Low fuel light with full tank

Hi, I had cause to remove my tank and fuel pump unit from a Commando (long story, for another thread).

I put it all back together, bike runs great but now the fuel light is permanently on even though the tank is full.

I presume it’s some sort of switch inside the pump assembly that ‘completes’ when fuel drains low, or maybe a mini float.

I don’t really want to take it all apart again if I don’t have to.....

Anyone know how the switch works and whether this is something likely to fix itself ?

Thanks Rich

These are from Richard-7 manuals showing the location of the low fuel switch inside the pump assy.

Give the pump a few raps on the bottom , (be careful not to break the spigot). Also make sure that the relay is not faulty.

Thanks Tony - I’ll give it a go (I’ve got a small hard-plastic hammer that should work). I’m hoping it’s just sticking somehow...

Fixed ! After going for a sunny ride to empty some fuel from the full tank I stripped it down again. The sender is the small cylinder shown in Tony’s picture above. It has wires top & bottom and small holes to allow fuel to rise and fall in the cylinder. I assume the fuel completes a tiny circuit and when the level drops, circuit is broken and light comes on.

When refitting the pump unit back through the tight aperture in the tank base, looks like I accidentally squeezed the cylinder and hence one of the wires against the large metal fuel filter. This was enough to disrupt the tiny circuit and illuminate the light.

Slight tweak and all sorted. Hopefully no one else has this problem but when we all eventually upgrade our plastic tanks for ally, one to watch out for !

Rich

Good One !

Thanks again to Richard and David Coote for their work on these very helpful manuals ! Now let's get some miles under our belts.