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too fast response on fuel guage


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Hi 

My Lotus esprit SE chargecooler has a fuel gauge that responds very quickly to any movement of the car (fuel)

 

I get approximately the correct reading when stationary on flat ground but if I wobble/bounce the car the fuel gauge displays moment.

 

this is fine but irritating when going on a long journey.

 

Do they all do this?

 

I have checked the sender unit and it gives a smooth resistance change for a change in position.

 

as does the gauge.

 

I do not know If I have the correct tank installed as the previous owner fitted a new tank and the sender unit position does not line up with the hole in the plywood tank cover.

 

I am wondering if the tank does not have any baffles fitted?

 

Thanks for your help in advance.

 

 

 

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That's not the balance pipe if it happens when you bump a corner, it's not that dynamic.

 

There's a chap on here who sells a little box which electronically dampens the signal to the fuel gauge. 

 

http://www.thelotusforums.com/forums/topic/41307-vdo-fuel-gauge-anti-slosh-module-group-buy/

88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

For forum issues, please contact the Moderators. I will aim to respond to emails/PM's Mon-Fri 9-6 GMT. 

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It's like that on mine too and everyone else that I know - if it really annoys you, just make sure your tank is 3/4 full all the time :D

 

Although its probably smarter and cheaper to install the gizmo Bibs is referring to above - I'm gonna do it myself this year...

Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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I do not know If I have the correct tank installed as the previous owner fitted a new tank and the sender unit position does not line up with the hole in the plywood tank cover.

 

 

My SE is much the same. I can't seem to adjust the plywood cover enough to make it easy to access the bolts. I just use a variety of spanners and sockets to remove the sender (without removing the plywood board). The sender can be removed without removing other items (such as the seat belt reel), but it requires a lot of fiddling about. Note that there is only one way to fit the sender (the holes are not evenly spaced around the circumference). Be careful not to drop the washers in the tank (there are two per bolt).

 

I am wondering if the tank does not have any baffles fitted?

 

 

No baffles on the original. Custom tanks may have baffles.

 

I'm currently looking into fitting a tube type sender rather than a float type. I hear they are less sensitive. I've ordered a custom made one from Isspro Inc in Portland, Oregon (USA). If it proves to be a good solution, I'll post the specs here, although the company won't let me tell you the price. Unfortunately, they can't match the plug on the car (obsolete), so I had to order a generic car plug on ebay. Fortunately, I have a crimping tool to suit.

 

http://www.ebay.com/itm/251339766824?item=251339766824&viewitem=&sspagename=ADME:L:OC:AU:3160&vxp=mtr

 

A few years ago, I had my sender refurbished, but it was even worse than before. The trigger point for the low fuel light was way off.

 

Hopefully I can give a report in the next month or so.

 

Cheers

Ian.

Edited by Qavion
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That electric gizmo I posted up about costs £20 and is a simple fit. Much easier than fitting a tube sender although it won't help your low fuel light issue.

88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

For forum issues, please contact the Moderators. I will aim to respond to emails/PM's Mon-Fri 9-6 GMT. 

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I am surprised to discover lotus sold them like that and did not get any complaints.

 

I wonder if lotus ever issued a fix for dealers?

 

Even my old 1968 Europa had a stable fuel gauge.

 

The tube type sender sound like an interesting way to go.

 

Might try a big capacitor probably needs to be 20-30,000uf to give a long enough time constant. or the damping module.

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  • 1 month later...

Update: Just fitted my custom ISSPRO sender with additional output for the low fuel light. The sender arrived quite quickly, but the electrical plug I ordered on eBay from China took 7 weeks to arrive!

 

On the upside, there is no more fluctuation due to fuel sloshing around in the tank. Brilliant! On the downside, I still have that intermittent fault which makes the needle jump 1/4 of a tank. It has to be some kind of wiring problem. Perhaps a fautly common earth.

 

In the wiring diagram, the gauge has three terminals. One is power in. One goes to the sender. The third is an earth, but I can't figure out why it needs one (???). The earth line seems to be connected to another gauge's earth.

 

Anyway, I thoroughly recommend the ISSPRO sender. The guys there put a lot of effort into getting the product right. When ordering, just tell them:

 

9" tube type sender.

Resistance range: 10ohms (empty) ~182ohms (full).

12volt system

Low fuel alarm is an N/O (normally open) switch. i.e. With the tank above empty, the circuit is open.

They even provided me with an official diagram:

 

http://www.iinet.net.au/[email protected]/Lotus/LotusEspritISSPROFuelSender.pdf

 

Because the tank is 10" deep and the sender 9", the gauge will show empty with about 1" of fuel in the bottom of the tank (a nice 50km buffer, I'd say). Their tube type sender comes with phillips screws instead of bolts, but this makes it easier to fit. You just need phillips screwdrivers of varying lengths. The bolt pattern is standard VDO.

 

Anyway, hope you find this useful, guys.

 

Cheers

Ian.

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Thanks, Derek. Makes sense.

 

Just wondering where to go from here. It's not easy to faultfind. The wiring runs the length of the car and is linked to other systems. And I can't always rely on the wiring diagrams. All Esprits seem to be different.

 

Sometimes the low fuel light dims, but I don't know if that is related or another fault. I've tried to isolate the low level circuit by pulling out the low fuel delay module... but the lamp holder is still in the the line with the module removed and may have some kind of short, affecting the level indications.

 

Cheers

Ian

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The SE, S4, S4S and GT3 wiring is all very similar. The low fuel warning lamp dimming sounds like a supply or an ground issue (usually a ground issue on our fiberglass cars). The sender low fuel is just a switch and should be either on or off. It can oscillate due to the fuel sloshing around which is why there is the low fuel warning lamp delay module fitted. I have not looked inside this module but I expect it is a simple 555 timer circuit. I would have thought that pulling the module should prevent the low fuel warning lamp from being illuminated.

Edited by sailorbob
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The sender low fuel is just a switch and should be either on or off.

 

 

Correct. The original sender had a small resistance 10~20 ohms if i remember correctly, but the new one has 0.5 ohms

 

It can oscillate due to the fuel sloshing around which is why there is the low fuel warning lamp delay module fitted. I have not looked inside this module but I expect it is a simple 555 timer circuit.

 

 

Correct. It's a 555 timer.

 

Now that the slosh effect has gone with the tube type sender, I could try bypassing the timer completely (if required).

 

I would have thought that pulling the module should prevent the low fuel warning lamp from being illuminated.

 

 

True. Power is permanently on one side of the lamp (ignition on), but the delay module provides an earth. I was just thinking that a faulty lamp circuit or holder might cause both problems. e.g. a partial short on the power side of the lamp (just enough to reduce the volts to the low fuel light and to draw current away from the gauge circuit). However, I just noticed that the dimming of the lamp doesn't seem to correspond with the gauge fluctuations. There may be two problems.

 

The gauge and the low fuel light have different earths, so, at the moment, I'm leaning towards a common power problem (or two separate problems).

 

Regards the wiring, the diagrams seem to be similar on the cars, but sometimes the car's wiring doesn't always seem to match the diagrams :huh:

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  • 2 weeks later...

Just wondering if anyone knows where the earth (ground) for the fuel sender is on an 89 SE?

 

The early Stevens series wiring diagrams show an earth symbol adjacent to the sender. My SE is not like this. The earth wire disappears into a wiring harness, similar to the S4. The S4 Esprit wiring diagrams show the earth wire going all the way to the other side of the car and then through the Engine Management Harness Connector (EMHC). However, I tried disconnecting the EMHC and the fuel indications were unaffected (indications normal).

 

http://www.iinet.net.au/[email protected]/Lotus/FuelGaugeCircuitS4.GIF

 

I also removed an earth on the engine block (close to the firewall) which I thought might be the earth for the sender, but, again, the indications remained normal.

 

I don't really want to remove 6 or more feet of black electrical tape to figure out where the black wire on the sender goes.

 

Hope someone has come across this problem before.

 

Cheers

Ian.

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I added a separate earth from one of the 6 sender  mounting bolts just  to make sure on mine I think it was to a spare loom earth connection nearby. Sorry cant remember which, it was 18 months ago. 

Edited by mdw
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The sender could be earthing through the tank and the braided earth strap that connects to the chassis.

 

Thanks, Derek, but that doesn't quite explain why the (original) sender plug has 3 wires attached to it, one of which has to be the earth (the black one) which disappears into a wrapped harness (going into the engine bay) and not to a point on the tank.  

 

I added a separate earth from one of the 6 sender  mounting bolts just  to make sure on mine I think it was to a spare loom earth connection nearby. Sorry cant remember which, it was 18 months ago. 

 

 

I may have to end up doing this, Malcolm, but I'd rather avoid it. At the moment, I'm still faultfinding (I don't know for sure if the earth is causing the problem).

 

Anyway, thanks for the input, guys

 

Cheers

Ian.

Edited by Qavion
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A good thought, but... The new sender appears to be electrically isolated. The top of the new sender is plastic (the mounting screws don't provide continuity between the sender and the tank). Also, the rubber/neoprene? gasket is an insulator.

 

As the 1/4 jump problem was there before and after the sender change, I think the old sender was also electrically isolated from the tank (relying only on the wire). I guess I could prove this by checking the old sender (resistance between sender plug earth pin and case should be low).

 

Cheers

Ian.

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Interesting.... Sounds like yours matches the paper diagrams I have.

 

Anyway, I rechecked the old sender and it does also use the tank as the earth route: The old sender plug's earth pin is shorted to the metal top of the sender.

 

The earth seems pretty solid at the moment. I might have to check each section of the harness between the sender and the gauge. 

 

Cheers

Ian.

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There are a load of multil pin connectors behind the A post trims that are worth splitting and giving a squirt of WD40.

post-1261-0-27122000-1394740038.jpg

Edited by mdw
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