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PostPosted: Wed Sep 12, 2018 3:48 pm 
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Hi,
I've almost completed a swap in my vehicle from aircooled to a more modern watercooled engine and now I am almost there with reconnecting my LPG system. Im quite excited but even though so near it seems miles away. I have hit 3 problems in reconnecting my LPG system in the wiring side of things.

The old engine was 1975 and aircooled so basic. My 'modern' engine is a 1995 with a coil pack. I have a brown wire to connect to the coil, for rpm feed, but I look at my modern coil pack and I can't figure how it connects to this in any way, its like a closed system with 4 plug leads. I guess I break into the ECU but its 5v, is that enough?

Secondly I've purchased (recommended by the LPG shop) an inline water temp sensor to replace my old in-exhaust sensor. Would I be right to simply wire this up to my 'old' exhaust feed wires.

Lastly my injectors, I have traced 4 wires in the loom that directly run to the exisitng petrol injectors. Its a loop that I break into but I wonder does it matter to the LPG ECU which way round the wires are? so for example I have green/green w stripe, brown and brown with stripe etc i.e will it just break the feeds or allow continuous supply.

thanks again for the help,

Kevin


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PostPosted: Wed Sep 12, 2018 5:00 pm 
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You haven't said which LPG system your fitting, but the leads for the injectors should be installed a specific way around, typically the solid one want to goto the cable supplying the negative side of the injector, the one with the stripe wants to go to the loom. Typically you won't get the injector pulse shown in the lpg software for the petrol injector in question if its wrong. Equally it needs to be on the right side of the injector (the negative side) as this is what does the triggering of the injector.

On the exhaust sensor - probably ok, but for anyone to confirm it would help if you gave details of the old and new sensors, and the ecu your fitting?

On the coil pack typically you will have at least 2 trigger wires if you are working on a 4 cylinder engine (2 if its wasted spark, maybe 4 if not). Shouldn't matter which you connect to provided its a trigger wire (you do a t connection to that wire, somewhere on its way into the coil pack from the engine loom). If you give info on what engine it is theres a reasonable chance someone here can tell you which colour wires will work, otherwise you can test with a multimeter, you want one of the wires at 0v when the ignition is on - on the side of the coil pack connector where it feeds back into the engine loom, not the HT side).


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PostPosted: Wed Sep 12, 2018 6:00 pm 
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thank you, its a stag 300 system.

I will double check the injector connectors tomorrow. If its negative does it (the wire I need to locate) have continuity to the body (negative = earth ?)

and when you say 'trigger wire' is 5v sufficient ? Its a Subaru Legacy 2.0l engine, normally aspirated, 1994, if someone knows the wires that would be brilliant.

many thanks


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PostPosted: Wed Sep 12, 2018 6:33 pm 
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No, it will go to the ecu so wont have connection directly to earth. It's the wire that doesn't have 12v on with ignition switched on and injectors unplugged. 5v shouldn't be a problem but again you need the negative trigger wires. Hopefully someone can tell you what wires to pick there.


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PostPosted: Wed Sep 12, 2018 6:40 pm 
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That's great, thank you


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PostPosted: Wed Sep 12, 2018 8:43 pm 
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Big difference between a water cooled flat 4 VW engine and a flat 4 Subaru engine - Bare in mind the system will need complete re-calibration after you've got the wiring sorted.

Wiring on Stag (cylinder / channel numbers) is 1 yellow, 2 green, 3 red, 4 blue (the exact opposite of AEB colours). Bri is right in you need to connect the striped coloured wire to the petrol ECU side of negative wire to petrol injector cut (unstriped to same injector side of cut). It doesn't matter which colour group wires go to which petrol injector as long as the colour wires to the LPG injector on that cylinder matches.

Even if you connect the rpm wire to the correct coilpack wire you'll still find it won't try to switch over until rpm's are 2x the rpm it changed over at on the VW engine - until settings have been changed in the ECU. Since you're unsure which is the correct wire on the coilpack and since you'll have to re-calibrate anyway you might as well wait until connected to a laptop to find the correct wire. 1995 Subaru engine with coil pack on top which has 4 wires, at least 2 of those wires will be correct to connect to.

If the VW engine didn't have a lambda probe then calibration on the Subaru engine should be much simpler (because the closed loop fuelling provides an easy method of interpreting feedback as to whether LPG calibration is rich/lean).

But all this may be wrong from the outset - You said the VW engine was a 1975 aircooled... which I'd expect to have a carb. Stag 300 won't work with a carb so this poses the question.. Had you already added EFI from a later model engine to the 1975 engine? If you didn't have the Stag 300 system on the 1975 engine (and if the old engine had a carb) you'll need to change the reducer from a mixer system reducer to a gas injection type reducer and plumb it into the engine heater circuit (a mixer system reducer on an aircooled engine would only have a liquid gas preheat system which effectively just routes the liquid gas feed around the hot exhaust, probably insufficient heating for an injection system reducer).

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Last edited by LPGC on Wed Sep 12, 2018 10:01 pm, edited 1 time in total.

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PostPosted: Wed Sep 12, 2018 9:15 pm 
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That's a great reply and one I'll print it tomorrow to study.

The original vw air-cooled engine you are correct did not have a lamda but I have a wire that needs to be connected. The VW engine was an early fuel injection with ECU etc so I'm not far from being completed.

I have the lead to connect the system to PC and the software but it's been ages since I've used it (another learning curve to come :).

I didn't understand this bit "you might as well wait until connected to a laptop to find the correct wire."
How would the software identify the wire in way?

So in a nutshell I had 1975 fuel injected air cooled engine which I've replaced with 1994 Subaru water cooled, also fuel injected. (Took huge amount of effort!)

Really appreciate your input,
Kevin.


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PostPosted: Wed Sep 12, 2018 9:19 pm 
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As long as you don't try tapping into the HT side (the output from the coil pack onto the plugs) you will either get a rpm reading (which could be double or half what you'd expect depending on the config on the gas ecu and the way the coils are fired) or you won't get anything, in which case you have the wrong wire. If you get an RPM reading then your on the right wire, but may need to work out which setting your using in the software to get the correct reading.


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PostPosted: Wed Sep 12, 2018 9:25 pm 
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If you don't connect to the correct wire the software will show zero rpm or maybe flick between zero and some occasional silly figure. If you connect to a correct wire the software will show half actual rpm until you've changed (in software) 'number of cylinders for coil' to 'double coil' or wording to the same effect, then should show correct rpm. You can't hurt anything by trying any of the coil pack wires (except obviously the high tension plug wires lol).

Post crossed with Bri's but I might as well leave this standing.

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PostPosted: Wed Sep 12, 2018 9:29 pm 
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Thank you very much. I will carefully work through this tomorrow.


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PostPosted: Wed Sep 12, 2018 9:35 pm 
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Might as well save your current software settings then reset the ECU before starting calibration from scratch. The map slope for the old VW engine will be much steeper than what it will need to be for the Subaru engine.

So just to clarify, the 1974 VW engine had EFi pulsed port fuel injection (not K Jetronic) and you had the Stag 300 system working on that engine? I'd be interested in the spec of the temp sensor (reducer or exhaust?)... If it's just a normal reducer temp sensor attached to the reducer you didn't need to buy the inline water temp sensor.

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PostPosted: Thu Sep 13, 2018 9:03 am 
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LPGC wrote:
So just to clarify, the 1974 VW engine had EFi pulsed port fuel injection (not K Jetronic) and you had the Stag 300 system working on that engine? I'd be interested in the spec of the temp sensor (reducer or exhaust?)... If it's just a normal reducer temp sensor attached to the reducer you didn't need to buy the inline water temp sensor.

Hi, It was a early L Jet Bosch Fi system on my 1975 VW camper and was working great until the old engine/crank went bang. Not economical to repair for what I wanted from the vehicle. Whilst rebuilding the new engine I drilled out all the nozzles and got everything in place which is why I am quite close but not quite over the line.

The temp sensor went into the exhaust. I have cut this and the 2 wires will now connect to the inline water temp sensor which is this one. Lovato


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PostPosted: Thu Sep 13, 2018 5:02 pm 
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That's all in order so far then Kevin

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PostPosted: Thu Sep 13, 2018 7:46 pm 
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a quick update, I have successfully located all the wires, took a bit longer as I wanted to be sure they were correct. Light fades so quickly now so tomorrow I cut and solder.

Bar setting it up (borrowing a friends laptop) the only wire I seem to have 'loose' is for the lambda sensor and this one has also got me stumped.

my old aircooled VW never had a lambda sensor, engine was way too old. My replacement 1995 engine does have one albeit probably quite limited in what it does compared to modern cars.

I have an aftermarket lamda sensor with 3 wires, red, white and black. On my stag 300 loom I have 'violet' and a 'violet-grey'. In leads description it says violet grey is for lambda 2, in the diagram violet-grey is part of the circuit regardless of one or 2 sensors ... so thats a contradiction.

Second (main Q) is what is the right wire to connect it to.

Thanks again for the input and assistance, its been really helpful and productive

Kevin


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PostPosted: Thu Sep 13, 2018 8:37 pm 
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You don't have to even connect to lambda but if you do just connect the violet to the black wire from the probe that's already fitted. Connecting to lambda doesn't effect anything other than showing the lambda voltage on screen but this helps set correct mixture at high engine loads when the petrol system is running in open loop mode.

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PostPosted: Sat Sep 15, 2018 8:56 am 
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Great progress, it's all connected. I need a laptop now as it's beeping at me (is there an error code crib sheet?) .
As it's beeping when I turn on the ignition I haven't tried starting it up yet , I'm quite wary of it.
Thank you again :)


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PostPosted: Sat Sep 15, 2018 4:13 pm 
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Well I connected laptop with software but it's stubbornly telling me I have no lpg controller.
The vehicle starts and runs ok so that's good but I don't know why it cannot see the controller?
Any ideas or guidance appreciated :-)

I tried ign off then on before running software, checking the usb connection, disconnected the controller and then connected but to no avail :-/


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PostPosted: Sat Sep 15, 2018 5:32 pm 
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First thing is have a look from device manager in windows that the com port the cable creates is something sensible - if you have no serial ports on the laptop then com1 should be ideal, otherwise go for com2/3/4. If it can see that then that should suggest the drivers are installed correctly for it.

There should be two live supplies to the lpg controller - one from the battery, the other is usually taken from petrol injector positive (but can be any ignition switched positive). It may be one of those it isn't seeing, worth a check of the fuse holder on the battery connection as some of them suffer with corrosion over time. Might also be an idea to check you have voltage going through both of them with a multimeter.

Otherwise its possible that you have a duff lead, but given its beeping it suggests its finding a problem so doubt its the lead, more likely some sort of wiring issue

It might help to get hold of the wiring diagram if you don't already have it, plus the instrctions from this link (sorry don't know which stag 300 you have, hopefully either you do or Simon can tell you) > https://www.ac.com.pl/download-center-Instructions

If you scroll down the manual theres this bit about the beeping
4.3.
Acoustic signals
The controller generates the following acoustic signals:

Three acoustic signals – when switching from LPG to petrol because of low LPG level in the tank

Three short acoustic signals followed by a long one – when a controller error occurs

When switching the ignition on - two short signals followed by a long one indicate a scheduled service visit. Visit a service station to have your system checked

Three long signals repeated every minute – the car started in the emergency mode.

Probably not much help, as I'd read it you need to setup the controller to clear the error before you can go further.

Might be a daft question, but is this the same controller you were using with the aircooled engine?


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PostPosted: Sat Sep 15, 2018 6:22 pm 
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Agree with what Bri said on connection issues.
What version of Stag software are you using? Software for Qbox (which has low version numbers because Qbox is relatively new) won't work with none Qbox ECU's (and vice/versa) but the 'normal' Stag software started at early version numbers and has since passed V11... Early Stag4's for sure and early 300s need low version number 'normal' Stag software but don't confuse low version number 'normal' with low version number Qbox.

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PostPosted: Sat Sep 15, 2018 10:20 pm 
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Hi, it's a stag 300-4, same everything as I had with the air-cooled engine and I used the same cd that came with the lead and controller as first supplied. It prompted me to upgrade. I've stuck to stag 300. The laptop is an old one running xp.
From the accoustic codes that I get when ign on it tallies to controller error.

Tomorrow I'll double check the live feeds mentioned. I can't borrow the laptop again until Monday evening so it will be good time to go over my connections carefully.

I'm thinking I should be able to disconnect the big controller plug and check the back of that for voltage as the feed goes into the controller, not out.

Many thanks
Kevin


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