Fuel gauge, sending unit, and tank compatibility

Hi All,

It appears my project has a newer (1970s internally-lit) fuel gauge and the older (screw-mounted) fuel sending unit and they are incompatible. Oops. Will my fuel tank accept the newer (locking ring) style fuel sending unit? If not, this means the fuel gauge, sending unit, and tank must all be from the same era?

Thanks!

Mark

Mark our resident guru from the Carolina's will be along to comment I'm sue but IIRC there are 3 different sending units / gauge combinations. In one gauge Full = 280 or something Ohms and empty.
0 Ohms resistance. Another one readings were reversed. You do need to have them match. I think there is a Wiki or search on gas gauge and you can find it.

I haven't seen Kim (a.k.a. Regularman) post in a while. You may want to send him a PM so he can clarify the points Jim mentions above.

Until you hear from him I can at least confirm that you are correct in your assumptions that you cannot mix the gauge system components that operate without the voltage stabilizer with those that do. As Jim pointed out, the sending unit resistance range is different and the resistance changes in different directions as the tank is filled.

Thanks for the replies. I've surrendered to the fact that the fuel gauge components must be electrically the same. Will a locking-ring style fuel sending unit mechanically mount in an older screw-mount style fuel tank? I've read 50 threads mentioning fuel gauges and stabilizers but this mechanical aspect has never been mentioned.

The locking ring version will not fit directly. You can make a retainer ring with a hole pattern to match the tank. I've done this on one of my cars.

The early sprites used a 2530/31 Smith gauge.....the sending unit reads approximately 0 to 90 ohms. 0 ohms for an empty tank and 90 ohms for a full tank. The later sprites used units which operate in the opposite configuration. Scott in CA

You may want to consider changing tanks if yours is the least suspect since the later tank's increased fuel capacity. A friends motorcycle has more fuel capacity than my spridget's. Course I get as good or better mileage!

Kurt.

In the spirit of practicality, I would like to find an original FG2530 fuel gauge that will work with my original tank and sender (I have a '62 Midget Mk1). It appears the MGA used an FG2530/05, the MGB used either the FG2530/63 or FG2530/70, and Triumphs used the FG2530/20. Can these different dash numbers be interchanged? I'm only worried about functionality, not whether it says Smiths or Jaeger, or if the glass or chrome bezel were a little different (I already have these to match my existing gauges). Thanks!

The early gauges without the stabilizer can be calibrated to match your early sending unit regardless of what the original application is/was.

Visit Barney Gaylord's MGA-Guru web site and read through his fuel gauge articles. He both explains how the early gauges work and how to calibrate them. Start with the link below and read through the subsequent pages for all the details on the early fuel gauge. You do not have to build his calibration box nor do you need to buy calibration resistors. Simply use your existing sending unit (out of the tank if possible) so you get your gauge calibrated to match your sending unit. Pay attention to where the wires connect to the gauge and make sure both the gauge and sending unit have good ground connections. That is imperative for the early gauges to work correctly.
https://mgaguru.com/mgtech/electric/fg_01.htm

I moved the electromagnets in the fuel gauge on my Mark I Mini (which is part of the entire instrument pod). Very similar mechanism (though mine didn't have the resistor). It doesn't take much of a tweak to affect the sweep of the needle (and I'd eliminated all other issues). One does need to be very careful with those delicate wires (and avoid them altogether). It came out great.