Hi Folks,

I have just had my 2.6L EFI TS converted to dual fuel, with a venturi system that uses a throttle position sensor and PWM regulation of vapour.

According to the Impco owner's manual, when starting with the fuel switch on the LPG position, the engine starts up with a small amount of petrol then the gas takes over. My installer claims the petrol runs for a fraction of a second.

My installer also advised it is important to turn the key straight to start (gon't click slowly past the On position). Would anyone know why?

When cold, the car initially fires up but then dies after about a second, consistently. I suspect the petrol start is happening like it should, but the LPG hasn't yet been fed to take over. Warm starts are fine. Does anyone know if this is normal? I've heard that this problem sorts itself out after a week, but if there is a way to keep the petrol going for a bit longer, that may solve this dilemma.:confused: What have you experienced?

My forklift at work does a similar thing - unless you warm it up, as soon as you put any load on the motor it'll stall.

Because gas is stored as a liquid, and is run through the gas convertor to change it back to gas, the convertor has to be hot enough to do it's job, which means that the engine coolant also has to be hot enough.

Can you run it on petrol for 5 or so minutes before switching over to gas?

I'd say it's pretty normal. I've got myself an LPG injection system and it's set up the way it will switch from petrol to lpg automatically after engine coolant reaches certain temperature since the heat from the coolant is required to convert lpg from liquid to vapor state. Strange, they didn't use a switch that does the job automatically and didn't tell you should warm the engine up a little bit before switching. BTW. How much is to convert a car in the AUSTRALIA? Say you use mixer system which should be cheaper, i guess.

Id say it needs a LPG tune first.. Have you spoken to the installer..?? How long since you fitted the gas..?? Has it always done this or is it just starting to do it..??

Id say it needs a LPG tune first.. Have you spoken to the installer..?? How long since you fitted the gas..?? Has it always done this or is it just starting to do it..??

I agree completely with what Ego said, it will most likely be fixable with a tune-up and it can take a few goes to get it set to where it should be.

From what my uncle told me (he installed my LPG) the petrol that is used in only a squirt, it doesn't actually run on the petrol. He told me that when the motor is cold it's harder for the LPG to ignite. To overcome this, the system shoots a small quirt of petrol to help ignite quicker.

The reason you need to turn the key on all the way first time round is because if you pause the timing of the petrol and the ignition will be off and it won't ignite. If the timing is wrong, the system needs a couple of seconds to reboot before trying ignition again.

From what I know about my system, all your car needs is a tune up and it should be fine.

I agree completely with what Ego said, it will most likely be fixable with a tune-up and it can take a few goes to get it set to where it should be.

From what my uncle told me (he installed my LPG) the petrol that is used in only a squirt, it doesn't actually run on the petrol. He told me that when the motor is cold it's harder for the LPG to ignite. To overcome this, the system shoots a small quirt of petrol to help ignite quicker.

The reason you need to turn the key on all the way first time round is because if you pause the timing of the petrol and the ignition will be off and it won't ignite. If the timing is wrong, the system needs a couple of seconds to reboot before trying ignition again.

From what I know about my system, all your car needs is a tune up and it should be fine.
Thanks for the info guys. The cold start issue seems to be subsiding, although the mornings are getting warmer at the same time.

It's a fresh conversion, so when it gets its 1000Km inspection and tune, things should be optimal.

Hey Mean Magna, what consumtion rate does yours run at on LPG, and what engine and trnasmission is that with? I'm expecting my first 1000Km to be at around 15l/100Km, then after the tune I would expect 12-13's.

I'm running a 4cyl auto which generally gets around 12L/100km... I think. It's somewhere around there anyway.

It's a fresh conversion, so when it gets its 1000Km inspection and tune, things should be optimal.


Thats ok.. Has it had its 1500km check over.. They are ment to go over everything to make sure there is no leaks. But yeah im only a few thousand ks into a Install too. Had the same issue. Mine is only sum times though. You just need to hold the key in the ON position untill engine starts..

Put the same system on Mums TS 2.6, and it did the same stalling on cold starts. I hear its a simple tune thing they address at the 1000km tune up. Its set overly rich and bit out of whack when new as apparently the converter has to (bed in" (no idea why...).

A few thousand kms and a tune up and it behaves and starts well now.

Dont know about your installer, but have a good look at all the new pipes and hoses in the engine bay - I had them reroute a few as they were rubbing through on the manifold....

Its set overly rich and bit out of whack when new as apparently the converter has to (bed in" (no idea why...).
Apart from the need to check for any leaks, the 1000k check is for the benefit of the converter. There is a diaphragm in there, it stretches as the vehicle is used and after 1000 to 1500 it is generally considered stretched as far as its going to. This of course varies the mixture constantly as the vehicle is used and all the settings should be checked on the first service as well as looking for leaks and rubbing of hoses.

I have the doughnut tank installed and as it only holds 52ltr usable, I feel like I am always filling it, but in reality, road trips are very consistent at 500k to 540k ltr to the tank at 95 to 100km/h and metro driving for me is 370k to 400k. My metro is down a bit as I commute from work in Adelaide up and down the freeway from Mt Barker in the Adelaide hills. That road is just not good for any sort of economy, but its still good :)

Apart from the need to check for any leaks, the 1000k check is for the benefit of the converter. There is a diaphragm in there, it stretches as the vehicle is used and after 1000 to 1500 it is generally considered stretched as far as its going to. This of course varies the mixture constantly as the vehicle is used and all the settings should be checked on the first service as well as looking for leaks and rubbing of hoses.

I have the doughnut tank installed and as it only holds 52ltr usable, I feel like I am always filling it, but in reality, road trips are very consistent at 500k to 540k ltr to the tank at 95 to 100km/h and metro driving for me is 370k to 400k. My metro is down a bit as I commute from work in Adelaide up and down the freeway from Mt Barker in the Adelaide hills. That road is just not good for any sort of economy, but its still good :)
Thanks for the info on the diaphragm.
I also noticed a clicking sound inside the converter, when the coolant has not yet reached operating temp. Is this normal?
I'm also wondering how to adjust the starting petrol squirt eg duration / mixture. The squirt always succeeds in initially starting the engine, but then the revs momentarily dip after about half a second, and it often stalls at this point. Any other ideas?

Thanks for the info on the diaphragm.
I also noticed a clicking sound inside the converter, when the coolant has not yet reached operating temp. Is this normal?
I'm also wondering how to adjust the starting petrol squirt eg duration / mixture. The squirt always succeeds in initially starting the engine, but then the revs momentarily dip after about half a second, and it often stalls at this point. Any other ideas?

An update - the installer now has on back-order a "vapour-lock" - a device to stop the vapour in between the converter and the venturi, from dissipating.
Meanwhile, the workaround is to depress the accelerator a little as soon as the petrol fires up the engine (no accelerator during the cranking of course)

I'm not the only 1 who put my 4cyl ts onto gas??? Awesome, my mates say im an idiot but its a freaking 2.6L...:)
Um, well on cold starts mine will kick then stall, unless i feed it just after it starts then its all good... DO NOT Feed before or during turning over, it WILL backfire, trust me... lol. If yours is too bad for that then definitely get a tuneup, i think u are supposed to get that done after a while, I never did tho cos I'm happy with it and its a fair drive to my gas guy and i cant be stuffed organising to leave it with them and get home etc.

I'm not the only 1 who put my 4cyl ts onto gas??? Awesome, my mates say im an idiot but its a freaking 2.6L...:)
Um, well on cold starts mine will kick then stall, unless i feed it just after it starts then its all good... DO NOT Feed before or during turning over, it WILL backfire, trust me... lol. If yours is too bad for that then definitely get a tuneup, i think u are supposed to get that done after a while, I never did tho cos I'm happy with it and its a fair drive to my gas guy and i cant be stuffed organising to leave it with them and get home etc.
Yeah, we know to not depress the accelerator until after the initial start-up. We need to hold it down for about 2 more seconds while the Check Engine light flickers, then she settles down fine.
I am looking forward to getting this Vapour-lock installed.
As my out-of-pocket for installing this technology was only $600, the break-even point will be before Eatster 2009.

I have noticed the pull of the engine increases at higher RPM, so I might advance the static timing a little so she doesn't ping on ULP, but will get a more efficient burn in the rev range I normally drive in. I normally accelerate briskly but change up by 3000rpm. If then the take-offs have a problem at lower rpm, I can block the vacuum advance and compare (LPG has a flatter igntion advance vs rpm curve but needs more advanced stactic timing optimally).