Hard starting after warmed up - JeepForum.com
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post #1 of 20 Old 06-10-2021, 10:49 PM Thread Starter
Renegade82
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Hard starting after warmed up

So I have an issue with my engine that I didn't seem to have a few months ago. My engine is a 258 with maybe 3k miles since it was professionally rebuilt 2 years ago. It's running a Weber 38 and a DUI hei dizzy, but otherwise stock, sans the .30 over during rebuild.

The issue is its hard starting after it's warmed up. When cold it starts normal, slowly ramps to high idle, and then idles fine when you kick it down. But when I drive it somewhere and then shut it off, it struggles to start again, both when the peddle isn't touched or you just bump it slightly. If I depress it while turning it over it will start, but with some rumbling till it flattens out with some light pedal.

It runs fine, it just has starting issues once warm/hot. I'm not sure what might cause it but I'm thinking a carb issue of some sort. Maybe a choke issue since I removed my icm when I installed my hei. Not sure how the choke circuit gets energized. But that was also a year ago too. Any thoughts.

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post #2 of 20 Old 06-10-2021, 11:50 PM
Chiss
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Advance Timing a little
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post #3 of 20 Old 06-11-2021, 12:26 AM
mudbfun
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If it is a choke issue then it may just need an adjustment. Warm it up then pull the air breather and check the choke position. It should be completely open when warm.
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post #4 of 20 Old 06-11-2021, 01:03 AM
Delta0
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What colour smoke do you get out the tail pipe when it first starts?
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post #5 of 20 Old 06-11-2021, 06:44 AM
Matt1981CJ7
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My guess is the choke isn't working or needs adjustment, as Mudbfun said.

It's an easy check.

Matt
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post #6 of 20 Old 06-11-2021, 03:16 PM
pedal2themetai
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Hi, does it turn over good and just not start or does it turn over sluggish .. Check the voltage at the coil.. should be 9v runnig but 12v at (during) start up..
good luck
tim
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post #7 of 20 Old 06-11-2021, 03:59 PM
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I’m thinking a GROUND issue as well. A poor ground at starter will give you symptoms like that from over heating. Remove, clean ALL of your grounds well and retighten with dielectric grease.
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post #8 of 20 Old 06-12-2021, 08:27 AM Thread Starter
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No, it turns over fine, it's an initial lack of combustion thing. This Jeeps got grounds upon grounds and then some. And the hei is wired using a relay so it's got full 12v all the time.
Hopefully I get a chance this weekend to look at the choke and check the timing. Seems to me it was at 10deg and I know Webers like it about 12deg. What voltage should be at the choke wire, is it a full 12 volts, does anyone know?

Delta0 - Do you mean at a cold start or when warm and it finally starts up?

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post #9 of 20 Old 06-12-2021, 09:38 AM
87MJTim
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Vapor lock. Fuel in the supply line vaporizes.
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post #10 of 20 Old 06-13-2021, 07:57 AM
Matt1981CJ7
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Choke should have full battery voltage when the engine is running.

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post #11 of 20 Old 06-13-2021, 07:17 PM
BagusJeep
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I would have said vapour lock as a possibility as well but your very neat engine bay has it correctly plumbed.

Is the filter correctly oriented? it is just out of sight in the pic.
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post #12 of 20 Old 06-14-2021, 11:38 PM
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Quote:
Originally Posted by Renegade82 View Post
No, it turns over fine, it's an initial lack of combustion thing. This Jeeps got grounds upon grounds and then some. And the hei is wired using a relay so it's got full 12v all the time.
Hopefully I get a chance this weekend to look at the choke and check the timing. Seems to me it was at 10deg and I know Webers like it about 12deg. What voltage should be at the choke wire, is it a full 12 volts, does anyone know?

Delta0 - Do you mean at a cold start or when warm and it finally starts up?
I take it that with your engine bay you still have the factory return line hooked up to the filter. If it is you are not getting vapor lock. Your carb is getting too hot and boiling the fuel which then runs into the intake. I am sorry I cant tell you a fix because I am still trying to find a fix for my jeep in the summer time. If you slowly push the throttle to 50% and it starts up way faster then I am right of the fuel boiling out and through the venturis.
If you find a fix let us know. My poor 25 year old starter is having the time of its life.
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post #13 of 20 Old 06-15-2021, 09:04 AM Thread Starter
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Bagus - Yes the filter has the return outlet at high noon.

ctorj - I was told to try just tapping the pedal before starting but that doesn't seem to help. I haven't tried giving it a good shot with half pedal but I will try it next time. But it doesn't seem to be a "summer time" only issue. It started in late winter.

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post #14 of 20 Old 06-15-2021, 09:05 AM Thread Starter
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Double post. Doesn't let you delete posts anymore.

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post #15 of 20 Old 06-15-2021, 05:42 PM
hp_lovecraft
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Looking at the picture, the fuel line is right next to the exhaust? When mine was similar, it was murder trying to start when hot. Either vapor locked or boil off. I think the later since when I looked into the throttle body, the intake was full of gas. The liquid flashing to gas made enough pressure to force fuel past the bowl, flooding the carb, and spilling into the intake.

So I rerouted the fuel line over the valve cover.... problem disappeared. It also fixed the problem that it was hard to start when it had been sitting more then a day.

Could also be a stuck choke. Mine would do that for a while. Choke would get stuck on, and foul the plugs while driving... and not want to start hot. I'd have to clean the plugs in the parking lot.
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