| Wolfie | -- 12-26-2009 @ 4:41 PM |
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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!
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| ford38v8 | -- 12-26-2009 @ 6:18 PM |
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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
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| Wolfie | -- 12-26-2009 @ 7:40 PM |
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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.
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| ford38v8 | -- 12-26-2009 @ 9:12 PM |
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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
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| TomO | -- 12-28-2009 @ 12:28 PM |
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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
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| supereal | -- 12-28-2009 @ 1:40 PM |
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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.
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| Wolfie | -- 12-28-2009 @ 4:50 PM |
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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!
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| Wolfie | -- 12-29-2009 @ 5:35 PM |
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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!
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| supereal | -- 12-30-2009 @ 7:00 AM |
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Install an inline filter between the tank and the firewall to catch the debris, and prevent another clogged carb.
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| Wolfie | -- 12-30-2009 @ 5:09 PM |
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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.
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| TomO | -- 12-31-2009 @ 7:05 AM |
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Any fuel filter should be installed before the fuel pump and you should not need more than one filter in the system. Because you had the idle passages plugged and carburetor cleaner helped you out, your filter may not be doing the job. Some of the older style filters did not trap the finer particles of debris and allow them to pass on to the fuel pump or carburetor where they cause problems. You might try installing a disposable filter after your current filter to check the effectiveness of your current filter. You could also just replace the current filter with a modern paper filter. Tom This message was edited by TomO on 12-31-09 @ 7:05 AM
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| supereal | -- 12-31-2009 @ 11:23 AM |
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We use the common "Fram" type inline filters, either metal or plastic. Cut the fuel line somewhere along the frame rail, and insert the filter, using the "worm gear" clamps on the rubber hose sections, not the spring type. Buy two filters so you can change along the road, if need be. We secure the filter to the frame with a couple of "Ty-Raps". Be sure to observe the markings on the filters as to flow direction.
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