The Official 356Talk Forum

ok

Guys

So here is the skinny
my tank is drained for the winter . so i was able to remove the sending unit my original gauge connected cap tube is literally 1/3 of an inch above the pump connected tube all tubes are clean as a whistle. It holds a reading in a gallon can until i slosh it around and the bell looses air to
the sloshing .
I cut the 1/4 inch tube and shortened the gauge connected capillary tube to half the length of the 1/4 support bell tube .. soldered everything back together .

it works perfect holds a reading with vagarious sloshing around ..

learned something new .. The gauge connected cap tube position needs to be fairly far inside the 1/4 tube to avoid loosing the fuel level on the gauge it makes perfect sense .

its actually quite disturbing from what i recall. all the units i have worked on the gauge connected cap tube line was always very close to the pump connected cap tube ...

Allan thanks for the knowledge

Regards Ned

Love this thread! =)

James, we pre-A guys have to stick together! Probably no one else cares about some of this pre-A minutia, although I was kinda waiting for a comment from Cliff along the lines of "it is really inaccurate...reads 12 gallons in a one gallon bottle!"

Ned,

Here are the fotos of the parts I m searching for
Tom

Going through some old papers and found the operating instructions for the Beck gas guage.

X2 Love this thread.

Found a fuel gauge with tubes and button, sat in a box for 20 years till a couple weeks ago.
Didn't know anything about it till I just read this thread.

N Hollywood Speedo said my tank diaphragm is missing. They said they convert them to electric with a later sender.

I took my gauges home and didn't have them fix them. $$$

I'll post a pic in a while, raining hard now in So Cal.

Hello,

Attached picture shows the parts of the fuel gauge pump of my MY53 project. I think I understand the function described in this thread, and I am currently searching for a source for a new rubber piece.
What puzzles me is how the air between the plunger and the rubber piece is exchanged. There is the small hole which is supposed to be closed with the finger when pumping. So, where is the compressed air going when the hole is closed and the plunger is depressed? On my parts I don’t see anything allowing the air to flow between the plunger and the inner of the rubber piece.

Was there something clogged on the plunger during the chroming process by a PO or do I miss an additional part?

Martin

Martin
The path of least resistance, The air is forced out or the rubber pump billows into the capillary tube. Then the air is captured by the brass inverted cup in the tank.,as the air fills the inverted cup the pressure inside the other capillary tube builds and registers on the gauge. the higher the fuel level the higher the pressure . It is very common for the cap tubes to be clogged as well as the brass check valve piece of the back of the pump housing .. you can soak in acetone to free them up.

Regards Ned
55 cab

Thank you Ned, for your explanations!
I will try to get the clogged check valve back to life with chemistry. With a valve in the back part of the pump housing, this part must be divided into 2 pieces? Does someone have experience and instructions on how to open it?
Great, so now I understand how the air is getting out of the rubber pump (the destroyed redish balloon on my picture – in Tom’s picture it has kind of a greyblue color) to the tank - and not returning from there .
Still, I do not understand how the ‘fresh air’ (as mentioned in the Beck operating instructions posted by Alan) is getting inside the rubber balloon. I am missing a kind of connection between the plunger and the balloon. Up to now, I thought the check valve function for getting the air in and compressing it is the finger motion.
Any other thoughts on this?
Martin

Martin,
I have never had one of these pumps apart but I would guess that the rubber pump piece goes over the collar at the rear of the plunger and I suppose the hole goes all the way through the plunger such that when your finger is off the plunger, air goes through the plunger and into the center portion of the pump rubber piece, then when you cover the hole and push the plunger the air in the pump rubber is compressed and goes out the back of the pump, through the check valve and into the capillary lines. When you take your finger off the plunger the rubber pump piece returns to its normal shape and refills with air though the plunger hole. Couple of questions, how does the hole on the plunger go through the plunger? and it looks like the circular center piece on the rear piece of the pump is the check valve, but in your case it appears to have a hole through it, is this the case and does it look like it might be broken out or does it look like it was made that way? I can see where the small "nipple" at the rear of the plunger might have been used to push the check valve open originally and with use has punched the hole in the check valve, which would make the pump non operational. Maybe more pictures might help in understanding how the pump is intended to operate.

Earlier versions of the BECK gauge used a smaller pump with, I believe, a diaphragm rather than the barrel shaper pump rubber. The change in the pump was probably made to move more air per pump stroke so fewer pump strokes would be required to correct the reading. I found a photo of the earlier pump on what I assume is a VW application.

Hi Alan,
Thank you very much for your descriptions and your confirmation of another hole on the plunger rear side.
With all this information, I will do 2 things: Try to get the check valve on the brass piece to work and get rid of the chrome on the rear end of the plunger in order to - hopefully – find some kind of hole there.
I will report back with the results in approx. 3 weeks.
Martin

the main secret is: you need a play between the pump rod and the rubber ball hole.
Just less than half a mm.
When you release the rod, the air goes into the ball by this slot - and not by the hole in the rod.
And the very tiny valve at the housings cover is opened by the pointy end of the rod and closes immediately when you release the rod.
We sell new balls.
www.classic-parts.fr
Albert

As always, it took longer than expected, but finally, here are the results on my hand pump inspection:

The plunger has no opening at the bottom end – at least my example does not. This confirms Alberts statement, Thank you!
What remains as a mystery to me is the hole in the plunger top and the Porsche instructions how to open and close it during activation….

The brass bottom of the pump housing has a valve with a spring loaded ball and a rubber seal. The round brass cover is just calked in the bottom brass piece. As shown in the picture, my valve rubber seal is toast. After making a new one and after getting a new rubber balloon, I hope to get this little pump back to work.

Martin

I would like to add a fuel gauge to my 55 speedster.

what are folks using to achieve this?

Just to close the previous topic, here is a picture of the finished hand pump. The bottom valve got a new seal cut out of 1mm thick gaz resistant(!) rubber with a 2mm hole in the center. The rubber balloon was purchased from Albert Häfner and glued to the brass base. The housing holds the rubber balloon in place. The first trial run of the pump went well. Martin