PLEASE HELP

[adam1978]

Hi all
Is there anyone in the grantham area who can offer me some cheap guidance ??
I have a 2002 preivia and im struggling with the wiring to the petrol injectors, everything else is done.

[Gilbertd]

Not Stag specific so your colours may well be different but this is how it should be wired.

[adam1978]

i have two wires to injector number 1 from the main loom I understand i need to find the positive/negative etc.
But I have one yellow one black for injector 1 also i have 1 yellow and one black all from lpg loom.
just dont know how to get these for wires into two?? the picture doesent really help.
I did it how i thought was right but have flooded the engine

[Gilbertd]

i have two wires to injector number 1 from the main loom I understand i need to find the positive/negative etc.

Yes, you need to identify which one has an ignition switched 12v supply on it and leave it alone, it is the other one, the negative that you need to splice into.

But I have one yellow one black for injector 1 also i have 1 yellow and one black all from lpg loom.
just dont know how to get these for wires into two?? the picture doesent really help.

Well the picture is about as clear as it can be. You have two wires from the petrol ECU to each injector, one of these will be the positive. As I know nothing much about the Previa, lets assume they use the same arse about face logic as Ford and say the black is the ignition switched positive (and not negative as standard DC wiring would assume). In that case, leave the black alone (this is the one shown on the diagram as the wire with a + next to it that just sort of hangs in mid air) and cut the other wire, the yellow in your case (I assume the other injectors are black plus another colour, in which case it does use the arse about face Ford logical colour code). You also have two wires coming from your LPG loom that need to go to injector 1. Connect the yellow one from the LPG loom to the cut end of the original yellow wire that goes to the petrol injector and the black one from the LPG loom to the cut end of the original yellow wire that goes to the petrol ECU. You are intercepting the pulses from the petrol ECU to the petrol injectors. When the engine is switched to run on petrol, it simply connects these wires together so the pulses goes from ECU round a big loop to the LPG ECU and back to the petrol injector. When running on gas, it breaks the loop so that the pulses are used to trigger the LPG ECU to tell it to fire the gas injectors and never get anywhere near the petrol injectors so they stay shut.

I did it how i thought was right but have flooded the engine :(

I can't quite work out how you could have cut 2 wires, added two more (which would give you a total of 6 ends) and joined them back together in such a way as to have ignition switched positive and a permanent negative at the petrol injectors, but it seems you did. As soon as you turned the ignition on, the petrol injectors opened and you managed to fill the combustion chambers.

[adam1978]

How can I tell which is the positive???

[Gilbertd]

Get the two wires that did go to the petrol injector before you started cutting, remove the petrol pump fuse or relay, connect the negative lead of your voltmeter to ground, switch on ignition, touch the positive lead of your voltmeter to one of the two wires coming from the petrol ECU that would have gone to the petrol injector, if your meter does nothing, touch it on the other one, the one that causes the meter to read 12 v is the positive.

[Tubbs]

Ok you sound like you have yourself in a muddle. Just because the existing wiring loom happens to have the same colours as the gas wiring loom doesn't mean they bear any correlation to each other what so ever.
So what i want to know is as you look at the injector plugs from the existing petrol injectors what colours have you got on each injector. Write them down and report back. You also need to have a look at your wiring diagram that you have with the kit. It will show you which wiring colours from the LPG loom will correspond with which injector (cylinder) on the engine.

[billynoband]

I think what confuses a lot of people with 12v vehicles is that the wiring is mostly negative switched with the live linked together a lot of the time. We are all used to live being switched from our house wiring .

[adam1978]

I have grasped the coloured wires, but im left with black wires!! where do these go??
I dont grasp the stag 4 diagram.

[Dualtech]

I think the black wires you are refering to are on the gas loom? If this is correct then you can ignore them, if you delve a little deeper into the wires you will see that all they origanaly did was to loop from one plug to the other/before you cut the plugs of the loom/ this was simply to connect the positive of the petrol injector from one plug to another. Give them a tug and see if them come out. If they do infact go all the way back to the gas ecu then it could be that the system allows you to select the +/- polarity of the plugs, altough I doubt it, But if this is the case then just join the ends together.

[Gilbertd]

This has got so confusing now I'm getting totally lost. How many wires per cylinder do you have in the gas loom? I suspect 2, one coloured and one black. How many wires do you have in the original loom going to each injector? Again, I suspect 2, one coloured and one black.

Any chance of scanning the Stag diagram and attaching it? Any chance of scanning the wiring diagram for the car from your Haynes manual and attaching that?

[adam1978]

I think the black wires you are refering to are on the gas loom? If this is correct then you can ignore them, if you delve a little deeper into the wires you will see that all they origanaly did was to loop from one plug to the other/before you cut the plugs of the loom/ this was simply to connect the positive of the petrol injector from one plug to another. Give them a tug and see if them come out. If they do infact go all the way back to the gas ecu then it could be that the system allows you to select the +/- polarity of the plugs, altough I doubt it, But if this is the case then just join the ends together.

I pulled the black wires and yes they came straight out so that helps!! less wires
I have found the wire with 12v so have put back to the injector as it was, the solid colour (yellow) to negative injector then the mixed colour (yellow/black) to the ecu wire.
same for all the other injectors, is this right???
I have put it all back together and tried to start on petrol but no luck, it did cough and splutter as if it was going to then the battery gave up.
Yes I connected the pump relay!!
The smell of petrol is back so ive taken the plugs out but they look drier than the first time, so hoping its just the battery not having enough clout.

[Gilbertd]

If you have just spliced the wires in but not connected the LPG ECU, then there is nothing to join the wires together for running on petrol. The cough and splutter may have been it firing on what fuel was left sloshing around after your previous flood.

Below is a diagram showing how it fits into the existing petrol injector wiring. As you can see, if you have spliced into the wiring but not connected the gas ECU it isn't going to run on petrol.

[adam1978]

Lpg ecu connected and talking to laptop, gauge inside car is working too, should it start?

[Gilbertd]

On petrol, yes. On gas, who knows. It is going to need calibrating but it may be close enough to run sort of as it is.

[Tubbs]

I think the black wires you are refering to are on the gas loom? If this is correct then you can ignore them, if you delve a little deeper into the wires you will see that all they origanaly did was to loop from one plug to the other/before you cut the plugs of the loom/ this was simply to connect the positive of the petrol injector from one plug to another. Give them a tug and see if them come out. If they do infact go all the way back to the gas ecu then it could be that the system allows you to select the +/- polarity of the plugs, altough I doubt it, But if this is the case then just join the ends together.

I pulled the black wires and yes they came straight out so that helps!! less wires
I have found the wire with 12v so have put back to the injector as it was, the solid colour (yellow) to negative injector then the mixed colour (yellow/black) to the ecu wire.
same for all the other injectors, is this right???
I have put it all back together and tried to start on petrol but no luck, it did cough and splutter as if it was going to then the battery gave up.
Yes I connected the pump relay!!
The smell of petrol is back so ive taken the plugs out but they look drier than the first time, so hoping its just the battery not having enough clout.

I dont know if its the same but the colours actually correspond with each cylinder on an italian system. Just worth bearing in mind.

[adam1978]

Do I need to set up lpg ecu for it to run on petrol??

[Tubbs]

No it just needs to be plugged in, it wont even need a fuse or any wiring to be connected as long as its plugged in. They are all designed to default to run on petrol incase a fuse blows or whatever.

[Dualtech]

Sound like you have it right, tbh even if your on the pos instead of neg it would still run on petrol. Probably just your battery.
Cheers, Mick

[adam1978]

I now have no spark the car did have an ac sgi system before just wondering if partially removing that system has upset the feed to coils