Mazda 6 and BRC setup problems (I think)

[alienb4ndit]

I'm new to LPG therefore my question may seem a bit stupid ao please bear with me.

I am a vehicle technician by trade but have never owned or had anything to do with an LPG system (Porsche owners don't tend to opt for LPG!)

My Mazda 6 2.0 2004 reg has a BRC system fitted. I bought the car 2 weeks ago and all seems ok. I filled it full of lpg and have done about 150 miles. The flashing led's on the switch don't tell me the tank level, the first of the 4 lights just constantly flash. There is a gauge on the tank in the spare wheel well whih now indicates about a quarter of a tank so I assume it has used 3/4 of the tank to cover the 150 miles... all good so far!
The petrol gauge has gradually dropped, which I'd expect given that it starts on petrol etc, etc... My potential problem is this....


On tickover when the engine is warm, if I unplug a petrol injector the engine starts to misfire.. if I pull more injectors the engine misfires further. It will continue to run with only 1 petrol injector connected which suggests that the engine is running on LPG but this also means that its running on petrol too?!?! Is this correct?

Surely, if it's switched over to gas then it shouldn't be running on petrol at the same time?

Am I just unaware of how an LPG system works or do I have a problem?

Many thanks

Paul

[LPGC]

I've converted a few Porsche's to LPG, here's one... http://www.lpgforum.co.uk/viewtopic.php ... 85&start=0

Flashing LED's on switch explained here... http://www.lpgforum.co.uk/viewtopic.php ... 08&start=0

What happens if you pull all petrol injector plugs?

Why not try it the other way around, not pulling LPG injector plugs but disconnecting LPG injector to manifold pipes at the LPG injector rail end - If any gas comes out (you'll hear and feel it in pulses) then it is running on gas. Don't forget to plug the vacuum leak at the now open ended injector pipe.

What you're asking is 'Does the engine run on both petrol and LPG (both fuels together) at idle?'.. The answer to that is almost certainly no (not both fuels together), but your install might be set up to idle (below, say, a certain rpm) on petrol. If this is the case, the installer might have set it up like that because they were having a difficult time getting it to idle smoothly on LPG. To achieve a smooth idle on LPG, particularly on some engines (and yours is one), an LPG ECU compatible with petrol ECU fuelling strategy must be used, manifold nozzles must be mounted in the correct position (close to petrol injectors), injector pipe lengths must be short, correct combination of gas pressure and injector nozzle size must be used, the system must be properly calibrated.

For the last couple of years I've serviced a Mazda6 fitted with a KME LPG system, because the owner won't trust other installers he previously used in the area ... Before finding me the owner wasn't impressed with drive-ability on LPG (low power when booting it, engine warning light issues, it was set to idle on petrol and since he spent a lot of time in jams commuting to work so he used a fair bit of petrol idling). He'd lived with those issues for a year, all the time since having the LPG system fitted elsewhere, and in that time he'd take the car back to the original installer several times and then tried taking it to a few other installers in the area, none of them managed to sort it. I found the system to be fitted with an inadequate reducer (partly explaining the lack of top end power) and calibrated very poorly in terms of both pressure and software adjustment (explaining everything else). I fitted a capable reducer and calibrated it properly - Now it idles smoothly on LPG, drive-ability and power on LPG are indistinguishable from petrol, there are no engine warning light or other issues.

Whether or not you have a problem might depend on your point of view - how the car drives on LPG, any warning light issues, and if you consider idling on petrol a problem... If it has intentionally been set to idle on petrol then this might be telling of underlying issues that the original installer couldn't overcome, and there is no telling if similar installers you might visit could fare any better while charging for having a bit of a tinker with it, or if you'd manage better yourself if you bought a cable etc.

What BRC system have you got (there are several!)? On the ECU it will say BRC and then something else such as Sequent/24/MY07/56/Plug&Drive.. ECU's get better towards the end of that list.

Simon

[alienb4ndit]

Thanks for the detailed response Simon.


A few things to mention:

If I unplug all injectors the car stalls... but with just 1 injector plugged it still runs, allbeit lumpy.

With the bonnet open and on tickover I can hear the distinct ticking/tappety noise from the LPG injectors when Iswitch the LPG system on. I can also feel the LPG hoses to inlet manifold pulsing therefore suggesting it is running on gas at tickover (as well as petrol). So..... I thought maybe it's running on a combined fuel on tickover but will switch to pure LPG when revs are increased? So I tried disconnecting the petrol injectors whilst holding the revs at anout 2000rpm.... engine behaves the same, runs lumpy on just 1 petrol injector connected and cuts out when all unplugged.

I've not looked for the ECU, I'll go have a look for it and come back with some numbers

Cheers

[LPGC]

Does it stall immediately or after a second or so? What year Mazda?

[alienb4ndit]

The engine doesn't stop dead as you would expect.. it sort of slowly dies, giving me the impression that there is gas but not enough to keep it running without the help of petrol. That said, its using about 30 litres of LPG to 200 miles (approx).

It's a 2004 2.0Ts

Just been out to look for the ECU, think I've found but its secured to the side of the air box and I can't get it out without tools. I'll have a go tomorrow.

[alienb4ndit]

So what would be my course of action here? Its definitely running on gas and petrol. The trip computer in the car is telling me that the eange on the petrol I have in the tank is being used constantly, the gauge is going down slowly, all whilst its also running on LPG.

Is there anything I can do with a laptop, any relevant software and a lead?

[LPGC]

With some vehicles the petrol gauge (and so range as per fuel computer) go down when running on LPG anyway - There is no direct connection between the level sender in petrol tank and dashboard, the computer that tells the dash fuel gauge where to point only takes an occasional reading from the level sender but calculates where the fuel gauge should point... On such vehicles something like switching off ignition, opening petrol cap, locking doors and then unlocking doors can see the petrol gauge suddenly jump back to correct position.

Mazda are closely related to Ford, which don't have a fuel return to the petrol tank (I don't remember regards your Mazda), the petrol system has a closed loop system of monitoring petrol pressure and adjusting length of pulses to petrol injectors depending on fuel pressure reading. On such vehicles (unless a separate return is fitted), when running on gas (no petrol injectors working), fuel pressure will get higher than normal working range, so petrol pulse duration goes below normal working range. The LPG system works as a slave to the petrol system so correct LPG tuning might depend on unusually high petrol pressure. If even only 1 petrol injector continues to operate, this might be enough to keep petrol fuel pressure reaching the high level.

We don't know what ECU you have yet so cannot advise which software you'd need. Since this is a BRC install it is unlikely anyone besides me on this forum would be able to help even if you had the software and I wouldn't think it likely you having the software would be much help... Could write a book on all the things to look out for, and even then you'd have no experience fixing that type of problem. There are lots of supposedly BRC compatible leads for sale on the net, of which not many work on all the various BRC systems.

Simon

[alienb4ndit]

Ok... whereabouts are you? Maybe I could take a drive over to you (if you're not too far away) and have a look at it.

[LPGC]

I'm in South Elmsall, WF9 2DS, which is between all of Pontefract, Doncaster, Wakefield and Barnsley (10 miles to each).
South Elmsall is where West Yorkshire, South Yorkshire and North Yorkshire meet.

Simon