72 C-20 Help

[saddletramp]

Evening Guys my 72 chevy 350 motor Rochester carburetor i just got this truck awhile back to start it i have to poor gas into the back of the carburetor then after it runs for a while when i put it into gear it will move alittle bit then stall,s any idea,s on this ? Thanks Saddletramp

[LockDoc]

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There is a small filter under the large nut that the yellow arrow is pointing to. (or should be) I would start by replacing that. You have to disconnect the fuel line before trying to remove the fitting. Be sure and use a wrench on both the large fitting and the fuel line when removing and replacing the fuel line. Be very careful when screwing the large fitting back in, it has fine threads and is easily cross threaded. If you try to tighten it up when it is cross threaded you will strip it out. Any auto parts store should have the filter.

Your symptom can actually be caused by a few different things but this is the easiest to start with and it probably needs changed anyway.

LockDoc

[rpmerf]

to start it i have to poor gas into the back of the carburetor

In the quadrajet, the bowl need to be full for the accelerator pump to work. If my truck has not been run for a couple days, it takes about 10 seconds of cranking to fill the bowl, then pump the gas it and it fires right up. Dumping fuel in the carb, might just be getting you past that 'fill the bowl' part.

A couple things to consider here.
#1 - Make sure you press the pedal to the floor once before attempting to start. This sets the choke and the accelerator pump sprays fuel into the engine. I usually push the pedal down once every 1-2 seconds while cranking. so it will spray once the bowl is full.

#2 - Check that the accelerator pump is working. Get it running by itself to be sure the bowl is full. Pull the air cleaner. Open the throttle. You should see a stream of gas from each of the primaries as you open the throttle.

#3 - Make sure your choke sets when you open the throttle on a cold engine. Open the throttle all the way. The choke plate should close almost all the way. It should give you high idle also, ~1500 RPM in park or neutral vs ~750 with the choke off.

#4 - fuel filters and pump. LockDoc suggested changing the filter at the carb. While you are in there, I would put a hose on the end of the fuel line, and run the hose into a jar. Have someone crank the engine and watch the fuel come out of the hose. Should come out in strong pulses. Some other thoughts here. There is a fuel sock in the tank. If there is a leak between the tank and pump, it will suck air. You can run a fuel hose from the in side of the pump into a gas can and have it pull from the gas can.

#5 - stuck float. I've had this happen before. The float needle gets stuck in the float valve, so fuel cannot fill the float bowl. Usually the fix is to tap the carb body near the float valve with the handle of a screwdriver, while someone cranks the engine.

#6 - vacuum lines. A vacuum leak will cause a lean condition.

then after it runs for a while when i put it into gear it will move alittle bit then stall

Not sure if this would be spark or fuel. This is something that happens with not enough spark advance. I tend to check spark issues first as you can KNOW what the advance is. With fuel it is more of a guess / looking for clues as to whether or not it is right. Again, choke could be the issue here. Could be idle fuel and idle not set correctly. Could be a weak spark from a bad coil.


A good document on the quadrajet:
http://www.capitalcorvetteclub.ca/at...ng%20Paper.pdf

[saddletramp]

Awsome Guys I appreciate the advice ill get to work on your ideas Thanks Saddletramp