1950 DeSoto fuel pickup problem

[Ancient Jon]

Does anyone know what the fuel pickup inside the tank looks like? My DeSoto runs out of fuel a little under 1/2 tank. I'm wondering if the pickup is broken or has a hole in it. 

[Don Coatney]

Is your fuel gauge working and accurate? 

[Ancient Jon]

It seems fairly accurate. The most I have ever put in it was 8 gallons.

[keithb7]

Here is my pick up screen flopping about after it became unsecured from the tank floor. 1953 Chrysler.

 

[Ancient Jon]

I'm wondering if mine came loose and moved up off the bottom. I added 5 gallons to it and its now reading almost 3/4 of a tank. The gauge worked fine with the sender out of the tank. 

[_shel_ny]

This is a long shot, and could be off base, but try putting some dry gas in there.

 

Not sure why it would not happen all the time if it were the problem, but if there is water in the tank it will not pass through the fuel tank pickup filter.  Water will block the passage of fuel until it is disturbed, and moved away from the filter.

 

 

[FlashBuddy]

Dry gas? New one on me. 

 

Found it on Amazon ? Cheap too.

Edited May 14, 2018 by FlashBuddy

[dpollo]

I suspect the fuel line is leaking air at the fitting where the line leaves the tank.  This is not an inverted flare fitting like most people think.  Up to 48 there was a little ferrule which made the connection airtight within the tank and leak proof to the outside.  From 49 up the fitting at the end of the line is kind of bulb shaped and the "nut" is extended past its threads so it will go in far enough to contact the dip tube.

[Dodgeb4ya]

A picture of this fuel line into the tank fitting 1949-50 all Mopar cars...

[Ancient Jon]

"Ran out" of gas again. 11 gallons filled it up. So there is roughly 6 gallons in the tank when it goes empty. I'm thinking the entire fuel pickup has come loose inside the tank.

[busycoupe]

Check the fuel line, especially where it goes over the rear axle arch.  If there is a pinhole leak there the car will run as long as the level of fuel in the tank is above the pinhole. But when the fuel level is low the fuel pump sucks air through the pinhole and won’t pump gas.  

[keithb7]

1 hour ago, Ancient Jon said:

"Ran out" of gas again. 11 gallons filled it up. So there is roughly 6 gallons in the tank when it goes empty. I'm thinking the entire fuel pickup has come loose inside the tank.

 

I sure am interested in what fixes this. I have had similar instances where I show gas in the tank, but ran out. Fixing the fuel pick up tube flopping around in my tank, I thought solved my problem too. Until 2 weeks ago when I again ran out of fuel with a 1/4 reading on the fuel gauge. 

 

I have yet to fill the tank right up and see how much it takes. My fuel cap rubber seal is old and dry. Sloshing fuel will leak out if my tank is over 3/4 full. A new fuel cap is on the way now. Soon enough I will fill mine up and see.

 

@busycoupe, if there were a pin-hole in the fuel line where it goes over the axle arch, would if not drip fuel when left sitting parked? This is new and interesting info.

Edited May 23, 2018 by keithb7

[Jocko_51_B3B]

Here's what a fuel sending unit looks like inside. This post also shows why they can have problems...

 

 

[busycoupe]

My car had pinholes in the gas line over the arch.  It would run fine, but when it sat with less than half a tank of gas the gas would drain from the high point in the line and then the pump would suck air and not pump the gas. I had to pour gas into the carb to start it.  Don Coatney told me to look for a leak in the line and when I pulled the rear wheel I could see that the line had been seeping gas, not enough to make a puddle. I replaced the entire line and in the process found a couple of more pinhole leaks that were buried in grease and gunk where the gas line goes under the front of the engine to the pump.  Since replacing the line I have had no starting problems.  Check the rubber line connecting to the pump also.

[keithb7]

Does one cut and bend their own gas line, similar to a brake line? Except that end as shown at the tank fitting seems odd. I've never replaced one of these old gas lines. I am wondering where one may source the gas line. Thanks.

[busycoupe]

I used lengths of bendable gas/brake line from the auto parts store.