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68 GMC dies when I give it gas


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Gabriel_Mark
New User

Jan 26, 2015, 3:52 PM

Post #1 of 2 (529 views)
68 GMC dies when I give it gas Sign In

I have been fixing up a 1968 GMC truck. I have gotten the truck to start up and idle pretty good. However, when I give it a little gas, the car wants to die, or does die. I have to feather the throttle and keep the rpms real high to drive it. The accelerator is definitely hesitating. The carb is coughing. And I have been trying to locate a vacuum leak which is normally fairly easy. I believe this is the problem. But all the main hoses seem fine and the leak sounds like it is coming from somewhere behind the carb near the distributor.

I understand this was all over the place. But Im looking for any advice on leaks that are hard to find. Or reasons why the accelerator hesitates and wants to stall the car.

Thanks!


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jan 26, 2015, 5:28 PM

Post #2 of 2 (515 views)
Re: 68 GMC dies when I give it gas Sign In

Out of all that I can only guess this is a Chevy V8 just because you said distributor was behind carb. So now tell us what carb at least either a Quadrajet (4 barrel) or a Dualjet (2 barrel) or something else put on it by now?


Rochester carbs were both perfect when perfect and took lots of adjusting to get just right new. It's not new so the guess is the accelerator pump is lousy or about gone.


Common issue for many and these too. Would about stall upon acceleration lacking a squirt of extra fuel to change engine speed.
The hard part now is finding anyone still alive who knows how to put just that part in without wrecking all adjustments.


Carb issues that are common if that:


* Choke pull offs - most common to me.
* At the age and tons younger vacuum leak at base gasket but wrong symptoms stated for that.
* People deleted automatic chokes for hand manual ones and screwed the whole carb up - real common!
____________________________
Of current and more lately if just new and older out of a box the gaskets and rubber parts will NOT tolerate the ethanol in the gas sold today so it must be changed to new or find fuel sold without AFTER the fix.


What carb do you have - I actually should remember most details if OE. If you can try finding the # on the side of it and post that and I'll try to find exact specs. Should be on mid body of carb, an 8 digit # probably begins with 17******. Hard to see it if not cleaned off,


T







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