Hiya my old P38 has an LPG conversion, the wiring for the LPG ecu is rather hapdash and strewn all over the shop I was wondering what it would take to remove it and get the original loom back to factory/petrol spec.

It's a multipoint system would it just be tied in with the petrol injector loom or is it more in depth?

cheers.

It'll have an intercept on each injector feed cutting into the pulse wire on each one, it will also have permanent live, ignition switched live, TPS and it may also have a connection into one of the lambda sensors (may be connected, may not) and an RPM sense from one of the ignition coil feeds although some systems use the injector pulses for RPM.

What system is it?

Cheers it's an AC stag system I believe.

Sorry not got the diagram for the Stag system but it was the preferred option for the cheapo 'done in a day' bodgers so not surprised the wiring has just been chucked in.

Might be on this page: AC Stag Download center

Seems to be the usual cuts into injector wiring, plus a bunch of other stuff ?

The only LPG wiring necessary to connect to original vehicle wiring are the petrol injector break wires and the ignition on wire. There are 16 LPG system petrol injector break wires, each of the 8 original petrol injector wires are cut and an injector break wire connects to each side of the cut. The ignition on wire is usually connected to the positive wire at one of the petrol injectors. There's no connection to TPS, there might be a connection to one or both of the front lambda sensor signal wires but (if so) this will just be a connection (the lambda wire won't be cut). Depending on which AC Stag ECU is fitted (and maybe which installer and how it is set up) there may be a wire connected to a coil pack. Then of course the LPG system needs a power supply so is usually connected directly to the battery. All the other LPG system wires are separate to original vehicle wiring.

Often the injector break wiring is connected close to the petrol injectors, especially on a Thor. On a Gems the injector break wiring might be near petrol injectors or might be near the petrol ECU since on Gems the ECU and it's harness are handy to access near the battery.

Wherever the petrol injector break wiring is connected it is easy to see which original wires were cut. For starters the original petrol injector wires that were cut are a different colour to each petrol injector, so you can match up and reconnect them on that basis. Secondly the 16 LPG system wires that are connected to petrol injector wiring are 8 different coloured pairs of wires, one of each pair is a solid colour, the other of the pair is the same colour with a black stripe, so even if petrol injector wires were all the same colour you could re-match and re-connect petrol injector wires on that basis.

No need to even fully disconnect the (red) ignition on wire, you could just cut that and isolate it, same with any wires connected to lambda sensors.

Why are you removing it @Strangerover?

Ahh cheers.

The LPG system was half missing when I got the car years ago and the wiring is a mess to be honest so in an ideal world i'd like to remove the excess and get her back to factory..

No LPG stations around me anymore so no reason to keep it.

Except to fill up when you are near somewhere and keep your engine in better condition....

I was talking to Mark Skitt, the breaker with a field full of P38s and L322s in Wales, recently. When I told him my current mileage he immediately said I must be running on LPG. He was saying that when pulling a used engine apart if it has been run on petrol, the interior is black, if it has been run on LPG, it is still clean.

Tidy it up by all means but leave it working so you can run on LPG whenever you get the opportunity to fill up (or get a pump from Simon and fill from red bottles).

Agreed with Gilbert.

In recent years I've converted hundreds of Nissan Elgrands, many owners get me to change the spark plugs while I'm at it. Changing the plugs I can get a view through the plug hole into the cylinder, when they come in the piston crowns are always black but after a while of running on LPG they're clean. I avoid running my car on petrol as much as possible, not only for the cost savings of running on LPG but also because if I only run on LPG the oil stays clean between changes.

I have gas delivered to home in 47kg bottles, prices vary but it costs me £79.50 for a 47kg (92 litre) bottle exchange with free delivery. I sell pumps that pump it out of a bottle into the car tank.