1957 filter sock in gas tank

[tfduda]

I suspect that I have an intermittent problem of fuel flowing from the gas tank to the fuel pump presumably due to something occasionally blocking the flow from the tank (see below for details). I want to replace the fuel filter sock in the tank to determine if this is the source of the problem (see photo below). How does one go about changing this filter and/or the line in the tank that leads to it?



Details and history:
I have had the car for just over a year. About a month or so ago, it had problems starting/idling and appearred to be starved for fuel. I diagnosed this by manually pushing the throttle arm on the carb and seeing no fuel flowing into the carb. After continuing to pump the arm, fuel eventually began to flow into the carb and I could get it to start and stay at idle. During the past few weeks, however, it has failed to start at all and continued pumping of the throttle arm doesn’t start the fuel flow into the carb. I figured this finally gave me the chance to trace the source of the problem by doing the following.

I first removed the fuel line going to the fuel filter and checked fuel flow through the filter (by blowing into the intake side of the sediment bowl). Flow through the filter seems fine.

I then put the end of the fuel line coming from the fuel pump into a jar and turned the car over a few times. Fuel only emerged in small spurts. I do not currently have a gauge to measure the pressure, but it clearly seems to be much lower than it should. I assumed this might mean a faulty fuel pump, but see below.

I reconnected the fuel line to the now empty sediment bowl and attempted to start it again. Given that the bowl was empty, I could see fuel enter it in small spurts as I turned the car over. As the fuel level in the bowl got higher, I could also see lots of bubbles entering the bowl. I took this to mean that the pump is pumping well but that low fuel flow to the pump was causing the bubbles. I attempted to start the car again, but had no luck and continued to see little if any gas going into the carb. And when I added the gas directly to the carb, it would turn over but then die. And so, I assumed that the pump is fine and that the fuel starvation issue is due to constricted flow somewhere between the tank and the pump. I realize that faulty fuel pumps are a common problem with low or no fuel flow on these cars. The pump was replaced in 2010 by the previous owner with a US fuel pump (or at least it has hex head screws and not Phillips screws holding it together). Nonetheless, given all the bubbles in the sediment bowl, I assume the pump is fine.

I had previously looked into the gas tank and it looks clean without corrosion but I thought that perhaps some debris in the tank is clogging the line from the tank. The car ran out of gas a month or so before the problem first arose and so I suspect that debris in the bottom of the tank may have been drawn to the fuel line. To test if this is the source of the problem, I bounced the rear end of the car up and down several times (to slosh around the gas in the tank) and then attempted to start the car. It started right up! Flow into the carb looks normal again and there are no bubbles going into the sediment bowl! I suppose it’s possible that the sloshing somehow dislodged something in the fuel line from the tank, but it seems more likely that the sloshing moved around debris in the tank where the gas enters the fuel line. And so I want to replace the sock filter in the tank to see if this fixes the problem of occasionally constricted fuel flow. If this doesn't sound right and someone has better insight of the source of my car's problem, I'm also happy to test further!

This page contains affiliate links for which I may be compensated. As an eBay Partner, and Amazon Associate I may be compensated if you make a purchase at no cost to you.

 

[74 Harley]

If you want to replace anything in the tank you must remove the tank. However, I believe you problem is going to lie with your fuel pump. You should have more than little spurts, and no air bubbles. Hook up a pressure gauge as well, I believe it should have about 4.5 lbs pressure if I remember correctly.

 

[tfduda]

Thanks for the info about replacing things in the tank--sounds like it might be easier to rebuild the pump! When I saw the spurts of gas, I figured the pump was to blame (especially after reading about problems others have had with their pumps) until the car started up and ran fine after I bounced the rear end and sloshed around the gas in the tank. Although I understand that the gas sloshing may have affected something else, it just seems that it would have dislodged something that intermittently affects flow from the tank and so that's why I worry about debris in the tank (though the tank looks pretty clean). Moreover, given it recently ran out of gas while idling, debris from the tank seemed a likely culprit.

I'll get a gauge and measure the pressure from the pump (although it'll be a few weeks before I'll be able to do this). Currently it's starting up and staying running with no bubbles in the sediment bowl and flow into the carb looks great and so I assume the pressure should be normal if it continues like this. When it's starved for fuel again, I'll check the pressure then too. Am I wrong in assuming that if there is constricted fuel flow to the pump that it will pump small spurts of fuel and air? And will the pressure read normal if the pump is fine and the fuel flow to the pump is constricted?

Any advice on a gauge to get?

 

[74 Harley]

Unless you are nearly out of gas or have a cracked or loose fuel line you should never get air. There's also the possibility of a sticking float in the carburetor, or crud build up in the as well. Most parts stores have inexpensive vacuum/pressure combo gauges that actually work pretty good.
It sounds like the last real work on the fuel system was 14 years ago. It may be a great time to check all of the fuel lines from the tank up to the carburetor and replace any rubber lines. An old collapsed line will also give you fits.