worked pretty good.

<< previous || next >>

PAGE: 1 2

NOTE: YOU MUST BE A REGISTERED USER AND BE LOGGED IN TO POST (and reply to) messages in this forum. If you are a first time user, please click the CREATE A NEW ACCOUNT in the masthead above to register and Log In. After that, all you do is LOG IN to enjoy using this site.

DISCLAIMER: The V-8 Club does no independent testing of any of the opinions, thoughts or suggestions presented in the website on the Forum, in the Tech Tips section, or any section. A reader should consider the website to be a forum wherein differing solutions to a particular set of circumstances may be discussed. Ultimately, the selection of an item for an individual's vehicle must be based upon the independent study of the vehicle owner in consultation with people in the hobby and restoration experts.

EFV-8 Club Forum Home | Back to Home Page | Contact the Webmaster

Copyright © 2009 - EFV-8.org
Powered by < CF FORUM > v.2.1