LPG Discussion Forum

So, my AEB lead has 3 wires, the AC Stag connector on the Saab has 4. Will it work, and what wires( if any) do I need to swop over? I've tried swopping the two data wires (leaving red & black as they are) on the Stag system but it won't connect either way round. No sign of any gas leaks now, but it won't run on gas, presumably because I have to change the injectors in the software. Any suggestions as to how I can get it to connect, still getting error message... ?

Looks like the cyl4 pipe is kinked..

All I can tell you is on mine I have 4 wires on each connector, and the two centre ones are swapped over. I think Simon missed your reply with his reply above, he might be able to suggest whats best to do?

LPGC wrote: Sat Mar 06, 2021 5:59 pm Looks like the cyl4 pipe is kinked..

Only the center two are a bit tight, cyl 1 and 4 are pretty good There's a blanked off stub pipe at the end, which is a gas outlet on the rail, not sure what it's for but I'be always just blanked it off.

Any advice on how to get my lead to work on this system, I'm eager to get connected and try out the new injectors. Currently won't work, I assume because the settings need changing to suit the new injectors...

Brian_H wrote: Sat Mar 06, 2021 6:49 pm All I can tell you is on mine I have 4 wires on each connector, and the two centre ones are swapped over. I think Simon missed your reply with his reply above, he might be able to suggest whats best to do?

I've tried the 2 data wires in both positions, but no luck. I'm wondering if the usb end is different for different systems?

The usb box or lead is the same thing - its just the pinout thats different. Somewhere on the forum (and I can't find it as I can't find the correct search term to use) is a diagram for the wiring for the leads. I don't recall having the stub on my injectors (same type as yours) but as you say blanking off is fine - the end cap can be removed to allow connection to either end of the injectors, or for a balance pipe where required.

The pinout (colours from the AC stag side is as follows
Blue > RXD
Black > GND
Red > +12V RS232
White > TXD

I'd suspect your missing wire should be getting 12v to power the interface. Which is missing from your interface cable for some reason. Hence why its dead? Don't know what lead you've got to advise best way round that issue, there isn't any sign of a missing connection I guess?

Brian_H wrote: Sat Mar 06, 2021 9:41 pm The usb box or lead is the same thing - its just the pinout thats different. Somewhere on the forum (and I can't find it as I can't find the correct search term to use) is a diagram for the wiring for the leads. I don't recall having the stub on my injectors (same type as yours) but as you say blanking off is fine - the end cap can be removed to allow connection to either end of the injectors, or for a balance pipe where required.

For some reason both of the 4 way rails I have do have this stub, whereas the 3 way versions I have on my V6 don't.
As for the lead, I think there's a 12v+ and neg, and two data wires (in & out) on the Stag plug. However, on my lead which still works fine on my AEB systems, there are just 3 wires, a -ve and the two data wires.

I did miss Colin's post just before I posted above.

I believe Bri is right about your cable not working because it's missing one of the power wires. The data wires (the middle 2 on both AEB and Stag) are the only 2 you should think about swapping over. Most cables with 4 pin Superseal plugs for various systems just have the data wires connected one way or the other but have to be careful because there are systems /4 pin Superseal cables that mix up the position of the power wires.

Been a long time since I've tried 3 pin interface cables on AEB or Stag and I don't remember all results from testing various cables on various systems but as an example I can say that a Stag 4 wire USB lead will work on ESGI but an ESGI 3 wire USB lead won't work on Stag.

Early OMVL Superlight injectors were available with the option of gas pressure take-off port (to connect to a remote pressure sensor) or not, those supplied with the port were usually also supplied with a gas temp sensor end fitting (instead of just a stopper for the end of the rail), don't see the type with the port available as often these days.

My 3 wire works fine with my King AEB systems, even though the AEB ECU also has 4 wires in its diagnostic plug. I'm wondering why it won't work with the Stag, given the the only wire missing is the 12v+, and that 12v is fed from the Stag ECU to the laptop lead. Why would the lead need a 12v supply?

Its something to do with conversion from RS232 serial comms to whats coming out of the ecu - theres a voltage change from 5v to 12v in there somewhere. Gillbertd or Simon will probabbly know the specifics as one or the other of them has posted about it before. The basic key point is the interface needs power to work. Sometimes this is provided on the missing pin, other times from the laptop depending on the chipset. Quite why it doesn't work in your case I'm not sure of. You could check whats coming out of each pin on the AEB ones you have to see whats missing though (I'd expect +12v from the diagram?)

Yes Brian, it's the +12v that's missing. I have a new lead today, but still can't connect. I notice the wiring colours are different so maybe need to match the colours up?

What lead have you got now? Wouldn't be trying to swap cables about unless you know it's a lead for the wrong system your trying to use.

Colours often don't match, seems the colours in the wires are whatever the manufacturer had laying around at the time rather than being significant.

Brian_H wrote: Wed Mar 10, 2021 11:01 am What lead have you got now? Wouldn't be trying to swap cables about unless you know it's a lead for the wrong system your trying to use.

It's s lead I just got from lpgshop for the stag system. Should be the correct lead but like I say, it doesn't work and the wire colours don't match up. Have asked the lpgshop but still awaiting a reply...

I'd hang fire until they come back to you, since only 1 wire matches anyway. Better for them to say swap them around than you to do it and cause problems if you need to send it back. That lead should be correct as supplied unlike the aeb ones. Assuming lpgshop have sent you the right lead of course.

Incidentally is it this one?
https://www.lpgshop.co.uk/ac-stag-usb-f ... interface/
If so check your wire colours against the photo....

Brian_H wrote: Wed Mar 10, 2021 1:43 pm Incidentally is it this one?
https://www.lpgshop.co.uk/ac-stag-usb-f ... interface/
If so check your wire colours against the photo....

It is that one, but is not the same as the picture as the one they sent me doesn't have the 'extra' connector in line like shown in their picture. Plug colours the same though...

I'm no expert on these things, but I've got stag system also so can pass on what is working for me.

I had dramas with my initial cable for multiple reasons I think, so I ended up getting CP2102 usb board which is working fine.

12v doesn't need to be connected, I thought. With these boards at least it gets it's power from the usb side at 5v, but sure if the 12v can blow things though.

Connections on mine, that work with stag 300isa2. Numbers are the pin number on the plug that goes into LPG ECU plug.
1 ground
2 transmit
3 receive
4 no connection (12v)

Hopefully that helps you trouble shoot

Hi Stu, I think your system isa2 maybe newer than my Stag 300? Do you have a pic of your diag plug, I'd like to see if it has the same pinouts /colour code as mine?