Help/suggestions trouble shooting no fuel flow problem

[Dave_Kriegel]

New piston rings, new coils new wiring new carb BUT NO FUEL FLOW Before I installed the carb on a car that has been sitting for 45 years plus I put fuel in the tank ( 5 gallons) to flush the lines. Carb is off Copper fuel line has and gate valve on 1/8? inch copper line. Buy no fuel flow out the line to carb. Put high pressure air at carb intake copper line and hear bubbles in the fuel tank. Ran 8 inch wire past gate valve line there is open Gate valve checked it does stop flow. So my question is any more trouble shooting suggestions? Before I run all new fuel lines

[Tom Hicks]

Just run new fuel lines, put in a fuel filter, drive on!

[Ruxstel24]

Could be rust/debris in the tank or sediment bulb, plugging up and open enough to hear bubbles.
Try opening the drain on the sediment bulb and see if anything is there.

[Dave_Kriegel]

Good idea, take off sediment glass bulb and clean it out see if any fuel gets to the sediment valve Time to suck gas out of the tank

[DickC]

I would follow up on the sediment bowl suggestion. The is a wire mesh filter there that could flap up with air pressure from the output side but not let the gas drain normally through it to the output line. Just thinking.

[Peter, Memphis TN]

Dave, your profile shows you have a 1921, and an earlier post says your new project is older. Either way, that means the fuel tank is under the seat. Right so far?

There is a solid brass combination shutoff valve/sediment bulb under the tank, if original. But your post says something about a "glass sediment bulb." If so, that's not original, although it might be perfectly OK.

The original sediment bowl is often called the Potato, due to its shape. It consists of an egg-shaped bowl, with a valve built in to the top, and a drain petcock on the bottom. On the side, there is a big removable part, with the output consisting of a hole in it.

Here's the usual problem: The output fitting has a very fine screen in it. It doesn't take much to block the screen. Old gas turns to varnish, and that can do it. After all, it's all gravity -- no fuel pump.

Removing the output fitting can be very hard. Sometimes you have to put a big wrench on it and crank so hard you can pull the fitting loose from the solder on the bottom of the tank. If you want to remove it, place your wrench so it's almost alongside the body of the potato, and apply pressure by squeezing the wrench together with the body, applying as little pressure to the tank fitting as possible.

In extreme cases, you might have to drain the tank and remove the potato altogether. This can also require enough pressure to damage the fitting on the tank. It's 1/2" pipe threads, and probably has very old and very hard sealer on the threads. Again, you risk damaging the fitting on the tank.

If you remove the potato, rinse it out very well and then apply heat, to loosen the output fitting. Obviously you can't do this when it's on the tank!!

It's normal to find the screen so badly gunked up that it can't be cleaned, even with MEK or Lacquer Thinner. The screen is available from suppliers, and it's soldered in place.

Once you are sure the fuel is entering the potato from the tank (because it pours out of the drain petcock), and it can get through the screen in good quantity, then your answer is in the fuel line.

DO NOT replace the line with copper tubing!! The original was brass tubing, which withstands vibration without eventually breaking (like copper will do). But it's hard to find. So, use 1/4" STEEL line, which is available in many lengths at any auto parts store, under the heading of Brake Lines.

The normal test for the fuel delivery system is to place a fairly large can under the carburetor, and open the drain valve on the bottom of the carb. Let it run until you get about a pint, and look to see that the flow continues steady for that long. If so, everything upstream is OK. If it gushes a little then reduces to a trickle, then your system is clogged, and the 'gush' was what had accumulated in the bowl, a drop at a time.

All that's left is the needle valve and jets in the carburetor, but if it's been recently worked over, only dirt in the orifices would be a problem.

By the way, I don't agree with putting a fuel filter in the line. The outlet from the potato is only a couple of inches above the carb input, so you get very little pressure from gravity. Most filters, if even a little clogged, won't pass enough fuel when you're down to a couple of gallons in the tank.

[Original Smith]

Make sure your vent in the gas cap is there and open.

[TWrenn]

Certainly can't add any more advice than what Peter did above. Former fuel issues of mine, I followed the same steps. The fine mesh filter in the potato is often the culprit, next to a plugged fuel line itself. Also there could be crap right at the outlet hole inside the tank, but removing the potato in all this work will determine that.

As for fuel line, just go to your favorite vendor and order a steel one, it'll be pretty much the length you need, maybe a wee bit longer. Langs has them in both steel and brass. Just get the steel one and be done!

Good luck!

https://www.modeltford.com/item/2909.aspx--Steel line

https://www.modeltford.com/item/2909BR.aspx...Brass line...lots more $$!!

[Norman Kling]

Two cars I have worked on have had fuel lines so plugged up it was like they had been filled with epoxy. One of the two had a very dirty gas tank. The cars with the tank under the seat, you can buy a replacement tank for just a bit more than the cost of boiling out and sealing the existing tank. I replaced the tank. The only ones on which the tanks are not available are the cowl tanks on the 26-27 models.

What I expect is that there is a very small opening for air to pass through so you get the bubbles, but it either plugs with sediment or restricts the line so that gas doesn't flow. A partially restricted line will fill the carburetor bowl when the car sits with the valve open, but when you drive it a short distance it runs out of gas until it sits a while longer.
Norm

[Dave_Kriegel]

Thanks again to all I MAY HAVE found my fuel blockage problem ( I hope) see pics

[Norman Kling]

Dave, what are those pictures? What size is it? Looks like a filter.
Norm

[Mark Gregush]

It is a glass bowl and filter. While the photos are dark and small, the filter looks pretty plugged up. My OP; you need to pull the tank and clean it or it will just be a constant fight to keep clean and fuel flowing. Even small bits can keep the carb float valve from closing.