At 09:12 PM 10/26/97 -0500, you wrote:
>I'm still working on VIN 1758....it runs great, but still has a few things
>that bug me...
>5. The fuel guage is not working. Every once in a while it will move from
>its home (empty) and go to the right place on the guage, say 1/2 tank. Bad
>connection, maybe, or is it a bad guage? Please dont say its the sensor in
>the tank. If i have to replace that, I had might as well go ahead and
>restore the whole car from the ground up.
>
Riley,
Here is a responce I sent to someone else with the same type of problem:
The fuel guage system has 2 parts, the guage and the sending unit. The
sending unit is mounted inside the gas tank.
If the guage moves at all, then the problem is probably in the sending
unit. To test the guage, you will have to jack up the rear of the car
(and support it on jack stands). Slide under the car. You will have to
slide you head forward past the gas tank so you can see up to find the
wires. You might also need an inspection mirror and some light to help
you see. On the top of the gas tank, you will see a wire that is connected
to a post on the sending unit. This wire is a "push" on connection and
can be lifted off the unit. This is also the "Hot" lead. Lift/pry it off
of the sending unit. Now have a helper turn the ignition to the "ON"
position and see if the guage moves. (Note: I'm not sure which way it will
go on this test, but it will either peg full scale or stay at empty). If
it goes full scale, test complete and the guage is fine. If it stays at
empty, you will have to perform a 2nd test.
For the 2nd test, you will need a piece of wire (any wire will do). Hold
one end of the wire to some metal part of the chassis. (Preferably a spot
that you clean with some sand paper until the metal is nice and shinny.)
Push the free end of the wire into the connector on the end of the wire
you removed from the sending unit. The meter should peg. If not, then
there is a problem with the meter or the supply voltage. (Troubleshooting
this is beyond the scope of this article.)
If the guage did move then, the problem is either with the sending unit
or its ground wire. The way most sending units work is there is a small
compartment on top of the sending unit that houses a variable resistor.
The wiper are that runs along the resistor goes to a pin (flucrum). On
the other side of the sending unit, there is a long arm that the float is
attached to. As the gas in the tank raises and falls, the float, moves up
and down causing the wiper arm to move from one end of the resistor to the
other.
Problems:
1. The ground wire from the sending unit to the chassis is not making
good connection. To check this, while you're under the car, look
up above the gas tank and slightly forward. There is a black wire
(the other wire) that come the sending unit and goes to the chassis.
It is attached by a small screw. Remove the screw and clean the
connector on the wire and the chassis metal with a piece of sand paper
until shinny. Reattach the ground wire to the chassis and the hot
lead to the sending unit. Try turning the ignition on again and
see if the guage works.
To check the remaining problems, it will require dropping the gas tank and
removing the sending unit!
The only way I know of to check it is to pull the sending unit out of
the tank. To do this, you will have to drop the tank. You'll have to
pull the main fuel line and vapor return line's flex hose off the tank and
there is a ground wire that goes from the tank to the chassis. Then there
are 2 nuts, one on each of the "J" bolts that hold the back of the gas tank
straps up. I put a jack under the tank and then loosen these nuts, once
the straps are free, the tank can be lowered and slid out from under the
car. (You'll have to have the car in the air on jack stands of course.)
To remove the sending unit, there is a "slip ring" that is sort of wavy
and catches on 3 or 4 ears. Carefully rotate the ring untill it disengages
from the seat on the tank. It may be necessary to hit the ring to get it
to rotate. To do this, place a wooden stick on one of the ears of the ring,
and hit the wooden stick with a hammer. BE VERRY CAREFULL!!! YOU DON'T
WANT ANY SPARKS AS YOU WILL HAVE GAS FUMES FLOATING AROUND!!!! Once the
ring has given, the sending unit can be pulled out and checked.
If you are going to go to this much trouble and haven't had you gas tank
cleaned and coated, it might be worth thinking about at this time. I sent
mine out to a radiator shop to have it boiled and lined with some sort of
rubber gunk. Hopefully, this will keep the tank from rusting out.
Remaining problems with the sending unit:
2. The float can collect junk and get too heavy to float, or it can get
a hole in it and not float. Sometimes these can be fixed by cleaning
the float and or patching the hole with epoxy.
3. The bare wire on the resistor or the wiper arm gets oxidized and so
it can't change the voltage. The cover over the resistor is usually
held inplace by 4 to 6 screws. Remove the cover and spray some TV
tuner cleaner on the resistor and wiper and move the float up and
down to clean the oxidation off.
4. The wire in the resistor breaks. You're Sh$% out of luck!! If you
are really into pain, you could try and find some resistive wire and
rewind the resistor and the scrap (sand) off the insulating coating
to allow the wiper to pick up the voltage.
In the long run, as long as they are available, that is probably better to
replace the sending unit. I purchased one for 887 for about $45 a couple
of years ago.
According to my info, the Gas Tank is AMC Part #4488034 from a 1974
Gremlin. I purchased a sending unit back in 93 from American Parts Depot.
The Part # is 812-5394 fuel sender @ $45. I believe that this is an
AMC part #.
John
John T. Blair WA4OHZ email: jblair@exis.net
Va. Beach, Va Phone: (757) 495-8229
48 TR1800 48 #4 Midget 65 Morgan 4/4 Series V
75 Bricklin SV1 77 Spitfire
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