Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Fuel Gauge, Wow and Thank you

Took the Morgan out today, first proper drive ever and wow - it felt amazing, I've been waiting for this moment since I first found the car in the barn back in March last year. I wanted to thank everyone who has given me the advice and confidence to get the car to this far - without your help I wouldn't have known where to start.

Taking it to get fuel for the first time it's clear that the fuel gauge isn't working, it hovers at the 1/4 full mark the whole time and I was wondering if somebody could give some pointers as to the logical steps to isolate the issue or where I should look t get replacement parts.

Thank you all again, I hope I can be a net contributor to the site at some point

Great news!

I'd start with the sender in the tank - take the wire off it. Check you have power coming from it.

Then earth the wire - that should move the gauge needle.

If you have power, and the gauge works, then it's the sender.

You can also check the continuity of the wire from the gauge to the sender, and also check the voltage of the wire going to the sender. It should be around 10V, not 12V. There is a voltage stabilizer that provides the feed to the temp gauge and fuel gauge. Is the temp gauge working OK?

Here's the wiring:

I would also check the earth. Earths on mogs often fail.

I am sure MMC use special metals for the earth.
Probably from the group in the Periodic Table ....Rare Earths.
Apologies but I couldn’t resist ( no pun there either).

Very good!

+1

TBM's wiring diagram of the instrument voltage regulator reminds me of the need for same. Late 60's and into 70's and beyond, fuel and temperature gauges worked on the bi-metallic principle where an electrical current would heat such a strip of metal which would distort in a manner proportional to the voltage driving the current, so allowing mechanical linkage of strip to gauge pointer. It also gave very damped readings which was an advantage with fuel sloshing around tank. The technology only worked with a constant reference voltage though, which battery charge systems didn't allow, hence need for 10 volt regulator.

It can be seen if regulation fails an erroneous gauge reading will ensue.

Yep, replaced mine with a solid state regulator - gives me much more accurate temp and fuel readings. Regulator