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MG TD TF 1500 - Why is the fuel sender open to the fuel?

Why is the fuel sender designed to be open to the fuel?

Just curious. Today, wondering if the fuel sender might leak, I filled it with gas and sure enough, it leaked very slowly around the arm where it exited the sender. That appears to be the only entry point for the fuel.
So it is open, and will very slowly fill with fuel. But when the tank is low, it will slowly drain; and given enough time with an empty or low tank, the level of fuel in the sender will lower or evaporate entirely. At which point you have an air gas mixture in an a box, with an open spark occurring whenever the connection is made to the battery and the arm is in operation. Isn't that a bit dangerous?
From a safety point of view, should you fill the sender with fuel when installing, so that there is less of a chance of having much air in there?
Geoffrey M Baker

Wondering why ? It's made in Britain but it works .
Don't worry about it they all fill up with fuel and I have never learned that the fuel tank explodes due to the design.
Gerard Hengeveld

It's open because the alternative is sealing the pivots, which is not likely to be successful.

As for causing an explosion--look at the location of the contact and the position of the unit when it's in place. The contacts will always be submerged--they are below the level of the pivot, and the fuel below that level can't drain back into the tank. Even if there were a spark in the volume above the fuel, there wouldn't be enough air to sustain a fire.

I think it's obvious that, if cars were exploding because of the fuel-level sensor, we'd all know about it. So, it's one of those things you can convince yourself is a potential problem, but in real life it just doesn't happen.


S Maas

Its also safer.

Fuel need oxygen to explode.
If the sender is totally immersed in fuel there can be no explosion.
If you tried to seal it and had a leak it would, potentially be dangerous.

Jim B.
JA Benjamin

The electrical contact sits in an environment where the fuel and fuel vapours are well above the H.E.L. (High Explosive Limit) of gasoline. And always will be, unless the tank is totally drained and fully vented.

So if you ever remove the tank for cleaning or service, disconnect the sender.

...CR
C.R. Tyrell

CR, that's the conclusion I was coming to, that the only real danger would be an empty or near-empty tank sitting for a long time allowing the gas in the sender to vaporize. I won't worry about it; but as a safety precaution I think it might be a good idea to fill the sender with gas when reinstalling, leave it disconnected, and immediately fill the tank with gas.
Geoffrey M Baker

Geoff, You have no worries. When you re-install the tank, by the time you have 3 gals. of fuel in the tank and the connection breaks (light turns off) the HEL will be well exceeded. Or just if you will feel safer, connect the sender unit wire after you have some gas in the tank.

..CR
C.R. Tyrell

You should watch myth busters. It is virtually impossible to get a fuel tank to explode...despite what Hollywood tries to sell us. On their fuel tank explosion episode they just could not MAKE it happen..open flame, explosions, etc. no induced fire. Regards, Tom
tm peterson

Oh cmon Tom. We all know that if you shoot at any moving vehicle with anything larger than a cap gun, it will immediately fly into the air, turn over twice, and explode like it was filled with C4.
I am also pretty sure we never landed on the moon and that Obama was born in Kenya.
Geoffrey M Baker

This thread was discussed between 06/12/2014 and 08/12/2014

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