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1973 - 1979 F-100 & Larger F-Series Trucks Discuss the Dentsides Ford Truck

Carb choke question

 
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Old 02-09-2019, 02:06 PM
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Carb choke question

Hello guys. Here is what I have. 1973 F100 360 V8. 2 bbl carb. Pretty standard stuff. Temps here in Tennessee have been averaging 20s or so in the morning. I turn the key give it one stab and the engine starts on the first crank with good solid idle. After a minute or so I stab it again and the idle falls to about half and I can back it right out of the garage no issues. No fits or misses. Upon driving it away the engine wants to drop out or hesitate and I need to "goose" it a time or two to keep it running until it catches and then accelerates pretty normal. After it warms up there is little to no


hesitation at all. What could cause the engine to want to stall at very low speed and that from a stop upon acceleration? I think I have the choke set properly but can't seem to find why it wants to die on me. Any suggestions would be helpful. The photos show the choke re-set so I could try driving it at this "new" setting to see if it makes a difference. This is where the butterfly is after about three hours of sitting. It is now about 42 degrees outside. Thanks. DO'
 
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Old 02-09-2019, 02:20 PM
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Check fuel height in carb bowl on level ground. Can experiment with accelerator pump rod settings. These are set in different positions depending on outside temperature. The uppermost hole is for temps below 40F, if it's not there now can try that. 2nd from top is 40F to 90F temps, most driving.

Also on the forward end of pump rod, try the inboard slot position, that should be a richer overall setting. Look for a puff of black smoke at the hesitation point, too rich a mixture can cause hesitation too. Unlikely in this weather, but who knows.

With engine OFF goose throttle through full travel and look down carb throat for two streams of fuel from the pump.
 
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Old 02-09-2019, 02:36 PM
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Tedster9, thanks for the reply! Will take a look while I still have light. I have noticed that I haven't had these issues until we started getting very low temps as of late. Ok all you guys from the upper mid-west...I know these temps are nothing for you. :-)
 
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Old 02-09-2019, 03:45 PM
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Bogging down, hesitating, stumbling from a dead stop or when accelerating at speed is indicative of a worn accelerator pump and check valve.

This is a common problem with the Auto-Lite/Motorcraft 2100 series 2V that was used from 1963 thru 1974 on just about everything.

When the 2150 series carb was introduced in 1975, the check valve was the same, but the accelerator pump was much larger, so the problem basically went away.
 
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Old 02-09-2019, 04:59 PM
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Bill, thank you for the reply. That is probably what I will look at next. I assume I can get what you mentioned in a carb rebuild kit? I performed the tests that Tedster9 suggested with no change so now I must move on to what you suggest. We are expecting rain for the next couple of days so I may have to wait til it clears so I can back the truck out of the garage. Thanks again! DO'
 
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Old 02-09-2019, 05:08 PM
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Originally Posted by moveoverGM View Post
Bill, thank you for the reply. That is probably what I will look at next. I assume I can get what you mentioned in a carb rebuild kit? I performed the tests that Tedster9 suggested with no change so now I must move on to what you suggest. We are expecting rain for the next couple of days so I may have to wait til it clears so I can back the truck out of the garage. Thanks again! DO'
There's only one carb kit for the 2100 2V, includes the accelerator pump, check valve, needle & seat, power valve and the gaskets.

D4AZ-9A586-A (Motorcraft CT-499-D) / Available from Ford & auto parts stores.

 
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Old 02-09-2019, 06:38 PM
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Originally Posted by moveoverGM View Post
Bill, thank you for the reply. That is probably what I will look at next. I assume I can get what you mentioned in a carb rebuild kit? I performed the tests that Tedster9 suggested with no change so now I must move on to what you suggest. We are expecting rain for the next couple of days so I may have to wait til it clears so I can back the truck out of the garage. Thanks again! DO'
You can get the accelerator pump diapram at Napa. I had one leaking and just bout one a few weeks ago. If a rebuild doesnít help it you can find a new not reman 2150 clone for under $100 on Amazon. Great luck from a seller called morphon
 
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Old 02-09-2019, 07:50 PM
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Originally Posted by moveoverGM View Post
Ok all you guys from the upper mid-west...I know these temps are nothing for you.
42 !!? Good sleepin' weather, that's what that is. Git yer *** out there and fix the carb! lol
 
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Old 02-09-2019, 08:12 PM
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Talking

Originally Posted by Tedster9 View Post


42 !!? Good sleepin' weather, that's what that is. Git yer *** out there and fix the carb! lol
Really Funny!! I don't mind so much the cold but rain water runnin' down my butt crack is a bit too much!
 
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Old 02-11-2019, 03:57 PM
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Update: Did everything mentioned above by my friends here. Even bought a rebuild kit and replaced the check valve and accelerator pump. Had to take the top off the carb to get at a small piece of check valve that fell inside the bowl and looked very clean in there. Replaced the small fuel filter at the carb. No change. Did however do the Ol' spray carb cleaner test. Noticed that when the carb is relatively cold the engine surges when I spray a little cleaner at the throttle shaft and bore on drivers side. It goes away though for the most part when the engine and carb come up to temperature. Maybe the temp is causing the space between the shaft and bore to seal up a little thus minimizing the vacuum leak? Any thoughts? DO'
 
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Old 02-11-2019, 06:03 PM
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Maybe adjust the electric choke coil a notch or two richer and see if that helps, then set it back to where it was when the morning temps come back up.
 
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Old 02-11-2019, 09:16 PM
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There was a guy on this forum discussing the center shaft butterfly area and how it cannot be rebuilt. His had been rebuilt using your parts store kit and he was frustrated, I think he found the butterfly shaft was the culprit for poor performance?

I do not know how to dial in older threads but it is somewhere on here posted within the last month.
 
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Old 02-11-2019, 09:50 PM
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The carb has been rebuilt based on the tag in the pic, professional outfits will re-bush the throttle shaft mount holes if they are wallered out. I don't think this is the problem. Maybe. Could try stuffing chassis grease in there, and see if the problem goes away.

It may simply be the truck isn't warming up fast enough and/or the choke is coming off too early? My old beast has a manual choke so I've never had much experience with electric chokes. I once had a C20 w/ a Quadrajet now that I think about it.

The only way I've ever been able to eliminate stubborn or strange stuff is go through line by line on the troubleshooting. For example, is the thermostat in good shape, is it the right temperature rating. Does the heater work good? I use a 195į T-stat, it's important regardless that any engine warm up as quickly as practicable even in the summer. A defective thermostat can make engine run cold, by sticking open. This is better than stuck closed, but it still presents a problem.

Check your spark plugs, they are kind of a window to the inside of the engine and how it's running. What do they look like? Are they black as coal, dripping with fuel, etc, or running lean?
 

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