JohnLRV8

New Member
Just wondered because i was told that it has to always start on petrol, but now after correct set up from an LPG mechanic starts up great....
 
Mine won't start, it has to get up to temp before it automatically switches.

I have thought about trying to change it but its not worth the effort IMO as its only a few minutes on petrol before swapping to LPG
 
Mine swaps over almost instantly from start up although it sometimes stalls it probably wants servicing/seing too.
Its usually lumpy when it changes over but soon gets going. Its tempromental lol.
 
How to ruin a petrol engine - chapter 1.

Always start your engine on LPG - the lack of lubricants in the gas will accelerate the wear processes so you can look forward to a costly rebuild much earlier than would normally be the case.

A further advantage is that before the evaporator has warmed up - via the engine coolant - you are very likely to experience a catastrophic backfire, which means you will be able treat yourself to a nice new plenum, elbow, airflow meter and air filter box.

wonderful
 
How to ruin a petrol engine - chapter 1.

Always start your engine on LPG - the lack of lubricants in the gas will accelerate the wear processes so you can look forward to a costly rebuild much earlier than would normally be the case.

A further advantage is that before the evaporator has warmed up - via the engine coolant - you are very likely to experience a catastrophic backfire, which means you will be able treat yourself to a nice new plenum, elbow, airflow meter and air filter box.

wonderful

My old 3.5 110 would start on LPG all summer and I never experienced a backfire the 12 months or so that I drove it.
If your LPG and ignition is set properly then you dont get a backfire.
The only parts not lubricated by the petrol on my V8 were the carbs and the needle valves would sometmes stick.
 
I had a 97 disco with single point lpg, Only time it backfired was when i let it run out of lpg...Only needed to start it once on lpg when the fuel pump gave up the ghost and it was fine.
 
Our D2 will start on LPG if you hold the LPG/Petrol switch over to LPG before start-up, otherwise it goes through the warm-up sequence on petrol.

In the winter, it will start on LPG but doesn't really like it.

Once warm it will readily restart on LPG and saves a fair bit of petrol/money too.

Note that parallel-connected vapourisers take much long to warm up than those connected in series with the heater.

Engine outlet - vapouriser - heater - engine bottom hose.

Slows the heater warm up slightly, but you can be on LPG much quicker this way.

Peter
 
How to ruin a petrol engine - chapter 1.

Always start your engine on LPG - the lack of lubricants in the gas will accelerate the wear processes so you can look forward to a costly rebuild much earlier than would normally be the case.

A further advantage is that before the evaporator has warmed up - via the engine coolant - you are very likely to experience a catastrophic backfire, which means you will be able treat yourself to a nice new plenum, elbow, airflow meter and air filter box.

wonderful
if you can get away with it starting on gas is far LESS damaging than starting with petrol....petrol doesn't lubricate anything,it strips all the oil from the bore thus increasing the wear rate when cold.
 
if you can get away with it starting on gas is far LESS damaging than starting with petrol....petrol doesn't lubricate anything,it strips all the oil from the bore thus increasing the wear rate when cold.

It's not quite as bad as that these days, you're thinking of the days of carburettors and hand chokes.

The Bosch system goes rich for starting, according to the engine temperature, but also weakens as soon as the engine fires up and advances the ignition during the 20-second fast idle period (D2)

If you look at a 100k mileage V8 bore, you'll be surprised how good most of them are.

Oil type and condition have a far greater impact on bore wear these days.

Peter
 
LPG is a dry fuel & doesnt provide the neccesarry lubrication the engine needs on cold starts. It's also good practice to run on petrol every so often to give the injectors a work out.
 
LPG is a dry fuel & doesnt provide the neccesarry lubrication the engine needs on cold starts. It's also good practice to run on petrol every so often to give the injectors a work out.

Petrol doesn't provide lubrication, especially when cold starting, it takes oil off the cylinder walls in excess, but injected cars have a much more controlled system that doesn't need to run the engine on rich mixtures.

What petrol DOES do that LPG doesn't, is provide cooling by virtue of its change from a liquid to a vapour, utitlising the latent heat of evaporation.

LPG already comes into the engine as a vapour, it doesn't bring anything to the party in terms of cooling, and in many cases it is quite warm already.

The engine really couldn't care what comes in, as long as the mixture is a stoichiometric mixture that can be burnt in the combustion chamber.

Starting an already warmed up engine on LPG makes more sense as you are not using expensive petrol unnecessarily and keeping toxic fumes out of the air, and also keeping your exhaust internal corrosion to a minimum.

Peter
 
In the winter time, when the engine is cold I start on petrol and run it for about half a mile then switch over to LPG.

In the summer time, I mostly just start on LPG, I save a fortune in petrol in the summer months.

Although, sometimes the LPG system is a bit lumpy and backfires, blows the airbox appart, I scare people to death when they are walking past, it sounds like a bomb going off lmfao.

Saying that though the LPG system never gets serviced.

John
 
Petrol doesn't provide lubrication, especially when cold starting, it takes oil off the cylinder walls in excess, but injected cars have a much more controlled system that doesn't need to run the engine on rich mixtures.

What petrol DOES do that LPG doesn't, is provide cooling by virtue of its change from a liquid to a vapour, utitlising the latent heat of evaporation.

LPG already comes into the engine as a vapour, it doesn't bring anything to the party in terms of cooling, and in many cases it is quite warm already.

The engine really couldn't care what comes in, as long as the mixture is a stoichiometric mixture that can be burnt in the combustion chamber.

Starting an already warmed up engine on LPG makes more sense as you are not using expensive petrol unnecessarily and keeping toxic fumes out of the air, and also keeping your exhaust internal corrosion to a minimum.

Peter

Thats why i said you should start a cold engine on petrol, & petrol does offer more lubrication needed for cold starts.
 

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