Lpg Conversions.

[daktari]

I`ve been offered a 1992 Range Rover 3.9 Vogue with LPG conversion.(Converted in 94) 140K miles. 11 months MOT. FSH. Air asisted suspension. Electric everything. Air con, leather etc for a very attractive price. Overall it`s a very clean example with absolutely no chassis corrosion and only the usual upper tailgate rot.

The owner is selling due to a new family arrival and cant justify having three cars. He`s a long time friend and i trust his integrity, so no problems there.

However. Apparently he had electrical gremlins with the car about a month ago. The symptoms were only apparent when it was running or trying to run on LPG. It ran OK-ish when switched back to petrol. The ignition system including distributor and coil were replaced with new items and this seemed to sort the problem out..... More or less.....

I took it for a drive today, using only LPG (Couldn`t find the changeover switch ) and it does run reasonably well. If it were running on petrol i would have said that it could do with a full service and tuning as it was a little hesitant to start - turned over for 5-10 seconds before catching.- and seemed a little hesitant on acceleration. Obviously a Rangy is a big old lump, even for a 3.9 litre V8 to drag around but it really seemed to be holding back.

So after all this rabbiting on what do i want to know?

1/ Apart from being 30p a litre cheaper than good old U/L, how does LPG affect fuel consumption?

2/ Are there any known reliability issues with LPG?

3/ Would LPG affect the longevity of the engine?

4/ How long can an LPG conversion be expected to last before parts wear out or need replacing?

I think thats about all i can think of for the moment. Thanks for sticking with it if you`ve got this far and hopefully someone more knowledgable than me can give me the answers i need.

TIA

Dak.

[jaxx]

1) roughly the same

2) not really no

3) no

4) as good as any engine part, just one extra thing to keep an eye on, the thing that you must be aware of its the thing thing that controls wether its using gas or petrol

sorry to be a bit vauge, its a good conversion on an engine like that as itll make up on the fitting costs within 2 years

also you loose around 10% of the engine power as opposed to if it were running on petrol

ie if petrol was 200bhp youd only see around 180 with LPG

[martin_longbow]

Got me certificate abour 6 years ago for fitting LPG systems, havent done any for about three years.

Depending on the system fitted it could be injection but it is likely to be a simple mixer system. There is likely to be a brain to your gas system, which will be connected to the throttle positioning sensor, and or the lambda sensor. The gas will be regulated before the mixer by a type of stepper motor.

Wen u hit the switch it should start on petrol and switch to gas around 2000 rpm. You should hear the your relay switches activating. The liquid LPG is pressure fed to a fuel filter/cut off and from there to the converter/vaporiser (you know wot it does). Its then normally passes through an electric stepper motor and onto a manual mixer fitted into the induction system. This is normally located after the air box and can be before or after the air flow meeter. Look for an anti-backfire protection system. This can be a metal flap system or a rubber band or re-setting valves/springs fited directly to the manifold. Or a combination of all (Phew)

LPG can be buggy I've had problems with bad electrics, and I have had two cars burning out air flow meeters (ford granadas) only after gas was fitted. You should be able to find out the name of the brain in the system and you can get the system plugged in to a computer and checked (depending on the system). You may want to buy the programme and link it's quite simple if you tinker already.

Check your anti back fire device's for sticking and that all parts of the induction system's are sealed with no cracks or loose pipes. If you have a filter on the main line then check it. Some are paper filter system but most are magnetic.

For a gas system to work properly it needs a good seal round the induction. The lambda sensor and the systems own stepper motor functioning and the back fire devices clear to operate. This is where I got most of the problems and occasionally with air flow meeters. LPG systems can be prone to backfiring. If persistant at low revs it could be a problem with one of the above, so if it is buggy until you get it fixed only use LPG when you are driving and not stop start (ing) until you can get it diagnosed.

You should have an installers certificate and the gas tank itself will have a re-test date usually 10 or 15 years as its a pressurised vessel

Hope this helps

[daktari]

Excellent. Thanks for the info guys. All i got to do now is work out if i really want it.