Lotus Elan

level fuel sensor

PostPost by: lotusbzz » Mon Apr 29, 2019 1:30 pm

Good evening to all Elan Community!

I did purchase a new fuel level sensor, but I'm a bit worried about the construction of such part because it's all open, the potentiometer inside the case is in contact with the petrol, no sealed, for sure is not EEX explosion proof .

fuel-sensor-1.jpg and


Can anybody explain how it works?

fuel-sensor-3.jpg and


fuel-sensor-2.jpg and


For sure inside there is a point of contact where the movable stick scratches the variable resistance of the potentiometer: what's happen if a spark is originated by this friction point?
Ok you could say that the tank is vapour saturated and there is no oxygen inside, but before light my cigar with my own baby Elan, it would be great to get some comfort from you all.
thanks

Ciao da bella Italia
Paolo
lotusbzz
Second Gear
Second Gear
 
Posts: 70
Joined: 01 Mar 2015
Location: Italia

PostPost by: billwill » Mon Apr 29, 2019 2:55 pm

That worried me too, but they are all like that and given that I have never heard of a fuel tank explosion, I guess they are safe after all.

:shock:
Bill Williams

36/6725 S3 Coupe OGU108E Yellow over Black.
billwill
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 4568
Joined: 19 Apr 2008
Location: London UK

PostPost by: Craven » Mon Apr 29, 2019 3:28 pm

It’s a long time now since I needed to do the calculations but I think you will find the answer under Intrinsic Safety.
Basically not enough energy available to cause problems.
Craven
Fourth Gear
Fourth Gear
 
Posts: 882
Joined: 14 Sep 2013
Location: south coast uk

PostPost by: 2tmike » Mon Apr 29, 2019 4:03 pm

These rely upon the vapour space above the tank contents always being above the upper flammability limit of petrol and therefore non explosive/flammable.The level sender itself is quite capable of generating a spark as it is connected to the car's 12V electrics with almost unlimited current available!! To be designed as intrinsically safe would require supply through zener barriers or other devices to limit to around 1.5V and 0.1A. Even if your tank is empty the vapour will stay above the upper explosive limit unless you start blowing air into it .........
2tmike
First Gear
First Gear
 
Posts: 41
Joined: 09 Oct 2018
Location: UK

PostPost by: Craven » Mon Apr 29, 2019 5:16 pm

Tank unit has the resistance of the gauge in series.
Craven
Fourth Gear
Fourth Gear
 
Posts: 882
Joined: 14 Sep 2013
Location: south coast uk

PostPost by: 2tmike » Mon Apr 29, 2019 5:44 pm

Very true, but the minimum ignition energy for petrol vapour is about 0.8mJ or 0.001watt seconds.....not a lot at 12V
2tmike
First Gear
First Gear
 
Posts: 41
Joined: 09 Oct 2018
Location: UK

PostPost by: miked » Tue Apr 30, 2019 7:21 am

2tmike.
Brings back my mining electrical career with Intrinsically safe equipment. :D
Same script with methane and flamable mixture range. Small volatile window. Lots of zener barriers, low voltages power supplies with high impedance and even atmite discs in signal bells to quench back emf.
An interesting point was the creation of an incentive spark created by the blow of and object against silver paper on metal. The cause of an explosion! Demonstrated with a hammer blow. So much so that silver paper was contraband. Our Kit Kats, Wrigley spearmint chewing gum and various chocolate buscuits were supplied in paper.
Sorry for thread drift but it brought back some memories.
Mike :D
Last edited by miked on Tue Apr 30, 2019 7:36 pm, edited 1 time in total.
Mike

Elan S4 Zetec
BSA B33
Suzuki Hustler T250
BMW rninet scrambler
Suzuki TC120 trailcat
User avatar
miked
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1130
Joined: 29 Sep 2003
Location: Northwest UK

PostPost by: 69S4 » Tue Apr 30, 2019 8:10 am

I know that absence of evidence isn't the same as evidence of absence but I'd guess that the fact that we, as well as the owners of countless other vehicles using the same sender technology, are still here is some comfort. The odds look as though they're on our side. :)
Stuart Holding
Thame UK / Alpe D'Huez France
69 S4 FHC
Honda GoldWing 1800
Honda CBX1000
Kawasaki H1 500
Yamaha XS2
69S4
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1113
Joined: 23 Sep 2004
Location: nr Oxford UK

PostPost by: rcfurse » Tue Apr 30, 2019 9:43 am

Do check the unit VERY carefully before you fit it. You will see in the photos that there is a circular plastic grommet which the terminals for the electrical connection passes through. The second wire connects to the body of the unit.
I recently purchased one of these from one of the bigger parts suppliers and fitted it. Fine until the tank was filled above the level of the gauge. At this point fuel poured out.

As it was an older tank I assumed that the boss on the tank had failed so I emptied the tank, removed it and ordered a new one (Gulp £££££). When it arrived some 6th sense told me to check the whole thing once I fitted the sender to the new tank so I put a gallon in and then tipped the tank so the fuel was over the gauge. Fuel poured out.
So I looked at the gauge which was virtually brand new. It had TWO plastic grommets for terminals but the second one had no terminal, just a slot in the plastic for the blade but which the fuel was pouring through. When I called the supplier and they asked the mechanics they said "Oh, we have had a few like that. We just use a soldering iron to melt the plastic and seal the hole". Grrrrrrrrrrrrrrrrrr

So check your gauge before you fit it!
Richard Furse
Funemployed in N Wales
S3 DHC
S4 DHC
S4 FHC
S4/Sprint
340R
SID
14 "others"
rcfurse
Second Gear
Second Gear
 
Posts: 89
Joined: 30 Dec 2018
Location: North Wales

PostPost by: miked » Tue Apr 30, 2019 10:01 am

My point reinforcing 2tmike's point about volatile mixture not being present.
No worries!
Mike

Elan S4 Zetec
BSA B33
Suzuki Hustler T250
BMW rninet scrambler
Suzuki TC120 trailcat
User avatar
miked
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1130
Joined: 29 Sep 2003
Location: Northwest UK

PostPost by: Craven » Tue Apr 30, 2019 10:41 am

I understand why but what has ignited? Our tanks are vented to atmosphere.
https://www.youtube.com/watch?v=6A5qUir3b2k
Craven
Fourth Gear
Fourth Gear
 
Posts: 882
Joined: 14 Sep 2013
Location: south coast uk

PostPost by: 2tmike » Tue Apr 30, 2019 5:22 pm

Most likely displaced vapour from filling the tank. Vapour mixes with air just outside the fuel filler and somewhere around there will be a mixture within the flammable range. Then an ignition source from an electrical device or static and off it goes....
2tmike
First Gear
First Gear
 
Posts: 41
Joined: 09 Oct 2018
Location: UK

PostPost by: PaulH » Tue Apr 30, 2019 5:58 pm

If it's of any use I show the fuel level sensor in this video: https://youtu.be/yKiuTU5hZTE
Mine is an Elan S2. I think the later Elans have a different resistance sensor to mine.

Regards,
Paul
66 Elan S2
PaulH
Second Gear
Second Gear
 
Posts: 92
Joined: 08 Apr 2009
Location: Derbyshire, UK

Total Online:

Users browsing this forum: No registered users and 2 guests