No gas getting to carburetor

[George Bongert]

Originally Posted by zoulas

Yes a bulb. What difference would having the choke open or closed make, the choke only restricts air flow. It has no impact on gas. No ?

Greetings, zoulas!

The choke does indeed have an impact on gas. The choke not only restricts air flow, it enriches the fuel to air ratio for engine cold starting. That is why older engines that are not equipped with modern fuel injection systems run rough and smoke black with the choke closed, or almost fully closed. Having the choke closed can have some very adverse effects on the engine itself if the engine is only run for a short period of time without being allowed to warm up to operating temperature, since the very rich fuel to air ratio will wash down the cylinders, and dilute the oil in the crank case. So, yes, the choke does have an impact on gas. Try driving your truck with the choke partially closed and watch your gas gauge plummet toward E very rapidly if you think that the choke has no effect on gas.

[zoulas]

I thoroughly appreciate you feedback but in the interest of learning something (for me) how does it do that? It seems the manual choke is simply a lever that closes the butterfly on the top of the carb (choke) and actuates the accelerator pump to get some extra gas in the carburetor. I thought the 'richness or lean-nes' of the fuel/air mixture is controlled by the screws at the base of the carburetor.

[FetchMeAPepsi]

Originally Posted by zoulas

I thoroughly appreciate you feedback but in the interest of learning something (for me) how does it do that? It seems the manual choke is simply a lever that closes the butterfly on the top of the carb (choke) and actuates the accelerator pump to get some extra gas in the carburetor. I thought the 'richness or lean-nes' of the fuel/air mixture is controlled by the screws at the base of the carburetor.

Those only control idle. The butterfly closes the airflow into the carb. Less airflow = more rich fuel/air mixture = start motor on less gas because it's not diluted with air.

The accelerator pump is run by the foot pedal.

[AZKen]

The choke is part of the "cold start circuit". We not only have a cold start we have a possible empty carb bowl and lines. Closing the choke is how you start a cold/empty motor. The accelerator pump delivers the rich shot as described by me and Fetch. There is not much vacuum/venturi effect at that point.

The needle valves are for idle circuit dribble and main circuit. The main circuit takes over as you press throttle/open the throttle plates and create the venturi effect. The main jets and the rest of the main circuit does add some air to the gas to help in the atomization (air/fuel mixture at/in the venturi). I am not an expert but that is how I would describe it in general.

The richness and leanness is controlled by the valves and jets as you say. WE are ONLY talking about the cold/dry, after new pump, start subject of this post. Not the general running after warm up and on the road performance tuning.

[zoulas]

Incredible responses, you are all truly gentlemen with tremendous knowledge.

[James]

It still sound like you are not getting enough fuel. I think you have a plugged main metering system. I could be from the sitting for a long time (old fuel can cause this crusty build up) or something had gotten into the internal passageways restricting the fuel flow to the boost venturis. I would disassembled the carb and check that portion of the circuit from the main jets to the boost venturis. You might get lucky and it only the main jets plugged (being they are in the bottom of the fuel bowl).

[George Bongert]

Originally Posted by zoulas

I thoroughly appreciate you feedback but in the interest of learning something (for me) how does it do that? It seems the manual choke is simply a lever that closes the butterfly on the top of the carb (choke) and actuates the accelerator pump to get some extra gas in the carburetor. I thought the 'richness or lean-nes' of the fuel/air mixture is controlled by the screws at the base of the carburetor.

Greetings, zoulas!

Those screws at the base of the Carburetor only control the engine idle fuel to air mixture ratio. The actuation of the Accelerator Pump only squirts a little extra gas into the throat of the Carburetor during acceleration. Without that little bit of extra gas, you would experience a "flat spot" during acceleration, meaning that you would notice the engine temporarily "stalling out" or "hesitating" for lack of better terminology. The Accelerator Pump has nothing to do with getting extra gas into the Carburetor itself. Closing the choke forces the engine to draw extra gas into the throat of the Carburetor thereby enriching the fuel to air ratio for cold starting. Opening the choke fully too soon after starting a cold engine will result in the engine stalling, and operating the engine with the choke almost fully closed will result in excess fuel consumption, and the "washing" of the cylinders and crank case oil dilution that I previously described. Get a book on how Carburetors work, and you will have a better understanding of how they work, and have an effect on engine operation and fuel economy.

[zoulas]

Follow up question:

I have one rubber elbow in the gas line where it makes the turn from across the truck to going forward. That rubber elbow was original and dry rotted. I am thinking there may be another rubber connection going to the gas tank. How does the metal line connect to the gas tank? I cant imagine its metal on metal as that would be prone to breakage from flexing. Its in a place that's hard to see.

Thanks

[Funky61]

Here are some photos of the tank from a suburban. I'm not sure if yours has the cutout for the spare tire.

[AZKen]

Generally speaking there are two reasons for rubber hose. One is to enable removal of tank, like the filler rubber hose. The other is for vibration/movement, as you know. Generally if the tank and the fuel line are mounted to the same thing, like the cab or the frame, there is no need for rubber because in the frame mount example, the tank and the frame and the line move together. Rubber is needed when the line travels along some other part or it leaves the frame. Like when the line heads to the motor/fuel pump. The frame and motor are going to move independently of each other. Therefore a flexible line is needed there. I.E. rubber hose section.

In a 6066 truck, the tank is behind the seat. Mounted to the cab. The cab is mounted to the frame. The cab and frame "move" independently, So the hard line is attached to the sender and travels down thru a hole in the cab and towards the frame. The transition at that point needs a rubber hose from cab hard line to frame mounted hard line. Then the hard lines goes all the way to front and has the aforementioned rubber hose to pump.

Same general story, as you will notice, with brake lines.

If you are unsure or the factory used a hose, no problem adding, except it's another two leak points and Chinese rubber hoses deteriorate.

Maybe Funky can tell us or show a pic of any rubber on the hard line for a Burb, should be the same for a Panel. Also: what is the vendor and part number of that tank?