LPG Discussion Forum

Car is an automatic, 55 plate citroen c3.

Has a BRC kit installed in 2008.

And is giving 19-20 mpg.

Just had the petrol side serviced, and am a bit lost why it is giving poor miles per gallon.

Have taken it over to a gas place and they have told me that it won't make any difference to miles per gallon, as what ever information is used for petrol the same info is piggybacked on for the lpg.

The car gear changing between 2 and 3 is very slow, and at higher speeds it starts running on petrol as appose to gas, but regardless it still gives the same mileage.

Any ideas what the problem could be?

It is my first lpg car.

Is it automatic or a sensor drive ?

Tubbs wrote:Is it automatic or a sensor drive ?

Hi its this

BLACK, 2005 CITROEN C3 SX AUTO 5 DOOR HATCHBACK

It's sensor drive I think (sx).
I had a right pain in the arse with one. Kept stalling as it was returning to tick over. But not all the time either.
Have they fitted a fuel gauge fix ? Or does it always think its out of petrol ?

Tubbs wrote:It's sensor drive I think (sx).
I had a right pain in the arse with one. Kept stalling as it was returning to tick over. But not all the time either.
Have they fitted a fuel gauge fix ? Or does it always think its out of petrol ?

It runs fine from petrol to gas, and from gas to petrol fine - automatically.

Does the fuel gauge register fuel or does it always think it's empty ?

Tubbs wrote:Does the fuel gauge register fuel or does it always think it's empty ?

yes the gas is very accurate though the petrol is usually accurate sometimes swing from one reading to the next.


the car keeps hanging between gear 2 and 3 the gears don't change upwards according to the speed. They tend to hang until you ease the peddle and then eventually they change gear.

Ok so back to basics what real time MPG are you getting on petrol? Do a run to measure consumption full tank to full tank. There is no point looking at the numbers on the trip computer

classicswede wrote:Ok so back to basics what real time MPG are you getting on petrol? Do a run to measure consumption full tank to full tank. There is no point looking at the numbers on the trip computer

Real time about 19-20 mpg without using the trip computer.

Well if you are getting 19-20 on LPG and Petrol only does 19-20 then that confirms the problem is nothing to do with the LPG system.

You should be getting 30+ on petrol depending on what your driving is like. Could be things like a dead lambda, blocked cat, stuck brakes or very knackered gearbox causing the consumption issues

Yes you should be looking at 30+ easy. The one I converted did in the region of 38.
Reason I asked about the petrol thing is that it proper messes about with the cars ecu if it's low on fuel (or thinks it is) all the issues I had, ended up being directly contributable to low fuel. Put some petrol in the tank. So the ecu magically "found" all the fuel that was already there and all was fine and dandy.
Once I fitted the fix for the fuel gauge it's not been a problem since.
Sounds like the sensordrive servos have lost their way, you could try getting the gearbox adaptivity reset and see if it makes it any better. I hate to be the bearer of bad tidings. But that sensordrive box with the flappy paddles on the steering wheel have a lot of issues. It's basically a manual box with solenoids and servos to operate levers to change the gears and press the clutch in and out.

Tubbs wrote:Yes you should be looking at 30+ easy. The one I converted did in the region of 38.
Reason I asked about the petrol thing is that it proper messes about with the cars ecu if it's low on fuel (or thinks it is) all the issues I had, ended up being directly contributable to low fuel. Put some petrol in the tank. So the ecu magically "found" all the fuel that was already there and all was fine and dandy.
Once I fitted the fix for the fuel gauge it's not been a problem since.
Sounds like the sensordrive servos have lost their way, you could try getting the gearbox adaptivity reset and see if it makes it any better. I hate to be the bearer of bad tidings. But that sensordrive box with the flappy paddles on the steering wheel have a lot of issues. It's basically a manual box with solenoids and servos to operate levers to change the gears and press the clutch in and out.

Thanks for the info above

Come to thing of it, the petrol fuel guage has been giving different readings randomly. It can show the fuel tank is full then you do a journey then when you switch it on again it shows the fuel guage is a quarter of a tank. Seems like its giving false readings sometimes. The lpg fuel guage is perfect on the other hand.

What is the fuel gauge fix you referred to ?


Thanks

My mum's 1.4 petrol Pug/Citroen drinks fuel and we can't find anything wrong.
Me thinks the reason why Citroen/Pug converted the petrol Berlingo type vans to LPG was because of poor mpg.
20mpg is a bit rough though, could believe it in the vans. I still think 25-30mpg average is all you will get in a medium car on lpg, all I ever got.

I once diagnosed and fixed a malfunctioning ECU on a petrol Citreon, I think C3. I've heard some Citreon ECU's are prone to faults...

In this case the car would start fine and run OK until it started to warm up, then gave increasingly poor mpg until finally it stopped running. The owner took it back to the person she bought it from (who is a mechanic but a bit old skool so I do most of his electronics diagnostics) and he changed the coolant temp sensors but that didn't fix the problem so he brought it to me. I found the ECU feed voltage to a temp sensor was wrong and since the sensor simply pulls down this voltage to give the ECU it's temp reading it was interpreting a very cold engine all the time. I fixed it by making a little op-amp circuit that buffered the sensor voltage back to the ECU, so the ECU again could interpret correct engine temperature. I'm not saying this is the fault with this car but if it is it could explain the poor economy... The mechanic had previously looked into a new ECU but apparently that would have cost £700, the fix didn't cost a tenth of that including my time etc. Still more likely that the problem will be something more main stream like one of the things others have suggested (cats probes etc) but worth mentioning.

I also learned that some model/year Citroens left the factory without a petrol filter fitted... Not good but not your problem if you have the same poor economy on LPG.

Simon
www.Lpgc.co.uk