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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: aleighs1990 on June 16, 2016, 09:35:49 pm
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Occasionally when driving my 76 c10, if I try to push the throttle all the way or climb a steep grade, or even open it up enough to climb a hill going down the highway, the engine will try to cut out on me, and I have to stay off the throttle for a few seconds before I can push the pedal again, almost like it's trying to flood mid-acceleration. It also seems like this happens more if it is hotter outside, but that could just be coincidence. This seems a bit unsafe on busy highways where everyone thinks they are in a race. A few people who know more than me about carbs altogether (as in grew up with them) seem to think there is too much fuel flowing thru the carb when i open it up (or add the extra work load of pulling a grade). Are these people right, and how do I correct the issue?
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Sounds more like too lean. Engines will burn very rich mixtures, but get too lean, and the fire goes out.
Could be a bad accelerator pump. When you open the throttle, the air rushes in and it takes the gas flow a bit to catch up. To fix this, there is a piston in a little cylinder full of gasoline in the carb. When you push on the throttle, it squirts a metered amount of raw gas into the carb throat to make up the difference.
That is, it will if the o-ring on the piston isn't worn out, and isn't so old as to have hardened.
To check, take off the air cleaner, and, with the engine not running, look down into the carb while you manually twist the throttle linkage open. You should see gas squirt into the throat of the carb. No squirt, you have a problem. Replace the piston in the accelerator pump. They're cheap, and easy to replace.
If the accelerator pump is broken or not working properly, you will get a bog or the engine will die when you open the throttle too quickly. Nurse it open slowly and it will work OK.
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To add to that when your looking in the carb while manually pumping you should have to even amounts of gas squirting in each barrell. If not you could have picked up trash in your jets. EBay has rebuild kits like 20 bucks. Comes with new accelerator pump.
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I forgot to add that at times it backfires into the carb immediately before bogging down. this is the same thing it does in the winter when it's real cold outside and i try to drive it without it warming up. granted there is no choke on it. still sound like the same issue?
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Timing been checked?
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Not in the time I've owned it
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i would start with making sure your vacuum hoses are in good shape and check for vacuum leaks. then on to the timing. its simple and cheap or free if you have a timing gun, verify the vacuum advance is working then hook the vacuum advance up to manifold vacuum.
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Like Rich said, check accelerator pump discharge, check fuel hoses for kinking
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Little history also, mileage, recent work, just started happening, how frequent, only under heavy throttle?