QuestionQUESTION: Hi Tom
This is for my dads truck. He has a 1981 chevy C10, with a 250 engine. The motor has a little over 80,000 miles on it. He put a remaned rochester 2 bbl carb on it. It has never ran up to par, and we are at a loss of why. heres the issue: It idles pretty good, occasional bump. If it is revved up slowly its sounds good, BUT, when we push the throttle down fast, or semi fast, it bogs and almost wants to stall until it seems to catch up and rev back up. We are not sure what the issue it... also small tick, but not bad...
Heres what we have done:
- new plugs, cap rotor, wires
- timing is set
- new fuel filter
- we unplugged the fuel line and it seems to send a good amount of fuel.
- checked compression, each cylinder is between 145-150.
It bogs, and between shift is backfires, we cant figure it out, any ideas?
Thanks
Kolby
ANSWER: HI KOLBY,OK FIRST THINGS FIRST,WHAT YOU ARE TRYING TO SAY I THINK IS THAT THE ENGINE HESITATES IF YOU ACCLERATE AT A NORMAL RATE. THIS IS USUALLY A BAD OR IN YOU CASE A FAULTY ACCLERATOR PUMP IN THE REBUILT CARBURETOR. DID THIS START ACTING UP WHEN YOU REPLACED THE CARB ??? THESE REBUILD CARBS TODAY ARE SO-SO. I AM BEING NICE. LET ME GUESS A CARBONE REBUILD ?? I WOULD LIKE YOU TO GET A FLASH LIGHT AND LOOK DOWN THE TOP OF THE CARBURETOR AND OPEN THE THROTTLE AT A SLOW RATE,YOU SHOULD SEE A [STEADY] FLOW OF FUEL SPRAY OUT OF THE AIR HORN DOWN TO THE THROTTLE PLATE. BOTH SIDES OF CARB. NOW THAT YOU SEE WHERE IT IS SPRAYING FROM OPEN IT UP RATHER FAST,IF THERE IS A SPRAY AND THEN IT STOPS OR SLOWS DOWN AND PICKS BACK UP AGAIN THERE IS A PROBLEM WITH THE ACCL PUMP,KEY WORD IS [EVEN] SPARY FAST OR SLOW..I THINK YOU WILL FIND UPON FAST THROTTLE THERE WONT BE ANY FUEL.THIS WILL CAUSE HESITATION. THERE COULD BE OTHER PROBLEMS WITH THIS BUT LETS RULE THIS OUT FIRST..THE TICKING NOISE IS JUST A LAZY LIFTER OR OUT OF ADJUSTMENT ROCKER ARM. THIS WILL NOT CAUSE YOUR PROBLEM..THE OCCASIONAL BUMP AS YOU SAY COULD BE CAUSED BY THIS LAZY LIFTER, OR VALVES OUT OF ADJUSTMENT OR A STICKY VALVE AND LASTLY A OUT OF ADJUSTMENT CARBURETOR ,AIR FUEL/MIXTURE..GET BACK TO ME AFTER YOU DO YOUR HOMEWORK WITH MORE UPDATES. I HOPE THIS HELPS YOU. WHEN YOU LEAVE THIS SITE WOULD YOU PLEASE RATE MY ANSWER. THIS WILL HELP ME..THANK YOU ,TOM.
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QUESTION: Hi Tom
Thanks for the reply, I did go out and shine a light down the carb, but couldnt see the spraying. I did however go and buy a rebuild kit for the Carb. I just put it on and it does seem to run better. And I think it does accelerate better. My question is, is it normal to bog a little if you just slam the peddle down fast and in a way "surprise" it. Because it still does that.
Oh and you were correct about the accelerator pump, when i removed it it was bent, i straightened it out and put it back in.
thanks.
kolby
AnswerHI KOLBY,SO THE PUMP SHAFT WAS BENT,THIS WOULD EXPLAIN THE BOG,IT WAS NOT GETTING THE FULL SHOT OF FUEL. YOU DID A GOOD JOB. YOUR DAD MUST BE PROUD OF YOU !!! IT SHOULD NOT BOG ON A FAST THROTTLE,A FEW THINGS CAN CAUSE THIS,THE FLOAT LEVEL IS TO LOW,DOES IT BOG WHEN GOING AROUND A CORNER ??IF NOT THE FLOAT LEVEL IS GOOD. IF THE TIMING IS RETARTED THAT WILL CAUSE A BOG. TRY TO ADVANCE THE TIMING 3 OR 4 DEGRESS AT A TIME,FORGET ABOUT WHAT THE SPEC IS.IF IT STARTS TO PING YOU HAVE GONE TO FAR..BRING IT BACK.NO PING ALOWED.. GAS TODAY IS REALLY BAD. SEE IF THAT STOPS THE BOG.TRY SOME HIGH TEST FUEL.IS THE FUEL IN THIS TRUCK OLD ???THOSE LAST 2 QUESTIONS MAY SOUND STRANGE,BUT YOU WILL BE SUPRISED WHAT GOOD AND FRESH FUEL WILL DO FOR ENGINE .I HAVE A RACE CAR THAT I AM ALWAYS HAVING PROBLEMS LIKE THIS.. GET BACK TO ME ON MORE INFO IF YOU NEED IT..BY THE WAY,[[PLEASE RATE THIS ANSWER]] WHEN LEAVING THIS SITE. THIS WILL HELP ME. THANKS AGAIN TOM.
