Re:1976 Chevy van fuel pump

Slowpoke

Well-known Member
I got the fuel pump in OK with the grease trick holding up the push rod and changed the Quadrajet carb filter. When the engine started, fuel began to rise up
out of the carb at the accelerator pump and around the plates. Is the cause a stuck open float? Or something else? The van ran poorly before the fuel pump was
replaced, like it was out of gas every few miles. The filter was distorted and was stuck in the fuel nut with rust on it.
Any ideas?
Thanks
Slowpoke
 
carb rebuild if the throttle plates shafts aren't shot. (problem on 4barrel carb) 2 barrels last good!
 

I know you don't want to hear this... Check the fuel pressure I have seen replacement pumps (airtex) peg a 30 psi. gauge...
 
(quoted from post at 01:19:45 03/02/21) I got the fuel pump in OK with the grease trick holding up the push rod and changed the Quadrajet carb filter. When the engine started, fuel began to rise up
out of the carb at the accelerator pump and around the plates. Is the cause a stuck open float? Or something else? The van ran poorly before the fuel pump was
replaced, like it was out of gas every few miles. The filter was distorted and was stuck in the fuel nut with rust on it.
Any ideas?
Thanks
Slowpoke

When you changed the filter a piece of debris may have found it's way to the needle and seat.
 
When you changed the fuel filter in the carb some
small particles got dislodged and made there way into
the float needle and caused it to leak by. Here is a
little mechanics trick that might work and save you
from taking the top off the carb. Pinch off the large
hose between the fuel pump and frame with a vise
grip. If you are worried about damaging the hose use
a piece of flat iron on each side of the hose..fender
washers would work. Start it up and run it until the
carb runs empty, then open the hose and start it.
Hopefully with the float opening the needle wide open
it will flush the debris out of there and all will be fine. It
has worked for me more times than not. Secondly if
you put Teflon tape on the line fitting or the filer nut
threads chances are you will have more problems like
this and you will need to pull the filter out and clean
that all out of there with carb or brake cleaner. The
nut that holds the filter in the carb should have a
gasket so it or the flared tube should both seal fine
with out the aid of anything else.
 
Probably trash in the needle valve. Try disconnecting the large rubber line from the fuel pump, start it up, run it until it dies, then reconnect the line, crank it back up. Maybe that will flush whatever is in the needle valve.

Those are also known for the float sinking. The new pump may have brought the pressure back to where it needs to be and is over riding a weak float. Easy job to replace it, just be careful not to drop any screws.

Whatever you do, don't let anyone talk you into "Put a Holley on it, that'll fix it". Horrible carburetors!!!
 
Steve,

Everytime I see "replace with holley", I think the same. I did that once. Went back to a Q jet with no regrets. They seem weird, bbut are rather nice once you get used to them. I buy every cheap one I find. I got one for a buck at a car show, with the electric choke! It worked nicely, but looked ugly.

D.
 
Yes stick with the Q-jet. Sounds like needle valve issues. I always replaced the float they gradually sink enriching the mixture. The spread bore Holley is a nightmare and the regular Holley is a good race carb, but not good for the street. I usually run an added filter with a Q-Jet and toss the original filter.
 
Years ago I would buy a Q-Jet (Chevy Truck) and a non-computer HEI when I went to a swap meet. Oh and a Powerglide for the drag car.
 
I never use Teflon tap on anything but tapered threads. I have found where others put it on straight threads and it does no good.
A new seal was used on the filter nut.
 
I said ..IF.. you used it. Just giving ..ideas.. as you
requested. Some may not know they are asking for
trouble by doing, it appears you do not fit in that
group. Have not looked to see if this was suggested
but you might want to ..slightly.. pressurize the fuel
system by putting compressed air in the tank with a
rag wrapped around a blow nozzle. This may help
you find where the water you found in the filter
migrated in. Check the fill pipe and connections for
sure.
 
Another fan of the mighty Quadrajet; no glamour, tons of adjustability.

I agree with the others that a piece of debris probably inadvertantly got in there during the filter change. Worth checking out the float for deterioration or fuel absorption. Make sure you have the right float setting; some of them are relatively high or low depending on the air bleed configuration. Also there are two different length of floats IIRC.
 
Probably don't put 50 miles a year on van. Probably shouldn't even keep it at $150/yr tags and insurance.
It has 158K on it. so not much wear.
 
Float is metal (copper?) and has no fuel inside. But lots of stuff on the bottom of the well. I had to remove carb from engine: it was impossible to get top off working under the dash. I'll clean it up and put a new kit in it. Or take it to a carb shop for $100. We'll see.
 
(quoted from post at 09:53:41 03/02/21) Probably trash in the needle valve. Try disconnecting the large rubber line from the fuel pump, start it up, run it until it dies, then reconnect the line, crank it back up. Maybe that will flush whatever is in the needle valve.

Those are also known for the float sinking. The new pump may have brought the pressure back to where it needs to be and is over riding a weak float. Easy job to replace it, just be careful not to drop any screws.

Whatever you do, don't let anyone talk you into "Put a Holley on it, that'll fix it". Horrible carburetors!!!
he only problem with a Holley is people think they can learn how to tune it by drinking beer and looking at it. Holley's are universal carbs and must be tuned for each application. There is a terrific book called "How to tune your Holley carburetor" that solves all the problems people encounter.
 
Sometimes the carb needle and seat will have a piece of trash in it. It's good practice when removing a carb to keep it level and set it down level. That was a common problem years ago on carb equipped engines.
 
Is the ball under the needle seat supposed to come out?
Turning the carb upside down and tapping does no good.
 
(quoted from post at 09:47:48 03/08/21) Is the ball under the needle seat supposed to come out?
Turning the carb upside down and tapping does no good.
his is where I read between the lines or you are asking a completely different question as related to the float valve.. Their is no ball under the main float needle/ seat. How ever their is one under some of the Power Jets as they changed over the years of production. That will come out . Here is a manual for the carb. " https://www.carburetor-parts.com/assets/manuals/quadrajet_carburetor_manual.pdf "
A model number would have been a real help in answering your questions as well , but the manual should tell you more than I can . Since it's been over 40 years since I have played with one.
Hope this is of some help .
 
you can use a hacksaw blade on the pump rod to hold rod up when putting on the pump. all carbs use the same principles, as different brands go, I have done enough, of each brand, to know all of there differences , you will probably have to go through it, I do not like the Quadra Junk carbs that much, because of the complexity of the system, compared to other simple systems like the Holley brand. just my intake on it.
 
The quadrajet is quadra what those holleys are. And very
simple also , not like a Holley that u have to be constantly on
repairing leaks.
 

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