>
> We're about to replace the fuel tank sending unit on our MGB. We are
> sure that the existing one is bad.
>
> In light of the fairly recent discussion about explosions and gas tank
> modifications, does anyone have any suggestions/precautions about how
> the replacement should be done?
>
> I think the current unit leaks a little when the tank is full. Is
> there a sealant we could use to leak-proof the new sending unit?
>
> Thank you,
> Lydia Gregoret
>
> P.S. About ready to sell the Honda and rely on the MG full time!
You'll be sorry :-)
>
>
I sorta replaced the fuel tank sending unit in my 69 MGB about 2 years
ago. What I actually did was to take it all apart and wind up putting
the old one back in. Anyway the story goes as follows. When I bought
the car, the fuel gauge did not work. The first thing I did was to take
the gauge itself out of the dash and test in on my workbench. With a
12 volt power supply and the right resistor I could make it read any
value I wanted, so I knew the gauge was good. One point of interest,
reading approx. half full, the gauge would draw over an amp of current!
Leave it to Smiths to make a fuel gauge that wants 15 watts of power
just to give you a reading. Anyways, next I put my resistor on the
end of the wires that normally go to the sending unit. Again the gauge
would read according to the resistor used, so I knew the wiring on the
car was good. Ok, so I send for a sending unit. This part sat arround
for a while, until one day I noticed a leak in my fuel tank. The
easy way to drain the tank is to unhook the fuel line to the carb. and
use the fuel pump to pump the gas into a gas can. I didn't know how
much gas was in the thing when I noticed the leak, but it turned out
to be about 6 gallons requiring that I run off to an auto store and
quickly buy a 5 gallon gas can to go with the 1 gallon can I allready
had. Anyway, I pulled the tank out and took it to a radiator repair
place and they fixed the leak. When I got it back, I was all set to
put in the new sending unit, but then I got to looking at this new
sending unit. There is a sliding contact along the side of what is
basically a wirewound resistor. On the orginal, this is inside a small
metal box which, when emersed in water, no bubbles come out, so I
summise that no liquid gets in. On the replacement part, you can
see the contact point between the resistor and the arm attached to
the float. Knowing that more than an amp of current is going to
be going thru that contact point made me say "Wait a minute. If this
thing breaks contact and sparks while the tank is near empty, there
is going to be a big BOOM!" I don't know if this would ever actually
happen or not, but I'm not going to find out by experiment either!
I put the old sending unit back in and to this day rely on other means
to know when to fill the tank. First is the trip odometer, the second
is an early warning from the after-market fuel pump that will start
rattling like the dickens when it's not getting any fuel from the tank.
My advice to others is not to buy the sending unit from Victoria British
Ltd. like I did, and second, if the sending unit is not sealed in a box
like the orginal, then don't buy it. Replacing the unit is not difficult.
First drain the tank. The sending unit is held in place with a lock ring
that rotates to release the unit. Mine came out with no problems. If
the lock ring is stuck and tapping on it with something seems necessary,
I would recommend that NOT use anything metal. A wood block should do
the job. If you still have trouble, consider taking the car to someone
else and let them do the pounding while you're a long ways away. Be
careful once the old sending unit is taken out. Any sparks or flame at
this point could ruin everything. Also do this in a well ventilated
area. I forget if there is a seal on this or not, check the Moss catalog,
if they sell one then there is one. Any sealant that can resist gasoline
can be used to seal any leaks.
--
Andy Haber (andyh@HWD.csd.harris.com)
Harris Computer Systems Division, Ft Lauderdale, FL
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