My Fuel Gauge Can't Make Its Mind Up

[Beejay55]

My car runs on LPG, so I expect the petrol gauge to drop a little as it burns petrol initially, until it can switch to LPG.

However, on occasion I have noticed the petrol gauge dropping slowly even after the car has switched to LPG. This seems very confusing as I cannot see how I can be burning petrol and LPG simultaneously,unless I am burning one fuel, and leaking the other. The gauge can drop by almost a quarter of a tank over my 65 mile commute to work. On most journeys this does not happen, just occasionally. I have given it some thought, and cannot determine any pattern as to what might cause it.

If that seems strange, what is stranger is that usually at some point, I will glance down at the petrol gauge and the needle will have returned to its original position. I am confident that I am not leaking either LPG or petrol.

I wondered if anyone else has experienced this? Not unduly worried about making a repair, unless that turns out to be cheap and simple. I am content to live with this 'feature' of my car.

Any suggestions?

[bookend]

The gauge will drop when running on LPG as the computer still thinks the car is running on petrol as the fuel consumption is calculated on the number of injector openings.

Periodically the level is corrected to the float level and you will see the gauge jump back up. The level is always corrected if you were to put petrol in the tank.

Its perfectly normal and nothing to worry about.

[Bluesman]

I remember seeing in an LPG forum where the car was running on both at the same time and despite being told by a couple of LPG installers thats impossible it cant happen eventually he found an LPG engineer that new what he was doing and indeed it did turn out he was running on both at the same time.

Might not be the same problem that you are experiencing but maybe worth a look at. Mike.

[TigerFish]

As per bookends post, the gauge doesn't use the float in the tank all the time, the ecu controls it the majority of the time with periodic corrections from the float. No idea why it needs to be so complicated other than it stops the deviations when cornering etc with sloshing around in the tank.

Sent from my Iphone using Lexus OC

[bookend]

If the level jumps back up periodically then it wont be using both petrol and LPG otherwise the petrol level wouldn't correct itself.

There doesn't seem to be a pattern on the 430 how often it will recalibrate the level with the float.

This has been discussed a few times on here if you search.

[Beejay55]

Thanks all. My curiosity has been satisfied.

I was not worried, but could not think why it might appear to go up and down like that. As TigerFish says, rather an overly complex system for such a simple requirement. It seems that it is using complex technology, just because they could, not because they needed to.

I guess that the data is being sent to the onboard computer to accurately display average consumption etc, and they are using it to also drive the analogue fuel gauge.

[Beejay55]

If the level jumps back up periodically then it wont be using both petrol and LPG otherwise the petrol level wouldn't correct itself.

There doesn't seem to be a pattern on the 430 how often it will recalibrate the level with the float.

This has been discussed a few times on here if you search.

Steve

Apologies, I should have done a search first, but this seemed such unusual behaviour I did not think that it might have already been fully discussed and that my 'problem' was a shared one.

Lesson learned :)

[bookend]

No need to apologise the forum is great for finding out about our cars.

At least you now don't have to worry and just enjoy the car.

[Chris Skelton]

Ah, for the simple days of early cars where you stuck a stick into the tank!

[Beejay55]

Ah, for the simple days of early cars where you stuck a stick into the tank!

I used to put petrol in mine !