Beware of multiple problems as you read here...
I was driving home from work friday and the truck acted like it was running out of gas. Coasted to the side of the road and after several attempts it restarted, chugged a bit, and continued on fine. About 1/4 tank of gas at this point. I ran a few additional errands - pushing the low limit. Today I adjusted the choke, idle circuits, timing and dwell. I went for some gas and I ended up stranded. Ironically, I took out the lawnmower's gas can before I left to get gas. This time it wouldn't start but for a second. I put about 8 gallons in and still had the same problem. When the throttle is opened - not running - there is no gas squirting. I disconnected the line to the fuel pump and only a small dribble comes out. Shouldn't the gas come out as if being siphoned? What does the pickup look lilke inside the tank? Any screen in there? Any suggestions would be appreciated.
1970 302 2V

 

try blowing air into the tank through the line. it sounds like you may have something in it. there wouldn't be a screen because there's no way to get to it. that's what mine did, i blew out the line and it's worked ever since.

 

There is a short length of flexible line under the tank, under the cab -- under the driverside seat. When this gets old, it swells and can stop off the flow of gas. If you are lucky that is your problem.

Take off that piece of hose and blow in the tank -- have a friend observe. Should get a decent flow of fuel under the truck. If not, next step is to take the tank out and rinse it out a few times with fresh gas. Take the fuel line off of the top of the tank and GENTLEY blow into the opening with compressed air. There is some controversy, but I thnk there is/was a screen at the bottom, on the end of the lead pipe which extends down into the tank. It gets crudded up. Once you have gas coming out of the tank, you can re-assemble. (FYI -- its not hard to take out tank, but is a 2 man job -- take the seat back off first)

Others places that things fail include the hard line that runs along the frame rail up to the fuel pump. It can get plugged too. Compressed air, pieces of wire etc can get it unclogged. For a more radical solution or if its got a leak, try inlinetube.com for stainless replacement.

Finally, no the tank may not siphon on its own -- especially if the gas cap is not letting air in. Did you happen to notice if there was vacuum in the tank when it died? You need to have a vented cap.

Good luck

 

Steve, Gas should flow at a pretty good rate out of the line. I agree with checking the rubber, and blowing air back into the tank. Remove the gas cap, the line at the pump that goes to the tank, and blow air from the pump back into the tank. Check the flow at the pump first, I presume you were referring to flow at the carb.

John

 

John,
No, I was referring to the line from the tank to the pump. Just a dribble there. The line from the point at the fuel pump back to the tank is new, steel tubing but the pickup tube inside the cab is original. I will pull that and inspect.
There was no vacuum in the tank due to the type of cap and I had it off putting gas in.

 

Not sure if simular, posted problem with fuel flow after i had emptied the tank to make some improvement. At the advice of another member, used compressed air and guardedly forcing air thru the filler neck to prime the tank. Suggest disconnect at the rubber section under cab for initial test in event there is residue. May be worth a try. Wonder if the cap could be the problem.

good luck,
dave

 

I've replaced the rubber line under the cab when i had this same problem. I now have a filter in its place. Keep crap from getting in to the pump.

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Update... I pulled the rubber hose at the bottom of the tank and routed it into a 2 gallon bucket and blew into the filler neck and received quite a lot of debris and some water. After emptying that, I repeated the process and still got some but not nearly the same amount. I noticed that once I started the pressure/siphoning that the gas would continue to flow until I plugged the line and it would dribble and stop. Must not be a large enough diameter to create a differential pressure great enough to initiate a siphon on its own.
This still didn't solve the problem so I checked the fuel filter which could be blown through as easily as a straight pipe (from either direction) and I popped the top off the carb to discover a dry bowl. I pulled the float and needle valve, cranked it over and was rewarded with a stream of fuel. Reassembled the carb and all is well.
The filter is a NAPA screw-in type at the carb but I guess I expected it to be a stone type with a little more resistance than that. It could have been a stack up of tolerances with the reduced flow from the tank and the slightly restricted float needle valve. My concern is that it will happen again - far away from my tool set. No, my greatest concern is that a bowtie will see me and offer to help

 

Put the fillter before the pump "Fram G2"
Maybe a hunk of crud was hanging up the float and when you pulled it it cleared but ither way the filter before the pump will not hurt.

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Steve, I had basically the same with my blue truck. I pulled the tank and rinsed it out with gas and haven't had that problem again, 18,000 miles later.

John

 

John,
That's good to know. When I took the lawnmower's gas can to get filled, still thinking I was out of gas, I noticed the liner sloughing off. It is a 5 gallon Jerry can and I could see the liner very easily. It made me throw away the can and wonder how bad the truck's tank could be. I will pull it and rinse it though as a precaution.

 

Before you put it back in go to the hardware store and pick up a box (50 or 100) of 1/4 inch of nuts. Pour them in the fill hole after you've taken out the "sending unit" then with two people slosh the nuts around in the tank. This will scrub off any loses crud inside the tank. then pour out the nuts rinse and reinstall the tank and sending unit.

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