Fuel tank sending unit

[slpro1207]

Sorry for posting such a silly question but want to make sure I have no missed something. My fuel tank sending unit is the last item to be wired and plugged in. When I tested it by turning the ignition switch on, the gauge needle went right to empty and right back to full. Of course the tank is empty, and all of my other components, lights, turn signals, heater, wipers etc work perfectly. Is this normal? The wiring harness is the one supplied with the complete kit.
I don't want to lay in the trunk floor if there is a problem. Any advise would be welcome.

[edwardb]

This response may only apply to Speedhut gauges. They're the only ones I've installed so can only comment on those specifically.

(1) It's not unusual for the gauge needles to swing up and down on power up. So that alone isn't cause for concern. But they should stop swinging at the proper spot. You didn't say specifically, but I'm assuming the tank is empty. (2) Have you checked the calibration of the fuel gauge? The Speedhut instructions show how to do this. It's an easy step. Maybe that's all that's wrong.

[slpro1207]

Hi EdwardB. My gauges are the FFR GPS that came with complete kit. I have tried to calibrate both of the ways the instruction sheet shows but still back to the same issue. There has never had fuel in the tank. Could that possibly be the issue? I'm about 3 weeks away from engine install and first startup. I will be adding gas then.

[Jeff Kleiner]

The Speedhuts swing through full range when initially powered up so that's why you're seeing the needle sweep. Needle pegged on full can indicate an open on the sender circuit---start by checking your connections. The sender range is 16 ohms empty and 158 ohms full. If you check the resistance across the two wires you should see ~16 ohms with a dry tank (regardless of whether the gauge has been calibrated).

Jeff

[slpro1207]

Thanks Jeff. I'm getting 16.2 ohms on the meter. I'll start tracking a break in the line or bad connection.

[slpro1207]

Further testing shows 16.2 ohms out of the tank and 15.9 directly into the gauge. I will try to recalibrate again tomorrow. Thanks for the information. At least I know I don't have a break in the line.