S8 D2 OMVL LPG Question
 

So the car has just been fully serviced, MOT'd and a complete and full cambelt change done.

Though today I have noticed a strange problem with the LPG (was working perfectly).

http://www.v8dualfuel.com/images/swi...hematic_02.gif

The system when running on LPG should be just on the G (Gas ON) with the Petrol pump out. When warming up the Petrol Pump stays on and the Orange G flashes.

Now all I ever get is the Red Pump on and Orange G flashing, it never flicks onto LPG even when warm. At idle I have seen it change to LPG only to go back to petrol as soon as any revs are introduced.

Now this may be the Thermostat, Filter or Solenoid at fault so I have ordered the cable to plug in and have a chat with it. But I wanted to ask the question at least in case one of you fine ladies and gents have had similar problems?

The system has been filled up with LPG in case that was it, plus if I cannot resolve it will go to the local LPG specialist for a service and fix.

I have done the normal forum searches and OMVL manual reviews but not come to anything that conclusive.

Car drives beautifully I should add +++

Finally anybody know the normal home for the LPG ECU?

I did have an issue with mine a year or so back, but don't recall the light sequence.

The car was up to temp and had switched over to LPG by the time I got onto the open road. When I got up to speed, it gave me the warning buzzer for no LPG and switched back to petrol. I tried switching back to LPG, but it reverted back less than 30 seconds later. It was due for the LPG service soon, so took it up early. Explained the issue to them, and they diagnosed it as a faulty coil pack. They said that the LPG is less tolerant to external issues, and so switches back to petrol.

Having just had work done on the engine, is there a possibility that one of the leads to a coil pack has been knocked. Either that or you now have a faulty coil pack.

Unfortunately I have no idea if you can use VCDS to test the coil packs, and the people who worked on mine said they spotted the fault with whatever software they use on the LPG system.

Wow, an S8 on LPG!

what system do you have?
Vapour injection or liquid injection?

I used to have a vapour ring (venturi constant supply) system on an old Commodore back in the day.
Was thoroughly unimpressed with it from a power perspective (the Commodore had a wheezy 3.3L L6 of ancient low power origin to start with), but it gave great economy! Especially at 12c (6p) per litre at the time (late 90's)!

I've never really considered it since as it always used to drop engine power.
The more modern systems (vapour injection) were less lossy, but with liquid injection comes a whole new ball game with engine power gains thanks to LPG's higher octane finally being fully utilised...

It could be the solenoid on the reducer needs cleaning, there are filters as well that need changing. If the sensor detects a low gas pressure it thinks you've run out of gas and switches back onto petrol. Unless you know what your doing it could be easier to just book it in for a lpg service and tell them your problems.
Good luck Dave

All fixed +++

Spent some time under the bonnet checking all the wires and connectors and it was a broken wire that was going into the Reducer/ Vaporiser. It looks like it linked to a solenoid hence it was not getting the volts to kick into action.

Fixed for now and a new connector ordered so I can repair it properly.

In regard to the car on LPG its OK for long journeys. I get about 200 miles to a tank of LPG that costs £35 or so. Yes its a little down on power and can be sluggish to respond to the throttle but if you are having a proper drive I just switch it back to petrol as needed.

Its a good addition to the car, keeps the costs down on longer journeys and allows me to say I drive a Hyrbid +++

I used to have a 2000 D2 FL S8 on LPG. Was a Prins system and was excelent. The main real difference was in the wallet. Cleaner and hotter burning which is nice. I found power to be only a little down and only when you really booted it, and it would switch back to petrol after a second anyway....Found it did it a little more when the tank was low, so i'm guessing it was a lack of presure/flow.
And one time the LPG filters needed cleaning, which was an easy job.

To be honest with a 4.2L engine, loosing a little top end power is neither here nor there, you can switch on to Petrol if you find a nice B road to blast, but most the time 95% of a 4.2L engine is more than enough ;)

Always starts on Petrol and i'd advise keeping a 1/8+ in the tank as if the petrol runs dry it can fry the petrol pump and petrol is the lubricant. You also tend to drive more in a if there is an LPG station with reasonable prices you top up, rather than letting things get low. Had a 90L tank across the back of the boot, sure it took up space, but the boot is cavenous that you had a normal size boot left anyway.

My d3 A8 4.2 has a wheel well tank and it's about 60L which is a bit small in my mind and things rattle arround in the boot more now!

Thats odd my D3 4.2 petrol with LPG also has a spare wheel well tank and the most I've put into it is 74 litres +++

I agree with Lee about the economy. earlier this year I drove from Dover to Central Germany and back on LPG and used £95 worth on the entire trip!
(must add that LPG is even cheaper in Belgium than the UK at 30 cents a litre!)

Hi There,

The wheel well tanks do vary in size, you can also tweak the float device to give a touch more capacity....Also the rate capacity and what you can fit in them varies as they always underfil to what the tank is specified due to expansion iirc.

Iritatingly my D3 isn't running right on LPG but that's down to an odd missfire issue and that LPG is less forgiving than Petrol!

Lee