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EFV-8 Club Forum / General Ford Discussion / RPM slows down

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Posted By Discussion Topic: RPM slows down -- page: 1 2     46coupe 02-16-2024 @ 7:36 AM reply profile send p.m. Member Posts: 271 Joined: Oct 2015 HI everyone, My 46 Ford had been running perfectly. Now after the engine is warm and running smoothly the engine rpm starts going down unless I tap the gas pedal. Quite the challenge on a hill when the engine dies and trying to restart it. The engine dies on level ground as well. A friend of mine who works on these stated that the new gas, even the 100% none ethanol has additives in it that will settle in the bottom of the carb and start blocking the jets. This occurs because the car isn't driven that much. I try to drive it once or twice a month year round for 15-20 miles. If this is true is there anything I can use to clean out the carb without tearing it down? TomO 02-16-2024 @ 10:43 AM reply profile send p.m. Senior Posts: 7253 Joined: Oct 2009 I have not experienced that in my cars. If that is your problem, a can of Seafoam in a full tank of gas should clean it out. From my experience, I would suspect that the engine is getting flooded. An easy check is to look down the throat of the carburetor when the eng9ine is idling. If you see fuel dripping into the throat, flooding is your problem. The flooding could be due to float setting change or power valve leaking. Tom carcrazy 02-16-2024 @ 12:55 PM reply profile send p.m. Senior Posts: 1659 Joined: Oct 2009 Your problem may be caused by something in the ignition system. Once up to operating temperature, the coil and/or the condenser may be failing. Is your fuel tank properly vented? When the engine is exhibiting this problem, try removing the gas cap to see if the issue goes away. Something may be choking off air flow either going into or out of the engine. Try removing the air cleaner to see if the problem clears up. The exhaust pipe or muffler may have some debris blocking it. 46coupe 02-16-2024 @ 1:48 PM reply profile send p.m. Member Posts: 271 Joined: Oct 2015 Thanks guys. I'll try your suggestions and let you know what I find. 37RAGTOPMAN 02-19-2024 @ 4:23 PM reply profile send p.m. Senior Posts: 1961 Joined: Oct 2009 Did you try running the car without a air cleaner and see if it runs different, it might be clogged ? or partly clogged you could also put a paper towel under the 2 large head SCREWS , in the float bowl , take them out and see what comes out, you could also take a spray carb cleaner and spray it in the screw holes in the bowl and see you might have water in the fuel system, take a fuel sample, use a glass jar, so you can see what the fuel looks like when you have it running, does the exhaust seem flowing ok, any noise ? hope this helps, 37Ragtopman,,Maine Drbrown 02-20-2024 @ 10:32 AM reply profile send p.m. Senior Posts: 570 Joined: Nov 2013 All above are certainly good suggestions. Please keep us posted as symptoms in your case seem unusual to hear. Additional thoughts: (1) Do you use stock set-up re fuel pump/supply or do you also have an electric auxiliary pump ? (2) I understand engine idles/accelerates adequately except under conditions you state, which suggests to me, excepting a defective coil, ignition system is not impaired and there's an apparent loss of fuel flow/supply ... wouldn't hurt to try another coil; (3) I believe one may remove the top of carbonator and inspect the bowl for contaminants - good time to check the float cut-off setting/level ; (4) Check your fuel pump output pressure - a weak pump may not deliver enough gas - and likewise check idle screw settings. (5) The flex connection hose at the fuel pump, assuming you have one, may have internal deterioration that restricts gas flow. (6) Regarding gasoline, if you are driving once or twice a month I doubt that's an issue. Good to keep tank full during the cold season and use a preservative in gas to avoid moisture contamination. My '47 may sit 3 or 4 months with out running but with priming by electric aux pump for starting, will start and run without problem. This message was edited by Drbrown on 2-20-24 @ 10:35 AM 46coupe 02-20-2024 @ 1:29 PM reply profile send p.m. Member Posts: 271 Joined: Oct 2015 Thanks for all the suggestions. I hope to have time tomorrow to do some troubleshooting. I know the tank is full. I am using 4oz of MM in the gas tank. I have the original fuel setup, no electric pump. When I first start the car after it sits for a couple of weeks, it runs very rough and dies if I don't keep it at about 1200-1500 rpms. After running a few minutes it smooths out. I wondered if I have a sticking valve . The coil is new. The old one would fail to restart the car when it was hot. I kept it and might try it if the problem continues. Before that I will try the carb cleaner and check the float level and fuel volume. The tank is vented, so much so that I have to seal the cap to keep the gas from evaporating. I'll get back to you all to let you know what I've found. 46coupe 02-21-2024 @ 2:03 PM reply profile send p.m. Member Posts: 271 Joined: Oct 2015 I finally got some time to run some experiments. Checked the gas cap and it's ok. I had taken the air cleaner off and sprayed carb cleaner in it. On start up the engine ran rough but after about 5 minutes it cleared up and kept running without skipping or slowing down. T he the carb cleaner was used then. Well I took it on a test drive of 15 miles and it ran great. I had to stop for lights and general traffic and had no problem. I hope this has fixed the problem. However, I' m going to keep checking the other things you all mentioned. One thing that I was going to ask, and my question was answered when someone suggested removing the air cleaner. I have the stock air cleaner but the guts of it have been removed and a regular paper air filter was installed. I have searched several places to find a replacement using the dimensions of the air filter but have not been successful. Not wanting to introduce dirt and debris into the carb, I turned the filter upside down to expose the new part of it to the air. Could this be what has caused the problem? Would anyone know what air filter might fit? I am trying hard not to have to use one of those tiny chrome things. Does anyone sell the inside "cartridge" for an oil bath air cleaner? carcrazy 02-21-2024 @ 4:47 PM reply profile send p.m. Senior Posts: 1659 Joined: Oct 2009 Measure the dimensions of your paper air filter and search the air filter elements available from Speedway Motors. Their website is speedwaymotors.com. If they don't have the size you require, you can bring your old air filter to a local NAPA or other auto parts store to see if they either have one in stock or can order the proper size filter for you. carcrazy 02-21-2024 @ 9:45 PM reply profile send p.m. Senior Posts: 1659 Joined: Oct 2009 I agree with you, I don't want to run one of those tiny chrome things on my Flathead Ford. If you have room for a 10" diameter air cleaner, you can run an air cleaner from Speedway. It is P.N. 240-1195 and uses a 10" dia. X 2" tall air filter (P.N. 91011098). To use this air cleaner on your Ford/Holley 2V carburetor, you will also have to purchase a 4" dia. air cleaner, P.N. 91011005 for parts. The parts to use from this 4" dia. unit are the mounting bracket that accepts the mounting stud and wingnut and the hose clamp to mount the bracket to your carburetor airhorn.

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