No gas getting to carburetor
 

Greetings, 2500 panel, 305E, SM420.

Real strange situation. Went to start it, nothing, would crank, no gas in clear fuel filter. I have had too many fuel pumps go bad due to ethanol gas so I changed the fuel pump.

Still nothing. I checked the fuel line under the truck and I noticed an rubber elbow about 5 feet from the tank. It was original and dry rotted and slow drip of gas.

Ok , I thought I found the problem. Installed a new rubber hose, still nothing.

Put another new fuel pump on with another fuel filter, still nothing .

Checked the gas tank for gas , its completely full.

Removed one end of the fuel hose where it connects to the inlet of the pump. I blew compressed air into the hose and a friend witnessed air and bubbles coming from tank fill spout .

Still nothing, cranks 15 seconds at a time, no fuel enters the completely new clear filter.

I am baffled.

Re: No gas getting to carburetor
 

two things likely. First, have you checked the under-cab fuel filter? It looks like a coke can under the passenger side of the truck. If so, it may need priming.

I just had a conversation with another member about this. When mine went out, I had to prime the fuel pump. It took a while. I hooked up a rubber hose below the pump and stuck a funnel in that. The total had to be above the gas tank's level. Then i poured gas in the funnel and let it clear out the air between the tank and the pump.
Once it was cleared and running back to the tank, plug the hose back in the fuel pump and bob's your uncle. May have had to prime ahead of the pump too once I got it back together, but I can't remember.

Never had to do this with another car or truck, but for some reason it was necessary on mine.

Re: No gas getting to carburetor
 

I checked pretty carefully, I did not see anything the size of a can under the truck. There is a metal line that comes out of the tank, the line goes accross the truck to the passenger side. That's where the rubber elbow was. Then It continues up to the engine area where it becomes rubber again. Then into the pump.

Re: No gas getting to carburetor
 

First thing is to look down throat of carb and operate throttle to see if there is gas squirting in there. No gas? Report to us and See below.
Take off line to pump intake. install a hose at pump intake and put hose into a gas can on the ground (no filter). Take off pump outlet and run it into a container. Take off center tower distributor wire. Crank motor for 15-20 seconds and observe flow into container. Should pulse with good flow. No flow? Report back here. Flows good? reattach output to carb. Put plug wire back on, with pump intake still hosed to a gas can...... start motor. Report.
These tests will lead us to narrow the possibilities. Right now there are too many to start guessing. A testing plan of action is best.

Re: No gas getting to carburetor
 

Ok thank you , will do. Keep in mind, I have a clear fuel filter between the carb and the pump, and its completely dry.

Re: No gas getting to carburetor
 

I realize that. I'm waiting for your detailed explanation of what you discover. Don't mess up the test with a dirty gas can with old gas or use old non-fuel hoses. Don't use filters. Have the gas can near front tire, short hose. don't spill has over motor. If you do, let dry.

Re: No gas getting to carburetor
 

Update, I had a manual siphon so I primed the line. Still nothing, crank for 15 second intervals, finally the gas made it to the filter and it started.

I have changed fuel pumps before and this has never been a problem.

Can the fact that the line was empty from changing the rubber elbow caused this problem?

What are you supposed to do if you run out of gas?

Anyway, thanks for the advice.

Re: No gas getting to carburetor
 

What exactly is a "manual siphon"? A bulb like on a boat tank? or a funnel? Good work, glad you got it started. You just did not crank long enough with choke closed. The fuel pump with suck it pout of the tank, no sweat. All I can say is I have run out of gas. I have also installed a new tank and all fuel lines in my 305 V6 and it started without priming. Just cranking with choke closed and pumping gas pedal. My filters are always before the pump.
I don't dispute other folk's experience.

Re: No gas getting to carburetor
 

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 ?

Re: No gas getting to carburetor
 

Even though you "siphoned" it seems it still took a long time. Several 15 second intervals is a long crank. Anyway, about the choke. We are talking about new fuel pumps and possibly no gas in hose or carb. The motor cranks with the starter. The pump is pumping slower than even at idle. So when gas does finally get into the carb/manifold/combustion chamber, you want a good rich load so motor starts as fast as possible to begin pumping faster. So having the choke closed gives you that rich shot. Then you gradually open it, as you know, as motor stabilizes. Having it closed has nothing to do with more pump suction per se. It is just part of a dry start procedure that I thought we were all discussing.

Yes the choke has an impact on gas. Air is part of the gas mixture.

Running out of gas may take the same procedure.

Some say they prime, some say they don't. No argument. What works is good.

Re: No gas getting to carburetor
 

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.

Re: No gas getting to carburetor
 

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.

Re: No gas getting to 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.

Re: No gas getting to carburetor
 

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.

Re: No gas getting to carburetor
 

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

Re: No gas getting to carburetor
 

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).

Re: No gas getting to 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.

Re: No gas getting to carburetor
 

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

Re: No gas getting to carburetor
 

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

Re: No gas getting to carburetor
 

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?

Re: No gas getting to carburetor
 

The tank is an original suburban fuel tank. The one with the tire cut out is not reproduced. Here are a few photos I got from another forum, showing the hose connection.