Replacing the Fuel Gauge Sender Float

I've refitted the sender. it's the thing in the tank that tells you how much fuel you have left in the tank. the cork that makes up my float was cracked and I believed would become saturated and heavy if fitted as it was. So I fitted a new float.

The first thing to say....is that you can buy replacement modern fuel gauges with a modern, sealed float.

Modern reproduction fuel level sender for a DS

However I've read very mixed reviews of these. Some of which point to poor build quality and others that point to accuracy - though that could be as much to do with how they are set up when fitted. No. that wasn't for me. I intended to re-use my original jaeger-branded sender. I just had to find a suitable float.

I've seen some fuel gauges that were badly corroded - outside and in. I'd taken a look inside my Jaeger to make sure it didn't look like this.....

No. it looked to be in good condition. I gave the wound wire and moving contact arms a gentle clean. They are both quite delicate.

The float on the original jaegers is a rectangular box with a flat bottom. The arm hangs down in the tank and the cork floats on the fuel. As the fuel level lowers, the float lowers, altering the electrical signal back to the gauge on your dashboard.

When I removed my fuel tank I stuck an endoscope camera inside and did some tests to see how the arm and float of the sender behaved when fitted. Videos like this....

VIDEO: fuel gauge sender arm inside fuel tank

As you can see, when the arm is hanging at its lowest position ('empty' on the gauge) it REALLY is at the bottom of the tank. So 'empty' really does mean 'empty'. And I though the flat base of the float was probably significant to giving an accurate fuel level reading too.

My float was cracked and some of its shellac coating was coming off. I thought abut repainting with shellac but had read that it's not resistant to the ethanol in modern fuels. I thought about coating it with epoxy - but thought that would add weight to the float and alter its buoyancy. So I was on the lookout for a float solution.....

I'd seen plain, uncoated cork used.

(Credit: Jarno Muona)

I'd seen people replace the float with bits offcuts of closed cell foam - and that seemed to work.

Float made from closed cell foam

The Jaeger float is held on the arm only because of a wobbly section at the end and so a piece of foam is perhaps a good substitute if you're keeping the original arm.

And I'd seen some carefully made metal floats.

Homemade metal float (credit: Buttercup Bob)

Several years ago someone on Facebook found a cheap float on eBay and used the float off that. 

Modern plastic float (credit: Simon Broadhurst)

I bought one as well and squirrelled it away. More recently, I thought it wouldn't hurt to see if I could find a different sender float of about the same shape and size as the old Jaeger - with a flat bottom. And I found one! The float was about the right length.

And it was about the right depth. And used a slot in the end to stabilise the float - just like the cork original.

I thought about trying to bend and re-shape the long arm that came with it for use on my Jaeger, but found it just too thick to pass through the hole in the sender.

So I also bought some more sprung steel wire - the same size as my Jaeger arm - to make a new arm. Removing the Jaeger arm and cork was just a matter of opening up a couple of crimps. They were all that held it on.

I was careful to engineer the new arm so that - when fitted to the Jaeger, it hung down the exact same amount as the old cork float. 

Setting the arm length and height

I was really pleased with the result. But I'd forgotten one tiny detail..... the float was too big to fit through the hole in the fuel tank! It was too wide! So, ultimately, I've had to resort to using the 'barrel' float that I'd bought previously. 

Again I was careful to set the arm length and height so that 'empty' really does mean 'empty'.

I've refitted it in the tank now. New seal and a good earth contact.

The sender will end up sealed in the 'time capsule' under the seat, but I suspect I will still keep my eye out for a suitable modern sender unit - but with a smaller float.