LPG cold starts

darth sidious

darth sidious

New Member
One for the LPG experts/fans.

According to http://www.flogas.co.uk/autogas/faq/

Oil and filter life can be doubled as LPG leaves less deposits in the combustion process than petrol / diesel, thus reducing the chances of oil contamination. Cylinder and piston wear is reduced because LPG mixes better with the air during cold starts as it enters the chamber as a gas, as opposed to diesel and petrol, which enter as a liquid.
Click to expand...

I was always under the impression cold-starting on LPG was a big no-no and asking for trouble. (LPG has a refrigerating effect as it vapourises [I think that's the correct UK spelling!], causing some component(s) to stick if the engine is cold [or something like that!])

Any ideas, chaps?
 
First off, the Rover V8 is a very old engine design -into service 1962 in the US - so the same rules don't apply on oil changes. Anything over 3,000 mls and you are asking for accelerated engine wear. And always use a "Classic" 20W/50. The key point being that they have ZDDP in them which modern oils do not (ruins catalysts). Castrol and Millers are two suitable brands but there are others.

As to cold starting on LPG. Well will it? Most conversions on the V8 give you the option to start on petrol and then switch over to LPG. This is because most LPG systems don't have an equivalent to the choke. If it will cold start on LPG then you shouldn't have a problem. Your comment on gas mixing is correct. There is an outside possibility of problems if you have one of the very latest and very expensive direct injection LPG systems where there is an individual injector for each cylinder, but these are rare even for the V8.

Chris
 
chrisyork said:
First off, the Rover V8 is a very old engine design -into service 1962 in the US - so the same rules don't apply on oil changes. Anything over 3,000 mls and you are asking for accelerated engine wear. And always use a "Classic" 20W/50. The key point being that they have ZDDP in them which modern oils do not (ruins catalysts). Castrol and Millers are two suitable brands but there are others.

As to cold starting on LPG. Well will it? Most conversions on the V8 give you the option to start on petrol and then switch over to LPG. This is because most LPG systems don't have an equivalent to the choke. If it will cold start on LPG then you shouldn't have a problem. Your comment on gas mixing is correct. There is an outside possibility of problems if you have one of the very latest and very expensive direct injection LPG systems where there is an individual injector for each cylinder, but these are rare even for the V8.

Chris
Click to expand...

I think you're on the money there Chris. My BMW 328 has the current Prinz system, which starts automatically on petrol, then switches to gas after about 90 seconds. It's superb generally and means my car does the equivelent of 50+ mpg at almost all times. I'm sure the reason for petrol starting is exactly as above.

Cheers
Nick
 
My father had a Bedford CF campervan some years ago, fitted with a Holden 6 cylinder and dual fuel LPG/Petrol. He almost never used the petrol and to start it on LPG, all you had to do was press the changeover knob for a couple of seconds which would sent a brief blast of LPG down the carb. This was an old and crude system, probably fitted in the mid '80s that had a small alloy ring fitted between the carb and air cleaner with a pipe to the gas mixer, but I don't recall any problem with cold starts. Just give it a longer squirt. (Although NZ 'cold' is not quite as serious as UK 'cold')
 
My Audi had the 2.7L V6 twin turbo and runs on LPG, but it will NOT start on LPG.

I am told that this more to do with the system fitted than the engines inability to do so, and there is a way of overriding it if you run out of petrol (don't know what it is though :oops: )

Apparently, the system fitted to carburettor vehicles (Like Spakry) can start on LPG with no problem at all. I did meet a chap in Bridport who had a 3.5L range Rover running on LPG and he had actually removed the whole petrol system including the tank.

If you do start it and run it on solely on LPG just be aware that petrol these day has a very short self life, and can go stagnant in your tank if you keep it there for a length of time.

Also be aware that this fun loving caring government have increased the tax on LPG greatly over the last few months so it may be as much as petrol soon if we don't get rid of the thiev&%^ B$%*SDS

Richard
 
quattro said:
My Audi had the 2.7L V6 twin turbo and runs on LPG, but it will NOT start on LPG.

I am told that this more to do with the system fitted than the engines inability to do so, and there is a way of overriding it if you run out of petrol (don't know what it is though :oops: )
Click to expand...


My Prinz system can be over-ridden to start on LPG. I've never done it though.

quattro said:
Apparently, the system fitted to carburettor vehicles (Like Spakry) can start on LPG with no problem at all. I did meet a chap in Bridport who had a 3.5L range Rover running on LPG and he had actually removed the whole petrol system including the tank.

If you do start it and run it on solely on LPG just be aware that petrol these day has a very short self life, and can go stagnant in your tank if you keep it there for a length of time.

Also be aware that this fun loving caring government have increased the tax on LPG greatly over the last few months so it may be as much as petrol soon if we don't get rid of the thiev&%^ B$%*SDS

Richard
Click to expand...

There were assurances given by the aforementioned thieving b*stards a year or so ago that taxes on LPG (being a 'green' fuel) would be held for five years...not sure if this has actually happened. It has now creeped to 62.9 a litre at the motorways pumps down here. That's a 10p increase roughly since the middle of last year.

Lowest I've paid is the wonderful 49p a litre at the LPG specialists in Wolverhampton. Love 'em.
 
Thank you guys!

I meant in general on any car (new, used, classic, etc), not specifically those wonderful cars we call P6 Rovers :)P) (The Lounge here is OK for non P6 matters, isn't it?)

I know the ZDDP requirement for classic cars (read about it here some months ago!). Millers, Castrol and Penrite do indeed sell suitable oils for the wonderful pieces of machinery we all love, and how paramount it is to change the oil every 3000-4000 miles. I was more pondering about the cold start angle!

I actually found where I had seen the "don't start on LPG" :- http://www.go-lpg.co.uk/Do_I.html

This from that site
Vaporiser freezing

If you have an LPG system that will allow you to select LPG only (including cold starting) this can be asking for trouble, especially on damp days or during the winter months (or both). The vaporiser may freeze up in seconds if it is not being heated by engine coolant. It is much better to start on Petrol, avoiding any vaporiser icing problems. Switch over to LPG when the engine is fully up to temp. Stick to this and avoid a lot of potential problems! (This effect is more fully described in the item 'Will there be any difference in performance after conversion')

If you start up from cold on gas, the vaporiser is not being heated by engine coolant. There is a refrigerating effect as the gas within it vapourises. It will freeze up and stick, possibly causing weak mixture backfiring or gas leakage. If you run the engine up to temp. on petrol before switching over to gas this cannot occur as the engine coolant will already be hot. Don't be fooled into thinking that the air is too warm for freezing to occur, outside temperatures do not have to be down to freezing level for this to happen. The vapouriser may freeze at temperatures up to + 25 degrees Centigrade, especially if the air is very damp..
Click to expand...
Click to expand...


I know classics (including P6's) don't usually have injectors (well, unless someone has mod'ed the engine!), but surely there is a vapouriser even on carb'd engines?


To be honest, the information being spat around about LPG seems contradictory between sources and various "experts"! :-S

Also be aware that this fun loving caring government have increased the tax on LPG greatly over the last few months so it may be as much as petrol soon if we don't get rid of the thiev&%^ B$%*SDS
Click to expand...

Oh, definitely the powers that be will increase the tax on LPG. In fact, I'm certain that one day they will 'suddenly' discover it's just as polluting as petrol/diesel, AND/OR 'suddenly' discover it has other dangerous chemicals as a result of being used as a fuel, so the congestion charge rebate will be stopped and even more tax levied! It echo's the Unleaded thing some 15 or so years back!
 
I used to run a V8 P6 on Gas and it always started on it no problem with Petrol only being used when I ran out of Gas :)
 
GrimV8 said:
I used to run a V8 P6 on Gas and it always started on it no problem with Petrol only being used when I ran out of Gas :)
Click to expand...

Oh I see!

To be fair I think the people here have latched onto being specific about LPG on a P6, whereas I was asking about cars in general (i.e modern cars with modern fuel injection, control systems etc), not just classic cars.

Just found it odd that one source (well, a supplier of LPG, so has a vested interest!) was fetting how better starting from cold on LPG was, while another source (an LPG installer, who has <more-or-less> the same vested interest as the LPG supplier!) said it's not recommended at all!

Perplexing to us mere mortals!
 
Is that why some LPG converted cars backfire and set fire to the air filter assembly ? Or that's what used to happen
 
Most ironic thing about LPG IMHO is that a lot of modern cars cannot safely run on it without an additive...

Modern Range Rovers and other cars you'd expect to be really good on gas have to have the LPG version of lead additive put in via a filter. Simon just converted a Mercedes taxi that had to have just this. My BMW is fine on LPG, as indeed would be my Honda engined Rover 827 Coupe, if I went that route.
 
NickDunning said:
Most ironic thing about LPG IMHO is that a lot of modern cars cannot safely run on it without an additive...

Modern Range Rovers and other cars you'd expect to be really good on gas have to have the LPG version of lead additive put in via a filter.
Click to expand...

That's a very good point! I wonder if GrimV8 had to add an additive with his LPG'd P6? Or even the brown LPG'd P6 featured in the Jan 2008 edition of Practically Crappy... er... sorry... I mean Practical Classics, of course!
 
DaveHerns wrote:
Is that why some LPG converted cars backfire and set fire to the air filter assembly ? Or that's what used to happen

Cor blimey, I never heard of that!
Click to expand...

As the following piccie will testify, it can most certainly happen, although the this happened just after it had run out of LPG and gone back to petrol.........

16022007001.jpg


Just on the way back from the cash & carry with the wife and little'un :shock:

Needless to say, a write-off :(
 
norsewood said:
As the following piccie will testify, it can most certainly happen, although the this happened just after it had run out of LPG and gone back to petrol.........

Just on the way back from the cash & carry with the wife and little'un :shock:

Needless to say, a write-off :(
Click to expand...

Ooh, that is nasty! :(
 
darth sidious said:
NickDunning said:
Most ironic thing about LPG IMHO is that a lot of modern cars cannot safely run on it without an additive...

Modern Range Rovers and other cars you'd expect to be really good on gas have to have the LPG version of lead additive put in via a filter.
Click to expand...

That's a very good point! I wonder if GrimV8 had to add an additive with his LPG'd P6? Or even the brown LPG'd P6 featured in the Jan 2008 edition of Practically Crappy... er... sorry... I mean Practical Classics, of course!
Click to expand...

I never knew of such an additive TBH :oops: I bought the car ( a real dog on Ebay ) several years back purely for the Gas kit but ran it for about two years daily before it had to be scrapped. The engine was a real gem ( which I sold on )never used oil to excess, pulled well, not sure what it looked like inside though :)
 
darth sidious said:
NickDunning said:
Most ironic thing about LPG IMHO is that a lot of modern cars cannot safely run on it without an additive...

Modern Range Rovers and other cars you'd expect to be really good on gas have to have the LPG version of lead additive put in via a filter.
Click to expand...

That's a very good point! I wonder if GrimV8 had to add an additive with his LPG'd P6? Or even the brown LPG'd P6 featured in the Jan 2008 edition of Practically Crappy... er... sorry... I mean Practical Classics, of course!
Click to expand...

Be interesting to see how you get an addittive into the tank :shock:
 
A friend of mine has a 4.'something' litre Jeep which has a LPG conversion, which will not start on LPG only on Petrol. So I presumme starting on LPG in the cold would definitely not work in this case. The car once running switch's over automatically from petrol to LPG after it has warmed to a certain temp.

My own experince with LPG is on forklift trucks which use LPG only. In winter and in extreme cold, we used to tip a kettle of boiling water over the vapouriser before attempting to start because otherwise the 'well used' engines wouldn't kick up at all, the liquid wouldn't turn to vapour quick enough and would act as a refrigerant. When very cold, they also used a very large amount of gas for the first five minutes while they warmed up. In fact so much so, that once we got them started, we used to move them outside of the building we worked in, because the gas vapours which went straight through the engine and into the outside enviroment. Not very safe when indoors.

During my time in distribution network hubs where we had upto 40 FLT's, I witness two engine fires due to LPG in 13 years. First one was due to a flex supply pipe pipe splitting in the engine bay, probably due to vibration.
The second occured as the truck was about to run out of gas and it backfired. It set alight to the sound deadening material. However, I must add though, that the truck was working and was warm/hot not cold.
 
Some good pieces of knowledge and experience there, Mark!

The impression I get is that LPG has some quirks and traps for the unwary.

I also wonder where the (lead substitute) additive/lubricant would be added to the fuel line.

Maybe GrimV8's engine was one of those that could run on lead-less fuel (for some period of time, at least!)

Thanks guys. Been a good response to my original question!
 
You must log in or register to reply here.
Back
Top