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[D]

Profess are well known for being very average to poor with their install quality. They are also well known to randomly change components and charge exorbitant rates. I would stay away as LD suggests.

I can suggest someone in Tenbury wells who is very good and much more reasonably priced. Also very well regarded on the LPG forum. Still not that close mind.

[berserkerboy]

Tenbury Wells is about 2hrs from us. Please let me have the contact in case I need to use them. Thanks

[zirk]

I've said it before and I'll say it again... Don't use Profess Autogas

You need to get it to someone who knows what they're doing but I agree it sounds like temp sensor. If they fitted the LPG I'm pretty confident the coolant feed to the vap will be wrong 

My car switches over to gas within 200yds of leaving home. I've always thought this to be too quick, although I get warm air within about a mile.

Just for giggles, turn the heater on full hot next time you go out for a drive and see if it switches to LPG ok

I took a look at the 2 vapouriser coolant connections yesterday. One of the pipes disappears to the rear of the engine and is presumably tapped into the HBV. The other pipe comes up and is tapped into the pipe coming from the coolant header tank. Would that be correct connections?
I emailed Profess LPG yesterday complaining that the switch back to petrol would not be caused by the faulty injectors, if indeed they are?, but that the fault was more likely to be one of the ones suggested in this thread. They just replied that they couldn't comment until the car had been seen by their factory trained technician....It just has been! Have cancelled the replacement of the injectors with them.
Regarding your suggestion of driving away with the heater on full. Presumably we would expect the car to not switch to LPG as there would not be enough heat to the vap?

Injectors wont throw it back to petrol, Injected Solenoids will though, ie, if you unplug one when running on LPG it will throw a fault and switch back, sometimes the Solenoids and wiring are mounted too high above the engine, causing it rub or vibrated with the bonnet clothe which can cause intermittent issues, worth a check.

[Lazydocker]

I've said it before and I'll say it again... Don't use Profess Autogas

You need to get it to someone who knows what they're doing but I agree it sounds like temp sensor. If they fitted the LPG I'm pretty confident the coolant feed to the vap will be wrong 

My car switches over to gas within 200yds of leaving home. I've always thought this to be too quick, although I get warm air within about a mile.

Just for giggles, turn the heater on full hot next time you go out for a drive and see if it switches to LPG ok

I took a look at the 2 vapouriser coolant connections yesterday. One of the pipes disappears to the rear of the engine and is presumably tapped into the HBV. The other pipe comes up and is tapped into the pipe coming from the coolant header tank. Would that be correct connections?
I emailed Profess LPG yesterday complaining that the switch back to petrol would not be caused by the faulty injectors, if indeed they are?, but that the fault was more likely to be one of the ones suggested in this thread. They just replied that they couldn't comment until the car had been seen by their factory trained technician....It just has been! Have cancelled the replacement of the injectors with them.
Regarding your suggestion of driving away with the heater on full. Presumably we would expect the car to not switch to LPG as there would not be enough heat to the vap?

Suggested it because you said it was working fine... Just wondering if they have connected to the wrong pipe at the HBV

Oh... And not really is the answer to the correct connections question. In theory yes, but our experience says otherwise

[berserkerboy]

Car stalled immediately when I tried to move off with heaters on full from cold. Obviously it's trying to switch in too early as it's fine on petrol.
When car is warm I can switch over manually okay. But there is this intermittent problem of switching back to petrol. So maybe Profess are right about the faulty gas injectors.

Can I get the injectors recommended on this thread and install myself without the need for a diagnostics setup. Presumably the injectors work by opening for a fraction of a second so I am not changing any parameters by swapping over to injectors that are working properly. I will not change over the nozzles that determine the actual amount of gas going into the cylinders, or are these likely to be worn out?

[Viral_Jim]

Car stalled immediately when I tried to move off with heaters on full from cold. Obviously it's trying to switch in too early as it's fine on petrol.

This would seem to support the idea that the problem lies with how the heater pipes have been connected rather than your injectors. I would guess the "intermittent switching back" could be down to when the thermostat opens and closes. Could be wrong though.

There are some VERY detailed guides on LPG installation in the Maintenance Guides section. I would have a look through those for how the hot water pipes should be connected. If yours don't match I would suggest you change them so they do  . It might also be with checking the exact spec of the kit you have. Ie what injectors, vaporiser etc. If they are "on the edge" in terms of their BHP capacity vs the BHP of the car, that also won't help.

[Marks DTM Calib]

The description of the heater pipes tells me there plumbed wrong, I suspect they fitted a T piece at the rear and then routed through to the return hose on the header tank.

I would put money on this being the route cause and suspect they set the cut over temp low to bodge around the faulty install.

[Kevin Wood]

Yep, sounds like it to me.

The coolant flow through the vapouriser is to replace the heat that the gas absorbs in becoming a vapour. My car will happily run on LPG from stone cold - the coolant doesn't need to be hot (although it's better practice to set the switchover temperature high to avoid excessive heavy ends getting deposited).

What I am saying is that a healthy flow of stone cold coolant will keep the vapouriser working. It just needs to be prevented from dropping close to the -40 degrees C that the propane boils at. The fact that it's stalling and switching back tells me that it doesn't have adequate coolant flow.

Coolant needs to be sourced from the heater circuit, before the heater bypass valve, which can cut off the flow in some circumstances. The typical bodger will connect it to the throttle body coolant feed, which only gets a dribble of coolant, and only then when the engine is fully warmed up, or they'll connect it to the heater matrix pipes without bothering to delve further and find that the HBV can cut off this coolant flow.

[berserkerboy]

Looks like a job for the weekend, dismantling to see exactly what is going on at the HBV. Think I'll download the stag software and put on my old laptop. Cheapest ECU interface adapter I can find is £19.99. Then I can see what they have set the changeover temperature at.

[Kevin Wood]

Yep. If you can, post a photo of the coolant line routing to and from the vapouriser and we'll take a look.

[berserkerboy]

Okay. Will try to do so.

[T.m.f]

When you 1st connect laptop to stag ecu,do not update the firmware,when you get to the screen for settings and see the save button,save it so as you have the original lpg map and settings,because if you do a furmware update 1st you may not save the original lpg map etc.

[berserkerboy]

Okay

[Lazydocker]

We know the Stag setup well here so plenty of help available

Because we know the flow rate is high enough, most of us route all of the coolant from before the HBV through the vapouriser and back into it. However, if the flow rate is insufficient then a T would need to be used. I've yet to find a Vap that wouldn't flow enough

[Marks DTM Calib]

The flow restriction of the vaporiser will be less than the valve in the bypass valve so no issues affecting the coolant flow to the matrix.