Alternative fuel sender for bikes with fuel strips

[Bendy toy]

The fuel strip is notoriously unreliable. Sadly nobody has found a way to repair them or avoid them failing.

From around 2011, BMW chucked the whole idea and went to a tried and trusted float level indicator.

So my plan is to use an aftermarket gauge which takes a 10 to 180 Ohm input and use it as a fuel gauge. The OEM fuel strip will be spoofed to remove the yellow triangle.

Fuel strip resistance spoofer is somewhere in here http://bmwsporttouring.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=770085#Post770085

This is the gauge.
It's 35mm diameter and reads 0 to 100 from a 10 to 180 ohm input signal so will work with any sender using that range. If purple is too "interesting", they also come in black and silver.

http://www.ebay.co.uk/itm/Micro-Dig...381849?hash=item5b13554f19:g:OtUAAOSw~OdVdVey

This is the VDO universal fuel level sender unit.

http://www.ebay.co.uk/itm/VDO-Fuel-...722150?hash=item4646b11926:g:MogAAOSw1S9WfOwz

Now here's the first rub. The gauge needs to fit to the LHS fuel tank but this is where where the fuel pump sits. The pump may well be in the way. Wont know until its opened and checked out.

Another option might be the Twin Cam float mechanism. However, I need to know its max & min output values to see it it can work with a universal gauge.

So question is-
Does anyone know the max and min output values for the twin cam fuel level float? I need to know the resistance values.

 

[King Key]

Alternatively you can use the tripmeter like everyone else and save a hell of a lot of grief and expense.

 

[Bendy toy]

I already do that but the trip meter demands the tank is 100% filled. The mileage Im doing these days means I'm running around with a top heavy bike for a couple of weeks and its getting annoying. Short of commuting 50 miles each way to work I want to find a way to judge when the tank is getting low. Then I can just half fill it and have no worries.

To be honest a low fuel warning light would be perfect (as Yamaha use) but I've not found anything to deliver that.

I'm sure many more have the same issues. So I ask again if anyone could resistance test the outputs on a TC float type fuel sender.

 

[comberjohn]

Thought you were showing us your other 'side' with that purple gauge, bendy.
Can you tell us where it can be measured without dismantling half the bike?

 

[fatnfast]

Can't help with the resistance, but what about a low fuel warning light kit like this:
http://www.jegs.com/i/ATL/046/KS109L/10002/-1

Or make your own using something like this:

http://www.circuitsgallery.com/2012/08/water-tank-lowl-evel-alarm.html

 

[Bendy toy]

The jegs.com fuel cell link could be what I need. The only low fuel warning lights I've found work with a float gauge and light at a set resistance.

The TC fuel sender has a blue connector and looks like below. But I have no other knowledge as my bike has the lovely fuel strip.

It would have to be out of the tank and taken end to end to get the top and bottom values. I don't even know if it uses resistance values or has has some other signalling method.

http://www.rubbersideup.com/media/catalog/product/d/s/dsc_3353_6.jpg

 

[Deleted account 190920001]

I would go with the second circuit suggested above. I have something very similar years ago on a bike and it worked a treat. As the tank is plastic you will simply just run two probes together down to your desired level. You could use your existing strip as the support but divert the wiring to your probe. Simple and everything is still sealed as original. It will only cost a few pounds as well.

Putting that generic float sender unit in is going to be loads of hassle.

 

[TLSgazza]

I know of someone at the moment who is designing an adjustable fuel level sender using the Suzuki TLS standard senders from the tank,
The standard suzuki fuel level senders in the TLS first come on with a flashing light when the bike has about four litres left, then a solid light at 2 litres left, as his design will be adjustable it could be set at different heights to give a customised reading according to the type if tank, its all still being designed but is looking promising at the moment.

If this link works here's a picture of his design, by turning the screw from the outside you can raise or lower the sensors to the required position.

 

[Bendy toy]

Ok! My long post from last night seems to have vanished.

The discussion about that diagram at http://www.circuitsgallery.com/2012/...vel-alarm.html says the circuit does not work. It also seems to use water conductivity so unlikely to work on petrol or oil.

My fuel level is low so last evening, I removed the bike bodywork and whipped off the fuel pump and filler cap.

The pump body DOES have enough space to accept a VDO float gauge support leg. But I don't think there is enough space for the float to move. At the very least, it's likely to read 100% until the tank is 1/2 empty. A pole or stick type sender needs less space and a 200mm long pole sender will fit under the pump but it will still not see the full tank range.

I put a long dowel down the fuel filler hole and there is enough space to fit a longer pole type float sender from the side pod bottom right up to the filler cap area. But the top end would need to be fully immersed. Even if I was courageous (stupid?) enough to cut a hole in the tank, there isn't enough space under the body panels. So more info needed.
http://www.ebay.co.uk/itm/POLE-TANK...452280?hash=item4ac6d55f78:g:dGEAAOxyi3FR4Zvt

Honda used thermistors on many bikes. These heat up in air so the resistance falls, current flows and lights a warning lamp. In petrol they remain cool so no current flows. Honda had one for a low warning and another for "fill now or stop anyway". I believe Yamaha used the same on their 1990s bikes. Their resistive fuel gauge was rubbish but the low fuel light was always accurate.

 

[TLSgazza]

Honda used thermistors on many bikes. These heat up in air so the resistance falls, current flows and lights a warning lamp. In petrol they remain cool so no current flows. Honda had one for a low warning and another for "fill now or stop anyway". I believe Yamaha used the same on their 1990s bikes. Their resistive fuel gauge was rubbish but the low fuel light was always accurate.

That's the same as the Suzuki TL ones in my post above,
Mine has always worked perfectly, and if his adjustable design works it could be adapted to fit others.

 

[Bendy toy]

A metal strip bolted to the underside of the fuel pump base could carry any number of thermistors and be used to light LEDs on the dash. Could be plan, but being a tart I do fancy a proper fuel level gauge.

How about a string of 9 switches/devices with a suitable resistor between each one running from tank top to bottom? When all are off the display shows 10 Ohm. When all are conducting it shows 180 Ohm. Oh how clever. I've just invited a fuel strip.

After some Googling - the VDO scale shows zero at 10 ohm and 100% at 180 ohm. Thermistors would cause the scale to operate with zero at 180 ohm. Another way to sense the petrol would be needed.

Subject to some further questions, the pole type float sensor looks like the least cost option and the easiest to deliver.

 

[Deleted account 190920001]

You sure it's thermistors in the tank? Only way I could see this working is to always have a reference one in the bottom of the tank in fuel at all times. Fuel gets hot after a while with it being wrapped around an engine.

I have an early 90s 1000 exup that has some kind of switch/sensor in the bottom of the tank. It doesn't switch a light but turns the fuel pump off until you flick the reserve switch. Still works after all these years.

 

[Bendy toy]

Honda used thermistors on bikes such as the CX500 Turbo. They run quite warm but are small so use little energy. A warm thermistor conducts power so can light a warning lamp or do other stuff. The ones in petrol are kept cool so they don't conduct.

http://www.electronicspoint.com/threads/thermistor-in-a-gas-tank.123318/

A low fuel warning is always handy so I'll probably do something similar. But I also want that fuel gauge.

 

[Deleted account 190920001]

Ok I wasn't expecting them to be used like that, what a horrible idea! I was expecting them to be used more as a temp sender low power reference, not actually running a bulb through it.

 

[Bendy toy]

Thermistor is crude but fairly reliable and the bulb temperature is well below anything harmful.

I would like to find something that conducts the other way around. Thermistor resistance drops with temperature. I want something that switches as temperature rises - so its OFF in the petrol but ON in air ideally with switching effect.