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Chevy K10 250 CID vacuum problem...

M

MBU

Member
I have a K10 250 CID Chevy truck that seems to have a vacuum problem. When the engine decelerates quickly (let off the pedal) the vacuum goes to zero and the engine dies. Does anyone have any suggestion as to what could cause this?

I have removed different vacuum lines one at a time but that hasn't revealed any leaks.

Thanks for your help!
 
does the truck have a egr valve??? sounds like it may be hanging open long enuff to kill engine...some you can clean...some gotta be replaced...i use gumout carb cleaner to clean mine...gets carbon out.
 
BCnT,

Thanks for the reply!

Yes it has an EGR valve. When the engine first starts (cold) one can see the vacuum pull it in and as the engine gets warm it is released.

While I'm at it....Where is a good place to check the vacuum?
 
Sounds like the dashpot is missing or not working. What is a dashpot? It is a diaphragm with a calibrated leak to stop the throttle from slamming shut for about the last 1/4" of travel to curb idle position.
 
don't worry about vacuum. What year is your truck ? EGR valve should not move untill part throttle . Sure you are not looking at a choke pull off ? Hold your hand over the carb and choke it some .If it runs better you are lean .Either carb problem or vac leak . You can spray carb cleaner around intake and carb if smoothes out theres your leak .
 
(quoted from post at 19:20:05 02/10/10) Sounds like the dashpot is missing or not working. What is a dashpot? It is a diaphragm with a calibrated leak to stop the throttle from slamming shut for about the last 1/4" of travel to curb idle position.
Click to expand...

Brian,

That's an interesting point. Is there a dashpot on this carburetor?


81-Chev-K10-carb.jpg





(quoted from post at 20:39:45 02/10/10) don't worry about vacuum. What year is your truck ? EGR valve should not move until part throttle . Sure you are not looking at a choke pull off ? Hold your hand over the carb and choke it some .If it runs better you are lean .Either carb problem or vac leak . You can spray carb cleaner around intake and carb if smooths out there's your leak .
Click to expand...

The year for the truck is 1981.


Thanks Brian and Bryan for you help! I really appreciated it!
 
That is a Varajet carb . It has a primary and a secondary choke pull off ,the two vac deals on front and back of carb . The Solenoid on the bottom is idle control . Usualy when a/c is on ,it is energized . The EGR valve will be on the intake manifold . You can unplug the line off it ,if you problem quits . Call me in the morning if you are still having trouble . I can maybe help you figure it out .319-329-0915
 
(quoted from post at 22:32:05 02/10/10) That is a Varajet carb . It has a primary and a secondary choke pull off ,the two vac deals on front and back of carb . The Solenoid on the bottom is idle control . Usually when a/c is on ,it is energized . The EGR valve will be on the intake manifold . You can unplug the line off it ,if you problem quits . Call me in the morning if you are still having trouble . I can maybe help you figure it out .319-329-0915
Click to expand...


Bryan,

Thank you very much for the offer!

I'm going to test a little more an see what happens. If I can't get anything to work I'll give you a call.
 
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