QJet Prime Issue ?

[54blackhornet]

I had the original QJet on my 71 GMC rebuilt twice by two different shops. I run non ethanol gas always. If the truck sits for any length of time it will not start unless you pump the gas pedal, last count 16 times. The well plugs where resealed both times. Looking for ideas on how to correct...thanks

[weim55]

Are you certain the choke is functioning properly and adjusted correctly?

Steve weim55 Colorado

[HO455]

I would let it sit and then I would remove the top of the carburetor to see where the fuel level is before trying to start it. If it is up where it should be then it's likely your accelerator pump has failed. With the second choice being the check valve not working correctly.
If the fuel bowl is empty or very low then it is likely one or more of the well plugs is leaking.

[JMac11]

Correct fuel filter installed correctly in the fuel fitting also a good thing to check

[54blackhornet]

Thanks guys ! Can you see fuel by looking inside the throat ? I didn’t think it would start if the accelerator pump was not functioning. Running a in-line filter and the one inside the fuel inlet....appreciate the help

[AussieinNC]

Two things come to mind:

Fuel pump check valves are leaking allowing fuel to drain back to tank when shut off

You do have the thick insulating gasket between the carb and manifold ?....if not, the fuel will boil away after shut down

I usually run an electric fuel pump on my own trucks...wired thru a shut off switch that hidden away...helps deter the "midnight spares" crowd....

[truckster]

Based on your observation, I would strongly suspect an issue with the choke rather than a lack of fuel in the bowl. If you're pumping the gas and it starts, that indicates there's fuel. If it only starts after it cranks a while, that indicates a lack of fuel.

When it's cold, take the air cleaner off, and without cranking it, depress the accelerator pedal and release it. The choke plate should snap closed and the throttle should be on the high idle cam. If that's not the case, your choke is either bad, disconnected, or incorrectly adjusted.

[100%Chevy]

A big part of your problem is probably evaporation.
If mine sits for more than week,I have to prime the float bowl.
Takes about 5 ounces in the top vent hole.
Same problem with my Edlebrockes.
Mike.

[El Dorado Jim]

Originally Posted by 54blackhornet

I had the original QJet on my 71 GMC rebuilt twice by two different shops. I run non ethanol gas always. If the truck sits for any length of time it will not start unless you pump the gas pedal, last count 16 times. The well plugs where resealed both times. Looking for ideas on how to correct...thanks

I run an edelbrock carb on my truck, have the same issue, i put an inline electric fuel pump on a switch, I use it for a minute or so when my truck has been sitting for a week or more, gets gas to the carb quick, then im not cranking forever until gas gets there from the mechanical pump

[54blackhornet]

Thanks fellas ! The truck will only start after pumping the pedal numerous times, even if it sits overnight. I will check the choke, it’s divorced type...Jack

[Ol Blue K20]

Accelerator pump check ball not sealing. I had the same problem then I bough "Cliff Rugles " quadrajet book. I learned a lot and how to fix it. Use a old check ball and tap a few times with a punch. It forms a new seat. What a difference it made.

[54blackhornet]

Thanks OldBlue for your help.

[HO455]

Originally Posted by 54blackhornet

Thanks guys ! Can you see fuel by looking inside the throat ? I didn’t think it would start if the accelerator pump was not functioning. Running a in-line filter and the one inside the fuel inlet....appreciate the help

You can not see the fuel level in the float bowl from the outside on a Qjet. You however can see how well the accelerator pump is working by looking down the primary bores and winging the throttle open. You should get two good solid streams shooting across the bores. Weak streams in conjunction with a choke plate that is not fully closed before the engine starts can cause the symptoms you are experiencing.
If the pump seal lip has failed or as Old Blue K and I have said the check valve is leaking you will have a poor accelerator pump shot. So if the pump shot is poor the first step is to see if you have fuel in the float bowl and that means pulling the top off of the carburetor without spilling fuel out of the carburetor. I usually just do this with the carburetor still bolted on the intake manifold.
If you have enough fuel in the float bowl then it is highly likely the pump lip seal or the check valve is the culprit.

[HO455]

Originally Posted by AussieinNC

Two things come to mind:

Fuel pump check valves are leaking allowing fuel to drain back to tank when shut off

You do have the thick insulating gasket between the carb and manifold ?....if not, the fuel will boil away after shut down

I usually run an electric fuel pump on my own trucks...wired thru a shut off switch that hidden away...helps deter the "midnight spares" crowd....

A Qjet won't drain back through the fuel pump as the needle and seat are not on the bottom of the float bowl.

[rsgt]

I had cliff Ruggles build my Quadrajet. If it sits for 3 or 4 days it has to crank quite a bit. 1 or 2 days and it starts right up.

[randy500]

Your problem is probably evaporation but it could be leaking back through the fuel pump if you have a windowed seat in your quadrajet.
It could be a leak where the seat screws into the bowl.

You can vacuum test the needle and seat by applying vacuum to a test fitting at the carb inlet.
You can also vacuum test the fuel pump at the inlet, should hold vacuum.

Parts changing possible drain back cures to be used with or without vacuum testing

1. Remove clip on needle which seals the seat regardless of float position.
2. Install fuel filter with built in check valve.
3. Install non windowed seat.

[Ironangel]

Originally Posted by truckster

Based on your observation, I would strongly suspect an issue with the choke rather than a lack of fuel in the bowl. If you're pumping the gas and it starts, that indicates there's fuel. If it only starts after it cranks a while, that indicates a lack of fuel.

When it's cold, take the air cleaner off, and without cranking it, depress the accelerator pedal and release it. The choke plate should snap closed and the throttle should be on the high idle cam. If that's not the case, your choke is either bad, disconnected, or incorrectly adjusted.

^^^This!^^^