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Rochester Quadrajet Problems

  
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Rochester Quadrajet Problems

 
tauger1205 tauger1205
New User | Posts: 1 | Joined: 11/12
Posted: 11/22/12
09:23 PM

I have a 1979 chevy k10 with a the stock Rochester Quadrajet. just today it was acting up... i could only give it little throttle or it would bog to nothing almost instantly it seemed like it was flooding out. but i could baby it up to speed. after about 5 miles of that i was mid way up a hill when flames came out of the exhaust and it stalled. it started back up made it up the hill then it stalled again. good thing i live at the top of that hill... i just had it rebuilt about a year ago maybe alittle more. the choke on it has been sticking a bit too but it usally shuts off after alot of driving. the choke is electric. it didnt seem like it was on while all this was happening. the truck barely sees the highway, before all of this happend i was on the highway but it ran normally. it never really seemed to run great always felt like it was robbing alot of power and it back fired most of the time every time in fact if say i  was in 2nd and let off the throttle (4spd with granny low) saddly i dont think that the shop will warranty it. is this a common problem for the quadrojets? i have herd of many people having issues with them but it is pretty freshly rebuilt. sorry for the novel. any suggestions or comments will be appreciated thanks  

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 11/23/12
02:12 AM

why not try a full flow fuel pump test first.. make sure the fuel pump or fuel system is not the cause...

cold engine.. unplug the BAT wire from the HEI cap...   holding the filter nut with a 1" wrench and loosening the tube nut with a 5/8" tubing wrench..    shove some fuel line or something like 7/16" id clear vinyl hose over the end of the fuel line...  extend it into a clean clear 2 or 3 liter plastic soda bottle...  have a friend crank the engine for 15 seconds.. while you observe the fuel pulses into the bottle.. each should be nice and full.. same size as the others...

please be careful when reattaching the fuel line to the carb inlet ..try not to cross thread it..

you might want to also check the fuel filter thats hidden in there.. just replace it..  again.. start threads by hand.. it should thread all the way in with your fingers..  5 or 6 turns.. not 5 or 6 flats..

you should have about half a quart of fuel in the bottle after 15 seconds of cranking..  

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 11/23/12
08:07 AM

i should explain. that when the fuel level in the carb drops.. the air fuel mixture leans out..  lean mixtures burn slowly.. so when the intake valve opens at the end of the exhaust stroke..  there is still flame in the cylinder... so it backfires up the intake and through the carb...


this is why i am asking you to run a full flow fuel system test.. to see if the fuel system can keep up with the volume..

people have also found pin holes in the metal fuel lines. between the tank and the pump..  

cracked rubber fuel hoses between the tank and the pump..

missing or clogged strainer socks in the tank on the end of the sending unit tube..

lastly... a rare one but still happens... failure or incorrect connections of the fuel evaporation system...  where there will be a vacuum formed in the tank by the purge system..  you will notice this as when you go to add some gasoline.. when you remove the cap.. you get a terrific whooshing sound as air rushes in...

there are other things to check.. but this is just the first test... doing the others first does not make sense..  as you could change the carb and the distributer.. all the spark plug wires.. a bunch of other parts... if you don't have enough fuel volume.. you won't have a decent running truck when you request more power requiring more fuel volume...