LPG Discussion Forum

I'm hoping for a little advice on an issue I have with my car. It's a 1996 XJ6 (3.2 straight 6) and it is fitted with a Stefanelli multipoint system. I'm a novice when it comes to LPG and have an issue with my system that I'm hoping someone can help with. The car runs perfectly on petrol but when on LPG, if I use more than about 20% throttle it is likely to trip out and switch back to petrol. It's usually worse under load and when the auto box changes it is likely to flick off as well. If I drive steady then I can easily get up to 70+ mph and it's smooth as silk but it is very difficult to not use more than 20% throttle.

My vapouriser is covered with a piece of shiny bubble wrap! The first thing I did was remove this but it made a dramatic difference to the warm up time (it was taking >10 minutes to switch to LPG). With this in place it switches over as soon as the car is up to temperature. I have highlighted 4 bolts which protrude from the vapouriser, should I touch any of this stuff?

What is the part in picture 3, it looks like some sort of accumulator?

Is it OK for the LPG injectors to fire into the inlet manifold via a piece of rubber hose as shown in the 4th picture? Does this not screw up the spray pattern?

Where would I find a filter in the system?

Any ideas or feedback is welcome!

James

Sounds like the sort of issues you get with clagged filters, which may not have been changed in ... how long?

The gas injectors inject gas, there is no spray.

rossko wrote:Sounds like the sort of issues you get with clagged filters, which may not have been changed in ... how long?

The gas injectors inject gas, there is no spray.

Thanks for the quick reply, where would I find the filters?

Not sure what you mean by there is no spray? Is it different to a standard fuel injector?

jseaman wrote:Where would I find a filter in the system?

Where ever the fitter put them, every system is fitted differently, you will have to trace your gas pipe work and find them that way.

You should have a vapour filter on the hose going to the injector rail and a liquid filter, this is mostly bolted on to the vap, but could be a separate solenoid and liquid filter combined, you could also have both of them fitted!

jseaman wrote:Not sure what you mean by there is no spray? Is it different to a standard fuel injector?

It's injecting gas not a liquid, so there is no pattern, as the gas mixes with the air in the manifold/cylinder.

Thanks, I appreciate they're all different but if you could give a little detail on what they look like? Is it like a fuel filter? Do I have to buy specific Stefanelli ones?

I see what you mean - so there's no problem having a tube between the injector and manifold then?

jseaman wrote:I'm hoping for a little advice on an issue I have with my car. It's a 1996 XJ6 (3.2 straight 6) and it is fitted with a Stefanelli multipoint system. I'm a novice when it comes to LPG and have an issue with my system that I'm hoping someone can help with. The car runs perfectly on petrol but when on LPG, if I use more than about 20% throttle it is likely to trip out and switch back to petrol. It's usually worse under load and when the auto box changes it is likely to flick off as well. If I drive steady then I can easily get up to 70+ mph and it's smooth as silk but it is very difficult to not use more than 20% throttle.

There is a restriction in the gas flow so the pressure drops under high demand and it changes back to petrol.

jseaman wrote:My vapouriser is covered with a piece of shiny bubble wrap! The first thing I did was remove this but it made a dramatic difference to the warm up time (it was taking >10 minutes to switch to LPG). With this in place it switches over as soon as the car is up to temperature. I have highlighted 4 bolts which protrude from the vapouriser, should I touch any of this stuff?

The bubble wrap has been put there as some sort of insulation either to compensate for poor coolant flow (to make it warm up quicker) or to protect it from excess heat (which shouldn't be a problem as it needs to be nice and hot). You don't make it clear whether it changes over earlier with or without it, but leave it in the state where it changes over quickest.

The three bolts on the vapouriser itself should not be touched but the one furthest to the left on your picture is the liquid phase filter and front shut off solenoid. This is almost certainly the cause of your restriction and needs cleaning/replacing. With the system switched off, slacken the input pipe union to this unit slightly to release gas pressure in the pipe running from the tank. Liquid gas will escape for a while, quite a while as you can have up to half a litre of liquid in the pipe which will make about 125 litres of gas vapour. Do it outside in the open and not over any drains (as the gas is heavier than air and will pool in them), preferably on a windy day to diperse the vapour. Then you can undo the bolt and take the filter element out. Make sure you tighten the input union again before you try to run on gas again.

jseaman wrote:What is the part in picture 3, it looks like some sort of accumulator?

If it is in the hose from the vapouriser to the injectors, it is the gas phase filter. Clean/replace. This is much less likely to be the cause of your problems.

jseaman wrote:Is it OK for the LPG injectors to fire into the inlet manifold via a piece of rubber hose as shown in the 4th picture? Does this not screw up the spray pattern?

As Ross and Simon said, it's a gas, it doesn't have a spray pattern. Remote injectors and hose is normal.

jseaman wrote:Where would I find a filter in the system?

You already have......

jseaman wrote:Do I have to buy specific Stefanelli ones?

Was going to make a funny comment, but i'll be good.....

Vapour filter, you can buy a generic one, prob will be 12mm, the liquid one will be specific to the vap so you have to buy the correct one for it yes.

If you don't know what your doing tho, i'd suggest taking it to someone to service it for you, it won't be that expensive for them to do it and sort your problems out.

Si, if you look at his second picture down, you can see the liquid phase filter in the shut off solenoid. It looks identical to the one I had on my old Saab and Tinley Tech supplied me with a filter for that off the shelf.

Take it to someone? Where's the fun in that?

Gilbertd - Thanks for the detailed response, that's exactly what I needed. I figured it would be a pressure drop of some kind nut just didn't know why.

Sorry, the changeover is quicker with the bubble wrap fitted so it is insulating it.

"With the system switched off"
Does this mean I have to close off some kind of vale on the tank?

Any ideas on a filter supplier? I'd like to do both at the same time if I can.

sijones - also thanks for the input. Although I don't know LPG stuff at all I am more than capable with a set of spanners and can't possibly bring myself to use a garage


If you don't mind giving me a bit of noob advice, how does the filtration system normally work i.e. why a vapour and liquid filter. Does it filter the liquid for a certain particulate then pass through the vapouriser before filtering the gas for something else?

Oh, and for clarity this is the likely problem part:

That's the boy. They have a liquid phase filter (that one) to collect 'heavy ends' which are a lubricant in the liquid gas that is added to lubricate the pumps. You may well find that it is partially full of a waxy, smelly gloop. Tinley Tech (www.tinleytech.co.uk) should be able to provide you with a filter element but you may need to take it out and get the dimensions. Alternatively there are a number of suppliers on eBay.

The vapour filter is there to stop any fine particles getting through that could damage or clog the injectors. If the liquid phase filter is doing it's job though, it shouldn't have a lot in it and is far less important than the liquid phase filter.

By switching off the system I mean just that. With ignition off, or if you are really paranoid, the battery disconnected, the tank solenoid valve will be closed so no gas will flow. You may also have a manual shut off on the tank, if so, close that off too. To lessen the amount of gas in the pipe, if you close the manual valve, or disconnect the wires from the tank shut off solenoid and then run the car at idle on gas, it should use up a lot of what is in the pipe. There'll still be some in there but not as much.

Gilbertd wrote:Si, if you look at his second picture down

I would but am in work and they block all photo's... thankfully am leaving end of month for a new job where at least i will be able to see pictures on the web!

Gilbertd wrote:Take it to someone? Where's the fun in that?

Better than him killing himself, am a playing the safe than sorry card on this one!

jseaman wrote:sijones - also thanks for the input. Although I don't know LPG stuff at all I am more than capable with a set of spanners and can't possibly bring myself to use a garage

I don't go a garage for anything either to be fair, and depending on your ambitions it may or not be worth getting the lead for it... If after changing the filters it underperforms and needs to be plugged in to re turn it then you down the route of getting a cable etc...

So sometimes, biting the bullet and paying for a service will get the filters and it tuned to be running right all done with no hassle.... ish...

Seeem to have lost my earlier reply - thanks gilbertd again for the info. I will do an exploratory removal and see what's what.

I will check out the tank (and probably post a pic to be sure) to identify if there's a shut off valve. I like the idea of using the gas at idle and not spilling it all over the place!

sijones - good luck with the new job Don't worry, if I kill myself I promise not to post any abusive replies on here.

I did contact the only LPG place I know around here and they refused to work on it (only do prins systems now), I also tried the original supplier who appears to have just shut it doors this week!

I am no stranger to mechanics (just bought my third kit car yesterday and have my Supra in bits which is a minimum 400bhp when I strap the T4 and 550cc injectors on after I build a forged bottom end in the next month or two) but just need the help on the bits I don't know which is where this forum is proving to be invaluable so thanks to all

The liquid phase filter is just a standard valtek element type. Any LPG converter should have one on the shelf. If you want to diagnose that it is the problem then you can just take it out and see. But don't leave it out for long as you will have clogged up injectors.

Tubbs wrote:The liquid phase filter is just a standard valtek element type. Any LPG converter should have one on the shelf. If you want to diagnose that it is the problem then you can just take it out and see. But don't leave it out for long as you will have clogged up injectors.

Thanks again, I appreciate all the responses.

I'll remove it, try my local LPG guy (who didn't want to work on it!), and failing that I'll at least have the measurements. It won't be off for more than a few hours because I use the car daily

When you take the cover off, make sure you don't lose the O ring seal around the edge.

I had a few minutes this morning to take some more pictures for you:

This is the set up in the boot:



I guess I just turn this small adjuster screw with 'OFF' next to it to shut off the supply:



The vapour filter looks like it just screws off, is that correct?



Then disconnect the line at the bottom of the liquid filter - I assume this is a flared hard line like a brake pipe?



Do you then take the fitler off completely from here to clean/replace?



I don't know if these can help with identifying a suitable filter:

Is it worth grabbing these 2 beforehand in case I get lucky and they fit?

http://www.ebay.co.uk/itm/OMVL-DREAM-XX ... 4ab63fc2fe

http://www.ebay.co.uk/itm/LOVATO-LIQUID ... 4ab63fc2f9