SV Sigma 150 fuel gauge inaccuracy

[brianmurray325hotmail.com]

my 2007 Sigma 150 SV has had an inherent inaccuracy in the fuel gauage reading from day one when i got the car factory built from CC. I wasn't fully aware of it until my round trip to le mans this month (the car gets little use involving more than a 60 mile run and i tend to keep it topped up). i believe there were issues mentioned some time ago but i didn't think it involved my car. Has anybody had a similar problem and got a "Fix"? Is it a compatability issue between the sender and the gauge? Several fill ups on the Le Mans trip give me the impression that there's something like a 20%, its been showing "hard down on empty" and i've had a 100 more miles or so out of it. 🤔

[DJ.]

I have a 2010 Sigma 125 which I'm pretty sure has a similar combined pump/sender, and the fuel gauge gives a good idea of the fuel in the tank. I checked it as I filled it for the first time after reading how inaccurate they are.

 

So between 2007 and 2010, Caterham fixed this problem and hopefully should be able to tell you how to improve your set up.

 

Duncan

[RedCat7]

My 2011 150 SV has this problem. The fuel gauge is on empty after 150 miles. I just fill up every 200 miles but even then I struggle to squeeze in 30 litres. Owners handbook says the tank capacity is 41l. I'll probably never bother to sort it unless somebody has a simple solution?

[Domus]

Sigma 150 S3. When needle is hard left I can never get more than 28 litres in, as the odometer is inaccurate I have a bike speedo I reset at each fill up and fill up around 200 miles. Last week I came back from France. Filled up in Honfleur then chickened out on the M6 Toll at 220 miles. Managed to squeeze in 27 and a bit litres. Question, can you use the last 5 litres in a Sigma tank? Has anyone ran the tank dry? If so how much did you squeeze in?

[TobyCoulson]

Same problem with mine. When it's showing past empty I can rarely get more than 25l in it. Given up caring tbh

[Jonathan Kay]

How about a little electronic module between the sender and the gauge that allows you to set the gauge reading when the tank is physically empty and full, and then applies those offsets?

 

Jonathan

[Scoops]

Same here with my 57 plate SV.Never get more than 25 -28 in.

 

I keep thinking of taking a 5l can of fuel with me and seeing how far I can get until dry but never get round to it.

[Alan Reeves]

2011 and its still the same issue, SV

 

200 for top

[John Vine]

Welcome to the wonderful world of 7s. My 1.8K SS-R had a pessimistic gauge, and the one on my R400D is comically so. It reads 3/4 with a full tank and minus 1/4 when there's two galls still in there. Over the years, I've learned to ignore the gauge altogether and drive on the tripmeter.

 

JV

[CB]

"Question, can you use the last 5 litres in a Sigma tank? " - the answer I was given by Caterham Midlands a couple of months ago is "no"

[colindavies56]

2010 150 S3,when my tank was low i started up the car and syphoned it till it cutout,then carried on syphoning till no more left and i got an extra 2 ltrs out.

so we have a usable 34 ltrs,IF YOUR BRAVE.

[Domus]

So assuming 35 mpg, a tank will last 259 miles, I'll carry on re filling at 200 miles which should allow for a little "progress making" now and again.

[sjmmarsh]

My 2001 SV and 2007 CSR both do this - don't worry about it. It just means that I fill up when the tank get into the '1/8th of a tank left zone' and put in just over 32 litres.

 

It means that you won't suck the dregs out of the tank, and in theory I have about a 40mile range when he tank show empty.

 

I did nice have trouble finding fuel and the gauge was showing about 1/8th below empty. It still only took 36 litres though. Just use the trip meter and allow for how you have been driving, as others have said.

 

Steve.

[charlie_pank]

I think they all do that to some extent. I normally use both the fuel gauge and the trip meter to decide when to fill up. It's not like these modern things that guess how many miles miles you've got til fill up.

[Garry7]

2012 175 SV - ran out on motorway last week, gauge still not at the bottom of red.

Got 37.5 ltrs in so I make that 4 ltrs unusable. Clearly hadnt been getting it full at previous fill ups as it had only done 188 miles when it stopped.

 

At least it was the only nice evening we had last week so didnt mind waiting for the tow.

 

Will use the 200 between stops rule going forwards I think.

[Dr Slotter]

I have a 2009 175 SV and ran out of the first time last weekend, fortunately the car was sat idling in the Silverstone paddock! I put about 4.5l in from a can, then drove about 8 miles to the Towcester/A43 BP garage where I brimmed it with about 32l. I have also noticed in recent weeks my guage has developed a bit of a 'wobble' in that it will changed it's reading randomly, especially in the bottom half.

 

Edited by - Dr Slotter on 22 Jul 2012 20:29:52

[diggerman]

When I built my Sigma 150 it needed about 4 litres before it would start, so guess that much of the tank is un-useable. If I run it to the bottom of the red section it will take about 28litres to the brim. So the safety margin is about 10 litres which is perhaps not unreasonable. I therefore drive with confidence to the bottom of the guage.

 

Never run out so far.

 

Peter

[TobyCoulson]

You should drive with confidence everywhere and not just to the bottom of your fuel gauge

[RedCat7]

Is there a way to re-calibrate the gauge or sender?

 

After running out of fuel on Sunday, 170 miles after filling up I need a better solution than filling up every 200 miles! I find that every now and then a petrol pump does not want the properly fill the tank.

 

 

[Jonathan Kay]

*arrowup*I don't understand. How will recalibrating affect your range?

 

How about marking the glass on the gauge with gallons from empty using something like Letraset or bits of tape?

 

Jonathan

 

[RedCat7]

Re-calibrate it, so that it is accurate. Right now it reads empty when the tank is half full.

[michaeljclark]

Hi RedCat7

i generally find that I get more success when filling the 7 up if I use 1/2 a squeeze on the pump handle so that is not at full flow, I also don't insert the nozzle all the way in, I pop it just into the filler and angle it down, I then kneel or squat down behind the 7 whilst keeping a beady eye on filling it up until it's full to the brim.

My ggage is wildly inaccurate as SM25T and Stu Innes can attest to from our recent Euro trip, the gauge on my Sigma engined SV starts to fall slowly, until it hits 1/2 way then rapidly falls to 1/4, slows down and between a 1/4 and the red and then falls very very slowly, whereas SM25T and Stu's gauges, fell inline with mine to 1/2 a tank and then kept going at the same pace.

We recon the sender is the issue, but I think I chickened out @ 220 miles with the needle in the red, before filling up and I only manage to get 37l into my SV sized tank (que the calls that I wasn't trying hard enough)

I think it's a case of TADShttp://www.lotus7.club/sites/all/libraries/ckeditor/plugins/smiley/images/whatchutalkingabout_smile.png

Mike

[slap_ed]

Sigma 150 2009

The accuracy of my fuel gauge was something that kept bugging me. Mine would drop a little too quickly and arrive in the red sector prematurely, then It was always, shall I, shan't I fill it up, or dare I risk it a little further?

I removed the fuel pump from the tank and slightly bent the float arm downwards. This allowed the fuel level to get lower before the gauge read empty. It's early days yet and I haven't had much time to test the results yet but it appears to be much better. Now it stays on full for longer and runs out of fuel on or near the bottom of the red sector. I need to test this further as I didn't record the miles covered or how many litres I got back in.

Haven't used the car much but will report back when things are a bit clearer.

[Domus]

Interesting, can you say how much you bent it? Did you just put a kink in the wire?  Might give it a try.  In assume the tank was almost empty when you removed the pump.

[slap_ed]

I did this with the tank 3/4 full which was a bit silly. The steel float arm disconnects from the pump body quite easily. I bent it so the float position ended up approx 1" lower and to help the float utilise the full travel I also rotated the pump body with float towards the front of the car, but be careful because going too far will cause the float to foul the rear tank wall.  It was purely guesswork, but it seemed to do the job.

When I fill the tank the gauge pointer now stays at the full mark for a lot longer before it starts to drop. I actually ran this first tankful low, to the point where the next morning it wouldn't start. The gauge pointer was at bottom of the red empty marker.

I need to record mileage and litreage next time so I can confirm my initial findings.

One thing you can't do (well not easily) is adjust the fuel pick up point. The car will run out of fuel at the same point before and after this adjustment. This method makes the indicated fuel levels a bit more believable. But it's early days yet, I'll need to replicate this a few times to convince myself.