Fuel Guage all of a flutter

[davedogfish]

Recently acquired an immaculate late '91 S3C and I'm absolutely delighted with it. Having resolved most of the inevitable 'niggles' that make a TVR a TVR, I'm just about to tackle a fuel guage that oscilates between full and empty whilst on the move. At rest the reading is worryingly accurate but if I rock the suspension up and down St Vitus' Dance sets in again.

As you guys are far more experienced in Tvrickery, I would really appreciate your help in understanding whether my problem is more likely to be: -

A. Faulty sender
B. Wiring fault
C. Faulty guage
D. It's a feature - they all do that, warning you that there's a petrol station within 50 miles

Thanks.

[phillpot]

D

[Griffinr]

Might be some useful stuff here http://www.pistonheads.com/gassing/topic.asp?h=0&a... guage sender

Its a common problem though mine is now fixed and just drifts up and down with corners.

Rob

[davedogfish]

Thanks Rob, The sender was my no. 1 suspect. I'll by-pass the sender to check a 'full' reading tomorrow morning (great this retirement lark!) then order a replacement sender if appropriate.

[Donnysoutherner]

Mine does the same, almosgt certainly the sender. Basically it should have a damper which makes it read the 'average' rather than 'actual' depth of fuel. if not, when you corner one way (right) it is full and when you corner left it is empty.

If you just go round a roundabout over and over you'll never run out of fuel!

[davedogfish]

Thanks Donnysoutherner it's looking like a new sender then - only problem is I've just filled the flippin' tank! It looks like i'll just have to drive round the roundabout the wrong way for a more rapid empty!

[Barkychoc]

At least if the gauge moves up and down there's fuel in the tank!

If anyone can get to their gauge terminals easily you could try an electrolytic capacitor across the terminals to smooth out the fluctuations.
Happy to send something if someone wants to try it.
Are both terminals on the gauge the push on Lucar type? Anyone got a pic?

[phillpot]

Barkychoc said:

If anyone can get to their gauge terminals easily you could try an electrolytic capacitor across the terminals to smooth out the fluctuations.

Chris, would it work down the other end, at the sender?

ETA forget that, guess its gotta go in parallel, across the gauge ?

Edited by phillpot on Tuesday 4th October 10:10

[v8s4me]

Barkychoc said:

If anyone can get to their gauge terminals easily....

By "simply removing the dash" I presume?

Sorting out the sender is on my winter "to do" list so I'll be interested to see how you solve this one Dave.

[davedogfish]

Thanks to all of you for your suggestions. I've now had a chance to by-pass the sender and, as suspected, the guage jumps to 'full'. I notice there is an unused earth tag on the tank above the sender unit, should this be run to the chassis and, if so, could its absence be a contributory factor to my overactive fuel readings?

[jwoffshore]

I also noticed the unsued earth tag on my tank when I was refurbishing it. The tank sits on rubber cushioning strips, so does not have any direct continuity to the chassis. I reckoned this was bad if there was some kind of static build up which casued a spark, so I fitted an earth lead to connect the tank to the chassis. It did not make any difference to the erratic fuel gauge and the car has still not exploded, with or without the tank earth!

The fuel gauge fluctuates at the best of times. Mine seems to be worse when the fuel is low and it jumps between 0 and 1/4. Once you have a working sender again, maybe slugging it with a capacitor might smooth it out - a few 100 microfarads I guess?? I didn't get around to trying that myself yet.

[davedogfish]

Thanks Jonathan,

New sender (and gaskets) on order but, I agree with you, I would be a little happier if the tank were earthed so I've taken a strap to the chassis.

I'll let you all know whether the new sender has had the desired effect but don't hold your breath as the
longest part of the job will be running down the tank to quarter-full.

Thanks again

[mikel003003]

You will find it is very hard to get it fuel tight I recommend adding some hermatite or simalar instant gasget to the shopping list. I applyed some waited ten minuets sqwidged in the rubber seal applyed some more waited a further ten then replaced the sealing ring.

[davedogfish]

Thanks Mikel,

Good old red Hermetite - I'd almost forgotten what it looks like - back in the sixties most engines of my mates and I had the stuff oozing from every joint. Duly added to shopping list.

[Barkychoc]

v8s4me said:

Barkychoc said:

If anyone can get to their gauge terminals easily....

By "simply removing the dash" I presume?

Sorting out the sender is on my winter "to do" list so I'll be interested to see how you solve this one Dave.

I guess you could try it on the tank terminals - but capacitors and water are not a good mix so don't leave it on there.

[oldgeebee]

Griffinr said:

Might be some useful stuff here http://www.pistonheads.com/gassing/topic.asp?h=0&a... guage sender

The Landrover part nr PCR 8822 offered as a replacement here is probably for the S1. Can this be used on the S3 or is there another alternative for the later cars?
GB

[DaveV8s]

Before fitting a new sender, whip the old one out and check the soldered joints on the board for hairline cracks and clean the face of any growths which could be shorting it out. You will probably find that the Landrover sender has the float in a different position which will require extensive re-bending to get right. Better to fix the old one but use a new tab and blue gasket sealer. Other than that you probably have a faulty gauge!

Oh check your earth as well!

[Gerald-TVR]

oldgeebee said:

The Landrover part nr PCR 8822 offered as a replacement here is probably for the S1. Can this be used on the S3 or is there another alternative for the later cars?
GB

Compared the landie one with an original and the range of movment appears different and the arm would certainly need considerable re-shapimg!! Its £25 from local indepenant landrover supplier and its worth noting that TVR Car Parts can normally supply (out if stock at present) OEM replacements (made by the same firm that did it for TVR) for about £35.

I have changed my original sender for a S/H one from the last project car as the original started showing 1/4 tank when it was empty. (resulted in running out of petrol - but luckly I was on drive at home) and linked the earthing point on tank to sender earth and then connected to wiring loom earth. I dont know if that might cause issues (dont think so) any advice please.

Norman

[B16JUS]

Whats the easiest way to get to the gauges.

I presume they either pull out or you have to remove the wood pannel to access from behind

Any help would be great

Thanks

J

[Oldred_V8S]

Barkychoc said:

v8s4me said:

Barkychoc said:

If anyone can get to their gauge terminals easily....

By "simply removing the dash" I presume?

Sorting out the sender is on my winter "to do" list so I'll be interested to see how you solve this one Dave.

I guess you could try it on the tank terminals - but capacitors and water are not a good mix so don't leave it on there.

Chris

What value of capacitor? I guess you could attach some flying leads to it and mount the capacitor out of harms way.