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Topic: idle after heating up

in Forum: C3 Engines


idle after heating up

Posted: 11/9/06 11:15am Message 1 of 10
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finally been able to drive the car a bit further than just up and down the road but i noticed now that after the engine really has heated up while driving ( not just 5-10 minutes ) and then have to stop for traffic lights etc..  the engine has problems running idle .. slower and slower till it stops... but it starts up right away again. .........   i was thinking maybe the fuelline get warmed up too much making the fuel to warm when it enters the carburator???. does this make sense..or should i think about other reasons?

With a short ride the engine runs perfectly idle..

art-corvete



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idle after heating up

Posted: 11/9/06 12:04pm Message 2 of 10
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Frederick, MD - USA
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Vette(s): 1969 convertible L71 427/435 4-speed black interior
Could be a carburetor problem. Sounds like after the engine heats up and the choke cuts off the problem begins.    It may need a thorough cleaning or rebuilding.

Did you install a different camshaft? If the cam has different specs, the carb may no longer be jetted to match. I had that problem in my '78. A previous owner installed a different cam and the engine simply wouldn't idle...the jets were now too small for the idle circuit. New jets cured the problem.

Another possibility is if your car has an idle solenoid or a/c kick-up solenoid. If it's out of adjustment or gone bad you can have the same problem.


idle after heating up

Posted: 11/9/06 12:12pm Message 3 of 10
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i haven't connected the choke(cable) .. it is a manual choke.
camshaft is still the same (edelbrock performance) and a holly carb...
 
but if it would be one of the above reasons i would  expect the problem to start sooner ... in 5 or 10 minutes.... but my problem takes longer to start acting up.
 
art-corvette
 
 



idle after heating up

Posted: 11/9/06 7:37pm Message 4 of 10
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Duncanville, TX - USA
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Sure sounds like a fuel problem. I'd agree with Bruce on the carb as the source.
 
 When it starts back up, do you notice any black smoke from the tailpipes?
 
Does it just start idling down slowly until it dies, or does it start running rough, and then die?
 
When it starts back up, will it idle ok then, or does it die again within seconds?



Joel Adams
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idle after heating up

Posted: 11/10/06 10:00am Message 5 of 10
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think i got closer to the solution and the source probably the carb indeed.

today i took off the airfilter and first thing i noticed was a fuel leak on the intake needle  (A) ( not that that caused my prob)



then i checked the fuel level check plug (B) and the fuel was pouring out  so i have adjusted the intake needle till the fuel was not pouring out anymore.

the result was that after a cold start the engine wasn't running that smooth  on idle as before ( still haven't attached the (manual)choke cable so it seems with a cold start i need the choke in future)  anyway .. after driving some time i still have the same problem as before.. . engine running too slow on idle  and stops (when putting a little pressure on the gas pedal the car keeps running ok..so i guess now i best adjust the idle adjustment needle(s) (C) ??
uhh.. guess i need to turn the needle(s) outwards ?
ohh. and the smoke that comes out of the tailpipes is not black...the car smokes a bit more (oil) blue smoke then before i took the car apart.. but i guess that is caused by not running for more than a year .. anyway i'll give it some time to see if the blue smoke gets less

last time i have adjusted a simple  carb was of a motorbike.. 25 years ago.. so no experience with the bigger carbs.


art-corvette







idle after heating up

Posted: 11/10/06 4:08pm Message 6 of 10
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Red Lion, PA - USA
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Art
from what I remember on my old race cars the (A) needle is only to set the height of the float level in the bowl. The (B) plug should have gas come right up to the lower edge but not run out with engine running. Once this is set forget them and you may need to adjust other settings on the carb.





idle after heating up

Posted: 11/10/06 7:48pm Message 7 of 10
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Rod is correct. The fuel level should be adjusted at the "A", so it just barely trickles out of sight plug "B". The idle mixture screws "C" are for fine tuning the idle mixture, best done with a vaccuum gauge connected to the intake fitting, and adjusted for the highest vac. reading possible.


Joel Adams
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idle after heating up

Posted: 11/11/06 7:28am Message 8 of 10
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think i have been able to solve the prob , fuel level in plug B is ok, furthermore i have adjusted the ..i think it is called the high idle adjustment screw..on the other side of the carb  . atleast the car doesn't stop running anymore.

but furthermore i got a bit confused about the carb... i thought i had a double pumper  but someone told me looks might be deceisive.:




the carb has 2 fuellines connected, fuel is also in that chamber (B)on the rear end , with a a functional needle (A) on the rear too ...only i don't see any fuel squirt out in the carb on the rear as i see on the front ( below the  choke valve ..or is that rear end only for when the extra power is needed??


art-corvette





idle after heating up

Posted: 11/11/06 5:04pm Message 9 of 10
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What you have is a dual feed, vaccuum secondary carb(not a "double-pumper"). The secondaries are opened by vaccuum, as needed. There is no extra fuel "squirted" into the secondary barrels when you pump the gas. The secondaries are fed fuel by a vaccuum signal internal to the carb.


Joel Adams
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idle after heating up

Posted: 11/11/06 8:08pm Message 10 of 10
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thanks for the lesson :)
 
art-corvette



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