How can we check/test the Fuel Gauge?

Camel, Sahara, Kanguro, Coguaro
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julianharty
Posts: 478
Joined: 15 May 2016 16:34
Location: High Wycombe
Location: High Wycombe Area (Bucks)

How can we check/test the Fuel Gauge?

Post by julianharty »

My X3 came with some wires emerging from the left, manual fuel tap. I understand it's intended to provide some sort of indicator of the fuel level. I don't know what, mainly as my bike has a custom instrument console that replaces all the idiot lights as well as the speedo and rev counter. My guess is that it's intended to indicate when the fuel tank is nearly empty. I'd like to (a) see if it works and, if so (b) wire it in to my fancy instrument console which has a spare light. What I don't know is what the reading(s) are meant to be from the circuit in the tank. Can anyone enlighten me please?

Currently my tank is nearly full and the circuit seems to be an open-circuit. Of course I can measure again once I've ridden the bike enough to use most of the fuel (about 250+km I'm guessing). Given the propensity for this bike to have a new fault after roughly 60 miles / 100km or less that might take me a while to reach... BTW: Here's hoping that replacing the regulator/rectifier is the last of the gremlins on this bike :)
MickeyMoto
Posts: 2415
Joined: 22 Nov 2008 17:41
Location: Even further oop North

Re: How can we check/test the Fuel Gauge?

Post by MickeyMoto »

Hi Julian,

The Excalibur has the same thing (and the Dart?). I think the fuel light may be a reed relay. There is what looks like a magnet that rises and lowers dependant on fuel level.

I put mine on the Strada where the electric tap used to sit. I use the reserve tap position with a standard tap, but the light comes on after it goes onto reserve. I really need to be brave and take it further on reserve to see when the light comes on. I only get 9 litres in when reserve kicks in. Some fettling to do.

To test, try leaning the bike away from the tap side and measuring the resistance. If tank is low should go from open circuit to fsd when the 'magnet' lowers. It is a simple device and also very reliable.
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