After owning my 1980 Spit for about 12 years, I finally have a fuel
guage that shows the right fuel level. Maybe many of you know already
that the unit can be adjusted, but I didn't see the fix among the
maintenance tips on the VTR web site, and I just discovered how to do
it a few days ago.
Since I bought the car, the fuel guage has read just a little beyond
half full after a fill-up. Recently I pulled the sending unit from the
tank (after disconnecting the battery!) and discovered that the float
had some fuel in it. After draining the float and sealing it (with
the advice of some list members) I thought everything would be fixed,
but the guage still showed only about two thirds of a tank when I knew
it was full. By the way, I knew the guage COULD show the full range
because shorting the two sender leads together produced full needle
deflection.
Though my Haynes manual claims that the unit is unserviceable, I
decided to fool around with it because I had another sender off a parts
car. I pried up the three metal tabs holding the cover on and exposed
the wire-wound resistor. The cover didn't come up all the way because
of the electrical connectors between it and the spade connectors on the
outside of the cap that fits in the tank opening. But I could see that
the metal pointer that slides along the resistor didn't actually go all
that close to the low resistance lead when the moveable arm holding the
float was pushed all the way up (as if in a full tank). I could also
see that the metal pointer pivots on a fiber post that protrudes
through the cover when the cover is closed. This extension of the fiber
post has a slot so that a screwdriver can be used to turn it slightly.
Doing so affects the position of the pointer on the resistor and changes
the guage reading. The neat thing is that the adjustment can be made
without prying open the cover to the resistor. However, in my case I
would have had to open it up anyway. When I turned the post, the
resistor suddenly had infinite resistance; there was a break in the
connection somewhere. It turned out that I simply had to shine up the
spring which surrounds the fiber post and makes an electrical connection
between the cover (with a spade connector) and the resistor. When I
did this and pushed the cover back in place, I could change the resistance
slightly by turning the slotted post. I adjusted it for the lowest
resistance when the moveable arm was raised to its highest. Then I
put the sender back into the tank (battery still disconnected) and went
to the gas statiion for a fill-up. I was very happy to see that the guage
went up to "full" for the first time since I have owned the car. All in
all, this was a pretty easy job.
Tim Gaines
1980 Spitfire
1976 TR6
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