Thread: Starting on LPG when Cold

what type of mixer?

the EA multiport falcon used 225-300 mixer.as they lay on the side the often get stuck.the convertor needs to be in very poor order to give issues.

the tar-propelene can be an issue.

you shouldnt have starting issues for lpg only.my egas cars have been great but a distributor engine is better..

as of late 90's lpg systems had to pass basic emision standards.so its easier to start on petrol for warm up.
full load drive away with cold engine is often a disaster for late model cars.but this has nothing to do with air temp.

for cold weather the landy type convertor is better.
the falcon vialie is a pain after a year or so but is a fit and pass emision modern unit.

Originally Posted by bee utey

Propane liquefies at minus 40C. So there will still be pressure to run at -5C.
<snip>.

But are you factoring in the fact that on a cold -5C morning the metal of the converter may actually be lower than -5C because it acts as a cold storage device and then you add the cooling effect of a jet of fluid (similar to wind chill) combining to reduce the conversion of sufficient gas to start the engine.

I do know that some years ago when studying at Uni and driving a taxi for income. I was allocated a cab that the mechanics hadn't installed the coolant pipes correctly and on cold nights the converter would freeze and the cab would stall momentarily, allowing some liquid to convert to gas and the engine to pick up and run, then the converter froze again and so on.

The same cab didn't have a problem during the day or when it was warm.

the freezing isnt normally an issue when starting.it is when you got to drive off and put a demand on the regulator.
Ive had issues with freezing in the service line from the tank-someone refered to the tank being exposed.if the gas leaks out overnight the sudden rush of liquid causes temperature/pressure issues.with the new lock solinoids on the tank its not unusual to freeze the soliniod plunger or trip the pressure slow release safety valve.

the older falcon is dreadfull when cold due to mechanics fitting cold thermostats or drilling holes.--for some reason people think they need it.the original thermostat had a bypass control that shuts off the water to the heater/convertor when warm.
The newer ford uses the same waxstat as the V8 and that silly plastic ball that falls off-these lucky to last 12months.the heater system in the pre BA and commodore robs the heat needed in the vapouriser.

the AU Egas has a 3/8 hose looped into the bypass,most dual fuel conversions dont plug up the bypass,so in cold weather the water flows through the heater.the fix is that a electric water pump is fitted.the water doesnt need to be hot just circulate.any thing above -40 will work as long as there is circulation.impco are low pressure units so they dont have as much problems as other types.

most lpg units run very hot-ive done testing and found 50c to be OK.
i had a vac emision tree or electric overload switch to turn off the water flow when it got to 50c.

Originally Posted by Lotz-A-Landies

But are you factoring in the fact that on a cold -5C morning the metal of the converter may actually be lower than -5C because it acts as a cold storage device and then you add the cooling effect of a jet of fluid (similar to wind chill) combining to reduce the conversion of sufficient gas to start the engine.

I do know that some years ago when studying at Uni and driving a taxi for income. I was allocated a cab that the mechanics hadn't installed the coolant pipes correctly and on cold nights the converter would freeze and the cab would stall momentarily, allowing some liquid to convert to gas and the engine to pick up and run, then the converter froze again and so on.

The same cab didn't have a problem during the day or when it was warm.

There are vehicles that for various reasons have problems in very cold conditions. As far as the first start goes, the converter mass won't be colder than atmospheric until after the first amount of LPG has vaporised. As Davehoos says, it's wanting power straight away that causes problems. Warming an engine up on fast idle for a couple of minutes is usually ample to allow you to drive off. If this then causes converter freezing you have a problem with not getting enough coolant flow.

are you using the original vac gas lock.this may not be opening as the engine has low manifold vac?



gas only is better than carby dual fuel.
injected petrol with gas is better-i like simple t/body petrol injection and have a small amount of fuel being injected to keep it clean.

replace a few carby over the years that had holes in the casing from the float rattling around and gasket and vacum leaks are common.

I also had set ups that fuel leaked in over time giving a flooded start.mechanical petrol pump often leak into the sump and the vapour is drwn into the engine flooding it.
also warn needle/seat from being always dry.

had problems with old SU carby refusing to move when cold.they have oil for a damper.
I guess that a cd stromberg with old diaphram may give the same problem.If the plunger wont raise up reduced gas is drawn in.a pluger raiser was sold as a fix.ive also seen vac hoses attached to the bell to raise it.the only was this could work is if the venturi vents are restricred.

my original holden days iv seen plenty of modified single barrel strombergs that ran petrol for idle cold start and throttle pump.but no main jet.the gas was drawn in through a spud and controlled by a gas tap [impco/centry regulator] bit hard to do with a single jet engine.japanese nissan carby engines had a electric powervalve that you could turn off.

Originally Posted by bee utey

There are vehicles that for various reasons have problems in very cold conditions. As far as the first start goes, the converter mass won't be colder than atmospheric until after the first amount of LPG has vaporised. As Davehoos says, it's wanting power straight away that causes problems. Warming an engine up on fast idle for a couple of minutes is usually ample to allow you to drive off. If this then causes converter freezing you have a problem with not getting enough coolant flow.

Thanks bee utey. I know that the coolant fittings are to provide heating of the converter, just like some engines have intake manifold heating and I rather suspect that the cab in question had the coolant on the return line of the heater demister after the tap/regulator which was broken.

That said, in our icecream/frozen food distribution company, we used to make dry ice bricks with a device that merely discharged liquid CO2 through a nozzle into a partially enclosed space. IT didn't matter if it was 35C or 5C it worked as well. So would think freezing LPG by discharge through a nozzle into a similar device would work just as well. Don't think I'd like to have a BBQ with the beer being kept cold by some frozen propane bricks though!

On the subject of poorly plumbed coolant hoses, I am currently repairing a 95 D1. The converter tee pieces are fitted to the heater hoses above the DS rocker cover. All OK except there is a heater tap on this model which bypasses the coolant. With tap "off" a short coolant path is opened preventing any meaningful flow through the converter. Needless to say it's being changed.

Unknown to me, mine was plumbed via the heater and it was not until I was taking it for a roadworthy that it started freezing up - it was the tester who pointed out the frozen converter - frost all over it.

Due to ease of access I have a bypass hose with a little tap in it that bypasses the heater. In summer the tap is in a position that bypasses the heater all together, in winter it is closed allowing all coolant to go via the heater (which is on all the time) and at other times the tap is in a position that allows enough coolant to both the converter and heater.

Heat from the heater only works if the fan is on and access to the tap is from outside the vehicle so can be set in an instant if required.

Garry