Fuel tank sender unit

[stuartgb100]

According to my March '70 workshop manual (Lotus), I do not have to remove the tank in order to change the sender unit. Section L4 explains the procedure. It refers to the removal of a centre lock ring.

Before I get too far into this ...... is this correct?

The replacement sender unit appears to have no such centre locking ring, merely a series of holes around the perimeter, and a matching gasket. From what I can see, the existing sender unit is the same.

So, can it be done with the tank in-situ?

I'm guessing my version of the manual did not cover the later Sprint variant.

Regards,

Stuart.

[miked]

Stuart,
I would say No. Mine is as you describe. It sits facing the front of the car and is well down in against the glass fibre. After you have change/worked you will want to verify fuel tightness. I had mine tipped on it end in the garden so the fuel went against the gasket to ensure no leaks. Since it is a bit of swine of job to move the rubber pipe and slide the filler neck, I would not want to repeat it due to a leak.

I have an early spyder tank and the little brass screws go right through into the fuel. Means that even with your cork gasket etc it is easy to get a leak down the thread. Some thought should be given to some kind of sealant that resist petrol on the threads. I intend on re sealing mine as when I had the rear jacked last yaer I had a bit of a weep from the sender area.

Mike

[stuartgb100]

Mike,

Thanks for that. Fuel for thought (poor pun intended)!

Any ideas on the sealant for the screws?

Regards,

Stuart.

[Emma-Knight]

tiny copper washers under the screw heads maybe?

[miked]

Yeh Emma reminded me!

I forgot to mention that mine have tiny little brass washers . I think I spent about 20 minutes looking around in Halfords to find something. I think it was a threadlock product by loctite that will withstand petrol. I cant put my hands on it. Like i said I have not been back into do it as it seemed to seal. Perhaps the cork swelled. I do intend to have ago at a reseal this summer.


Mike

[stuartgb100]

Thanks to all for the suggestions.

I've removed the tank and sender unit. PO said he'd fitted a new sender ..
... not at all sure about that. Anyway, the float was holed. New sender and cork gasket now fitted.

Tank on one side in the garage with a little old petrol in it. No leaks yet, so fingers crossed.

Yes, there were little stainless steel washers with the old securing screws. Trying a dry seal with no gasket sealer.

Regards,

Stuart.

[gjz30075]

Best sealant I found for this application was the stuff that doesn't harden. It begins with an 'H' but, its on the tip of my tongue, can't remember it. Help!

Greg Z
'72 Sprint

[M100]

Hermetite? the golden stuff doesn't harden, the green stuff does, the red stuff is semi-hardening.

or Hylomar? non setting similar to Hermetite golden but comes in blue

[stuartgb100]

The new sender unit was on test overnight in the garage, with a little petrol in the tank.

The seal has held up well, just using the new cork gasket, screws and the little washers.

Fingers crossed.

Regards,

Stuart.

[gjz30075]

Yes, Hylomar! Thanks! Senior moment there, sorry.

Greg Z
'72 Sprint (I think)

[elansprint71]

Greg,
Clitoris?

Pete.

[gjz30075]

Thanks Pete. That's certainly a memory perk up!

[Matt7c]

I obtained a new sender unit from Paul Matty's last year, but I think it must be for a later model (as is so often the case for S1/S2 owners!). As I recall it had 3 terminals, but I had only 2 leads. The resultant display is a little scatty, although I have come to understand it.

When the tank is completely full, the guage reads nothing (ie, the pointer is at 'home' well left of the E, like the sender isn't sending). When the tank gets gown to a certain level, the gauge jumps into life and starts to record Full (which isn't true). Shortly ater, the gauge starts to read halfway and thereafter it records lowering fuel levels (although I haven't tried to find out how full it is when it starts to say half). I never get any reading between half and full. I assume that this has something to do with the exposed contacts on the inside of the sender (ie when the float and arm raise and lower, a copper contact crosses a selection of stationery contacts). I admit to being surprised at this design which seems to me to be capable of producing sparks (not good inside the fuel tank) and being shorted when submerged in petrol (hence no reading before half full?).

Anyone have any idea what is going on and how to get around this?

[john.p.clegg]

I think a little "setting" of the arm was required before fitting as it seems that at full it's going off the rheostat windings.....

P.S. don't worry about petrol shorting it or sparks.....
There is no problem

John

[Matt7c]

I think a little "setting" of the arm was required before fitting as it seems that at full it's going off the rheostat windings.....

Aah, that makes sense. "Setting" the arm can go on the list for a rainy day...thanks.