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part to full throttle hesitation/bog

Dave 454
I love my Chevy Chevette!
Posts: 1
Joined: 02/14
Posted: 02/11/14 10:47 PM

I just bought a 1986 chevy c 3500 quad cab dually with low miles! I bought it 200 miles from home!whet acrost the street ate then trveled 5 miles in light city 35mph trafic with no issues! Then we hit the highway and I got angry! the truck nearly dies at half throttle and full throttle! If you feather it lightly you can get it moving but as soon as 1/3 throttle it falls on its face! The dealership was closed and no help to be found! I nursed it home under 50 and havent figured out what could be wrong! If I jam the gas on at a stop it takes right off for the most part then dies down and almost stalls if you let up it picks up but only pre 1/4 throttle! Pleas help with any ideas I really dont want to have to turn it in on a lemon law!  

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My first time was in a Chevy
Posts: 245
Joined: 10/13
Posted: 02/12/14 08:03 PM

first thing it probably has a DIRTY FUEL FILTER.  and that truck model might have two of them.. one in the carb.. behind the inlet nut.. please use 2 tools to loosen the fuel lines.. a 1" wrench and probably a 5/8 tubing/flair nut wrench..

the other fuel filter might be inside the frame rail under the cab..  either of those could be clogged.. you could have a fuel delivery issue with sediment in the fuel pump check valves..

you can actually monitor the fuel level in a quadrajet by using a thin piece of plastic no more that 3/16 wide by 1/8 thick and 3 inches long.. make a ZERO mark 39 MM from one end.. thats 0 on quadrajets.. you can in the slot at the back of the choke blade.. drop the plastic stir stick onto the top of the float there.. and monitor the fuel level..

 End  39MM      |O|||5|||||10||||15||||20 upper end..32nds of an inch or MM

if you slowly accelerate the engine and the float level drops you have a fuel delivery issue .

Quadrajetchokepulloffs Zps1a6a506a

please.. also check that the primary choke pull off works.. and that the secondary chake pull off works and is properly connected to the vacuum switch in the air cleaner housing..

if the primary choke pull off is disconnected or leaking vacuum. the secondary air door will be too easy to open and the truck won't run properly.

i normally recommend that with a cold engine the carb fuel inlect gets disconnected.. i extend the hard line wit some soft fuel hose and extending that into a 2 or 3 liter plastic soda bottle. then have somebody crank the engine for a timed 15 seconds.. you should have almost a pint of fuel.. and each pulse of the fuel pump should be the same..  

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My first time was in a Chevy
Posts: 245
Joined: 10/13
Posted: 02/13/14 08:43 AM

oh.. by the way.. i can just imagine driving an 86 into a dealership.. the techs all looking for the scan tool port..  if it as a 305 or a 350 model.. it would have one.. not that 454 version.  let us know what happens...

this might help with the fuel pump install...

preset the engine to #1 compression stroke TDC..  this positions the push rod eccentric at minimum extension.. so you don't have to fight the pump lever spring..

Chevyfuelpumpinstall Zps7347c8d5  

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I mow my lawn and find Chevys
Posts: 2253
Joined: 07/08
Posted: 02/14/14 03:15 PM

Sounds right Wayne.
I had a couple of cars do the exact same thing.
One had a clogged fuel filter and the other had
a bad fuel pump.  

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My first time was in a Chevy
Posts: 143
Joined: 11/11
Posted: 02/15/14 02:45 AM

sounds like a possible vacuum leak too?  

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