Carburetor Problems
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Cross-Country
Joined: Apr 2019
Posts: 68
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From: Walla Walla
Carburetor Problems
Hello!! I recently bought a 1970 F250 with the 390FE and have finally gotten it running. The issue I am experiencing is that the truck will die at low RPM, especially when it is colder like when I first start it. I used a bunch of carb cleaner because I thought it might just be gunky, but that has not seemed to solve it. I don't have any experience with carburetors, so any advice would be great.
Lead Driver
Joined: Jul 2011
Posts: 8,678
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From: On the Edge of the Desert
Carburetors aren't like fuel injection. They don't run themselves. You have to help them when it's cold out.
Sounds like you need to get the choke working, and possibly make some adjustments to the idle mixture and speed.
Sounds like you need to get the choke working, and possibly make some adjustments to the idle mixture and speed.
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Cross-Country
Joined: Apr 2019
Posts: 68
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From: Walla Walla
I believe it has the electronic choke, as there is no manual option in the cab. Typically I give it a couple pumps of the gas and then turn it over while giving it a bit more. I haven't usually had a problem with it starting so much as it staying running without my keeping the RPMs up.
Post Fiend
Joined: Apr 2002
Posts: 19,311
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From: Waterloo, Iowa
Welcome to FTE Brandon
You're in for a great ride in your "new" Ford truck .. But since it is only new to you it needs a good thorough inventory sort of inspection (and we need pics!!) and almost certainly, a good, thorough Tune-Up.
One important characteristic of carburetors is pretty much any other engine defect or mistune somewhere else in the engine will make it seem just like that it's the carburetor at fault when it really isn't, the old joke with mechanics went "90% of carburetor problems are ignition related." Carburetor cleaner has its uses sometimes, but save it for when you do a full carburetor rebuild.
You're in for a great ride in your "new" Ford truck .. But since it is only new to you it needs a good thorough inventory sort of inspection (and we need pics!!) and almost certainly, a good, thorough Tune-Up.
One important characteristic of carburetors is pretty much any other engine defect or mistune somewhere else in the engine will make it seem just like that it's the carburetor at fault when it really isn't, the old joke with mechanics went "90% of carburetor problems are ignition related." Carburetor cleaner has its uses sometimes, but save it for when you do a full carburetor rebuild.
Mountain Pass
Joined: Oct 2020
Posts: 214
Likes: 8
Are there any changes to it's ability to stay running once its nice and warm, or does this happen regardless of the engine temperature - hot or cold?
Just thinking out loud...
Just thinking out loud...
- Only when cold - then choke or maybe a fuel supply/atomization issue. (Have you changed the fuel filter and how does the float bowl look - debris-free?)
- Hot or cold - could be a sticking/malfunctioning choke that is flooding the engine (how do your plugs look? Any rich/unburned fuel smell?)
- Hot or cold - could be just an idle speed issue and or mixture adjustment issue with a little bit of timing sprinkled in for good measure. (As Tedster suggested - have you done a full tuneup with points, condenser, etc? Might do it wonders...).
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Cross-Country
Joined: Apr 2019
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From: Walla Walla
So from what I can tell, it runs much better when it is warm, but I typically do not have any issues firing it up, which seems to me would definitely point towards the choke. As long as I keep the revs up it is just fine when it's cold, but if I let off the gas is when it dies. I did a sort of tune-up with it when I purchased the truck (plugs, wires, cap, rotor), so I believe those shouldn't be the source of the problem.
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Post Fiend
Joined: Apr 2002
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From: Waterloo, Iowa
How did the old spark plugs look? That is an important thing, keep an eye on how they are burning because they don't lie. You can tell your tune is getting better and closer to ideal as they improve in appearance. Modern gasoline will result in very clean burning spark plugs, even in old school engines, when they are running well.
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Cross-Country
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From: Walla Walla
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