Aprilia petrol tank sender. How I made one.

[Spanner Man]

Petrol tank sender.

My Lancia Aprilia came without a sender in the petrol tank and being an unusual car it shows the petrol level in a series of nine lights which illuminate depending on the amount of petrol.
Buying the device is impossible but I did find a diagram showing how it works.it uses a float connected to a string which comes out of the tank then around three pulleys the last of which has nine contacts to electrical wires. The string tension is controlled by a delicate spring. As the fuel level drops the pulley turns to contact with a needle and in doing so turns on a  bulb.
My home made version is much simpler with only one moving part. It consists of a foam float which slides freely up a rectangular aluminium tube. The tube is 5mm shorter than the distance from the top to the bottom of the tank and it is sealed with weld at the bottom. Inside the tube are nine magnetic switches as you would find in a typical alarm system. Embedded in the foam is a magnet. As the float moves it triggers the switches which illuminate the diode lights in the dashboard. To see this working please look at this video.
https://youtu.be/FBF74hB_9MQ

[brian]

I love it!
My S1 has a similar system without a sender and a very tatty gauge.
How do you weld up the aluminium square tube with magnets in or ar they threaded in with spacers?
Do you take commissions?!
Brian

[Mikenoangelo]

Very impressive - lovely job.

Mike

[Spanner Man]

Hi,
It was aluminium welded but you don't need to make it out of aluminium. Make it out of plastic pipe. Just be sure it is petrol proof and when you put in an end cap leave it in petrol for a month to be sure.
The magnetic switches are held in a plastic strip 2cm apart. I'll try to attach a photo.
No I don't take commissions. Thanks

[simonandjuliet]

Very clever ....

[tzf60]

Excellent solution, and your YouTube video is brilliant!
 
Tim F

[brian]

Very many thanks for all your information - I am so tempted to have a go and the idea of plastic appeals as there must be plastics and glues that are petrol-proof so even an engineering incompetent such as I could be successful.

[Dave Gee]

This is an amazing solution. I am further behind and my Aprilia has a way to go, but I am looking to make such a device with a friend over the next few weeks. I will be able to bench test it without a problem, but it will need road testing. Brian, as we are close geographically, please would you PM me if you are interested.
Will keep everyone updated.
Stay safe everyone.
Dave

[Dave Gee]

   Have machined up the cap for the top of the tank today and ordered the other parts. I am hoping to leave the original tube that held the float, in place, as I think it will act as an 'anti-slosh' device. Having looked at my tank I now realise that I need to replace it, so if any one out there has one to sell, please let me know

  Dave

[Spanner Man]

I did consider using a small Thermos flask to hold the magnetic switches.
Decided against it.
I also considered a design using no moving parts. Not even a float. Using these petrol level sensors set one above the other.

Automotive fuel level sensor fuel pump alarm sensor
https://a.aliexpress.com/_BSAqNj

[Dave Gee]

Please can someone tell me what sequence the lights originally worked in. There are at least three options I can see:
1 They stay on when the petrol tank is full and off as the level lowers
2 The reverse of 1
3 A light comes on as a new level is reached and the previous one is switched off.

Any views?
Dave

[simonandjuliet]

I am pretty sure that the original system of lights worked only when the button was pressed ( press on/release , not on/off) and the light corresponding to the level illuminated on the dash. Sometimes if the connector bridges 2 terminals on the dial above the float, then 2 lights come on
The reserve , square S2 or fan-shape S1, comes on automatically , whether or not the button is pressed

Hope that makes sense

[brian]

Dave, I think you are right. I do not feel that Lancia would have had light/s glowing all the time.  In the parts book (of which I only have ones in Italian and French and for S2) there is what I think is labelled as a switch.

[Sliding Pillar]

I agree with Simon.

[Foggitt]

My S1 is as Simon’s, with the lower right button to press to see the fuel level.
Andrew