So today I be mostly attempting, yet again to solve my faulty fuel gauge reading problems. When I bought the car the gauge was pegged at just under a 1/4 no matter what amount of fuel was in the tank. I bought a new sending unit, the one already installed was incorrect for the car anyway having no inlet pipe for the vapour return line, which '66 Wildcats equipped with A/C have. After installing the new sender the gauge read empty, all the time I checked the gauge when I had the dash apart and all seems fine. When I pulled the wire from the sending unit to the gauge the gauge pegged to full, when I grounded the wire the gauge pegged to empty... as it should. I ran the car to empty the tank a little as it was nearly full and pulled the sending unit out. I checked the sender with a multimeter and the ohm readings are correct when I move the float up and down. 2.1 @ empty & 98.7 @ full. I then hooked both senders up to the gauge in turn, they both seem to work correctly but when I checked the dash gauge the pointer moved but only read just over 1/4 when the floats were in full postion and around halfway between empty and 1/4 on the gauge when the float is in half full position. When I installed the sender back in the tank and wire it up I get no reading at all from the fuel gauge again. This has me wanting to scream.... God, I hate messing with vehicle electrics. So does anyone have any suggestions at all? I've searched so many forums and one thing keeps popping up with this scenario... resistor fault. But that doesn't explain the reason why I get no reading at all when the sender is installed in the tank. I do have a good ground for the sender unit, that's for sure. The incorrect sender unit with no vapor return inlet which was in the car when I got it. The correct sender in place but with blocked off vapor return inlet which someone installed for me. Gauge reading when float is at full position. Gauge reading when sender float is at half way position.
From my 1965 Buick Sklylark Chassis manual, it agrees with 72STAGE1's response (dash unit reads "empty" or noticeably low at all times, look for a ground in the wiring circuit between the dash unit and the tank unit connector).
After more tinkering I manged to get the fuel gauge to read correct when hooked up to the sending unit out of the tank. On the back of the fuel gauge is a strip wound with wire, after closer inspection with my dodgy eyes I noticed a break in the wire. And here it is back in situ after repair. The gauge now gives the correct fuel level reading when I move the sending unit float up and down. All have to do now is figure out why the fuel gauge does not work when I have the sending unit installed in the tank, I know there is good ground to the sender because it works when out of the tank and it is connected using the original car wiring.
Well, that is interesting. Glad the gauge issue is resolved on the dash side. I've often wondered if we could substitute an appropriate resistor in place of the wire? On the tank sid, I would take a small container and sit the sender in it and fill it with water to see if the float does indeed float. Water is heavier and safer than gas so you can observe the gauged action as the bucket fills. Once you know it isn't defective with water, you can try it with gasoline enough to make sure it still floats in a lighter liquid.
The tan wire from the sender to the gauge is ground, it must have good continuity from the gauge to the sending unit to include any interim connection points. Since you have been able to get this far, you know where and how to make the connections. run a temp wire from the gauge to the sender post and see if it remedy's your issue. If so, you will either need to run the wire under the sill plate or pull the seat and either address the connections along the way or run a separate wire. Most of the time, there is the pigtail at the tank, and that has a connection to a wire that runs to the rear connector of the flat ribbon, floor (body) harness, and then to the front of that harness to the connector and that connects to the bottom of the fuse block, then is pinned to a wire that runs up to the back of the printed circuit board that the gauge mates with to complete the connection. Hope that helps. (there are some variations to that sending wire run on different models/years)
Thanks for the pointer. Apologies but I guess I could have been clearer in my description. I know the tan wire is not grounding because I had the sender out of the tank but used the original tan wire to complete the circuit. My car is a '66 and you don't need to drop the tank to get the sender out. I just supported the sender under the car, out of the tank but connected to the car's existing tan wire with the sender grounded to the same area where it will be when in the tank... sorry if this doesn't make sense.
OK. In case I misunderstood what I have read. (olde folk do that...) So I re-read. With your gauge, now fixed, and installed, and the tan wire with sender connected and grounded and out of the tank, the gauge the swing of the needle to the range of the float arm os correct? But with the sender in the tank, what is the reading from lowest to highest (and how are you articulating the arm with the sender in the tank)?
Do you have a grounding wire coming from your sending unit back to your car's chassis behind the tank? I know you have a 66, I have a diagram for a 65. I would think they would be similar, if not the same. See the attached
[QUOTE="TrunkMonkey, post: But with the sender in the tank, what is the reading from lowest to highest (and how are you articulating the arm with the sender in the tank)?[/QUOTE] I have around ½ tank of fuel but the gauge needle stays on empty.
Can you measure from the lip of the tank hanger flange to the fuel level, then hold the sender so that the top is horizontal to the ground and measure where the float hangs? (about the center of the float.) Then we can see if the float hanging is above, at or below the current fuel level. As I am wondering if the new sender is correct for the car.
Well, this mystery keeps deepening. Spent over 4 hours with the help of a call out mechanic trying to get to the bottom of things, when, finally one of us had the good idea to look into the hole which the sender sits in. We saw either a strengthening brace or baffle to stop fuel sloshing around too much I guess, please correct me if I'm wrong. Due to the length of the sender this is in the way of the float operating correctly and also, we assume causing the sender to ground out but it's very difficult to tell when you can't see what's going on inside with the sender in place. This is the sender length, and is correct for my '66 Wildcat. (disregard the jubilee clip, this is the old one we played around with, without the vapour return line for AC cars) My thoughts would be that the tank is not correct but it looks exactly like the service manual diagram for my car. I forgot to take photos of the tank when we dropped it but I have some of it in situ. Also a picture of the vent outlets as per diagram. So what do you think, is the tank wrong for this car?
