Any suggestions?
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New User
Joined: Mar 2018
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Any suggestions?
So I recently purchased a 1978 F-250 with a 400. Motor runs great other then when first starting while it's cold. It'll start right up but will not idle on its own until she warms up a bit. The problem I'm having is after I take it on a hwy and have it at speed for awhile take it home and park it- next morning it's a VERY difficult start up. (almost to the point of draining the battery all the way down) while driving it around town no problems whatsoever on cold or warm startups. Been on hwy twice with it and had this problem twice now after it sat overnight.
Has a remanufactured 2 bbl carb installed recently by previous owner (who runs a auto repair), also new tank sending units. Any suggestions out there as to what I should be focusing on? Thanks -Mike
Has a remanufactured 2 bbl carb installed recently by previous owner (who runs a auto repair), also new tank sending units. Any suggestions out there as to what I should be focusing on? Thanks -Mike
Cargo Master
Joined: Nov 2007
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Look for leaks to see if the fuel system is draining down while sitting. Otherwise I'd say it's a tuning issue. Check base timing first then adjust the carb. I'd look at the choke adjustment first if it runs fine once it's warmed up. If you pump it once or twice, then start it, does it go to a higher idle?
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I pump it 3 times and start it. If I slowly let go of the gas pedal after it starts (not warm) it will idle very low and stall. Once it's warm I can start it and not hold gas pedal to stay running. It'll start and idle fine
Grumpy goat
Joined: May 2017
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I'd suspect the choke isn't functioning properly. Also sounds like the carb is a little lean.
Cold air is denser than hot air. So when a cold engine first starts up, the choke (assuming you have electric choke) should restrict air flow, and increase idle RPM until the engine heats up. As the engine heats up it also heats the air as it passes through the intake manifold. Ideally, the carburetor is tuned to have best air fuel ratio once it's warmed up. The choke takes care of air fuel ratio until engine is at normal operating temp. Modern car EFI does the exact same thing, except the transitions are more fluid and barely noticeable.
Cold air is denser than hot air. So when a cold engine first starts up, the choke (assuming you have electric choke) should restrict air flow, and increase idle RPM until the engine heats up. As the engine heats up it also heats the air as it passes through the intake manifold. Ideally, the carburetor is tuned to have best air fuel ratio once it's warmed up. The choke takes care of air fuel ratio until engine is at normal operating temp. Modern car EFI does the exact same thing, except the transitions are more fluid and barely noticeable.
Logistics Pro
Joined: Jul 2005
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Yep, make sure your choke is closing. Your choke might be adjusted for winter, and not closing enough in the warm weather.
So once you adjust it to close in the warm weather it should be fine, but come autumn, the choke might not open quickly enough on that first really cold morning,
So once you adjust it to close in the warm weather it should be fine, but come autumn, the choke might not open quickly enough on that first really cold morning,
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Ok you guys are awesome, went out and checked choke- the dial was loose and rotated back so it wouldn't close butterfly. Adjusted and truck starts now at high idle and butterfly opens up as truck heats up. Would this explain hard start after a highway drive though? Or should I be looking for something else now?
Grumpy goat
Joined: May 2017
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Woo Hoo, you fixed it!
Yes, it could be a cause for hard starts. And yes, always look for other problems. Btw, I really hate electric chokes. Manual chokes put you in charge of how to start the truck, and they don't get out of adjustment.
Yes, it could be a cause for hard starts. And yes, always look for other problems. Btw, I really hate electric chokes. Manual chokes put you in charge of how to start the truck, and they don't get out of adjustment.
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Thanks Mike!
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