My 1962 554 has a gas gauge that malfunctions (I think it is the sending unit so will check that out), but also another problem I need help with.

It runs out of fuel, but a full fill will only put in about 5 gallons. I thought the tank held 8 gallons!

The tank was rebuilt about 3 years ago (before I got the car but I have a receipt from the shop who did the work - not local).

Is it possible the pick up doesn't extend all the way down? How do I check that out and correct it!


Thanks,

tom

If, as I suspect, the problem is in the pickup tube, don't be fooled if you see a tube that extends nearly to the bottom of the tank, as you might with a flashlight, or a flashlight and a mirror. Mine looked whole, but when I unsoldered it and pulled it out, it had a largish pinhole corroded into it that was invisible from the sender mounting hole. BTW, I cut the tube at that point and soldered on a piece of copper refrigeration tubing.
Bob S.

Hi Tom -

You've described my 444 perfectly.

In order to rule out the 'damaged pickup tube' theory on mine, I connected the fuel line to the fitting normally occupied by the drain plug, on the bottom of the tank. Poured 1/2 gallon into the tank, then went to the gas station, and it still only took 5 gallons.

Part of the problem, for me, is that Oregon doesn't allow self serve fuel stations. The law requires us to allow teenage punks unfamiliar with cars old enough to predate the narrow unleaded nozzles to slosh raw fuel all over the side of the car. Very nice.

I later found that I could squeeze 8 gallons into the car, but that it had to be dispensed v e r y slowly. Slower than the slowest rate that a filling tank pump will dispense.

Finally, I found that the burp tube (or whatever it's called) was almost completely blocked, preventing the air in the tank from escaping and causing an air bubble in the top half of the tank; which then prevented the fuel from entering at a reasonable rate. After reaming out this tube and finding spider eggs, rusty scale, old undercoating and other creepy stuff, the car will now take 8 gallons at the filling station.

Dunno if this is related to your issue, but it sounded familiar.

Best,

Cameron
Rose City

I have a 64 544 and just completed a new instrument panel, so I have a sending unit that I don't need. You can have it for the postage if you want it. My book shows the tank holds a tad over 9 gallons.

I would be very willing to pay postage for your sending unit if it works! I am sure part of my problem is a bad sending unit.

Contact me with your location and cost to mail to me, and I will send you a check.

Tom Mason
13158 S New Era Rd
Oregon City, OR 97045


tmason@coho.net

Thanks!!

If 1949 Bluegrass does not need your sender, I will be happy to have it!
Pete.

When the 544 runs out of fuel:
1. Take the fuel port (Mercedes lingo) cap off and shake the car and listen for sloshing of the three gallons.
2. Remove the sending unit and using a Model T gas gauge (stick) check the gas level.
3. Use an explosion proof light (not a match or electric bulb that get's dropped) a flashlight would be good, and look inside tank.

Right now my tank is out because the poor thing sat so long that the glue that was used to fasten the fitting that holds the pick-up tube came undone. Who would of thought they used glue, I haven't in my 25 years. My plan is to solder it back on. I flooded the removed tank with enough water to make me believe all the gas is gone. Most people would take it to a radiator shop for soldering, but I worry they might have a new guy who might put the thing in wrong and I would only be able to run out the first five gallons. Keith P.
PS. Although the gas gage is pretty hardy, I would handle like it is an expensive part.

Unless the tank is visibly smashed in on the bottom, then the pick-up tube is almost certainly the culprit. The only way to see it is to remove the gauge sender and peer in with a flashlight. Be careful, gas fumes are dangerous in many ways.
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I'm JohnMc, and I approved this message.

I see three possible problems with the rebuild: Either the pickup tube doesn't extend the bottom of the tank, the filler tube was set into the tank too deeply (so the gas can't be filled above the end of the filler tube inside the tank,) or your gas gauge is out of calibration, and you're filling up the tank when it's only a little more than half empty.

The place to begin would be to remove the gas gauge sending unit from the tank.

You can determine if the sending unit is out of calibration by measuring the depth of the tank through the gauge hole. The sending unit arm should drop only to a point about 1/2" less than the depth of the tank. That should leave you with a small safety reserve when your gauge reads EMPTY.

If the gauge flops around like the current is being interrupted, it is probably the windings on the sending unit. You can use some fine wet-or-dry sandpaper to carefully clean any buildup off the windings.

I actually had to take my sending unit apart to fix it, but hopefully you won't need to go that far.

If you don't find a problem with the sending unit, use a flashlight - preferably after dark - to try to see the ends of the pickup and filler tubes.

If there's a problem with those, you're on your own!