Outer Limits 4x4 Board

Hi guys,

Someone has probably already asked this but i can't find it anywhere.

I have an MQ patrol L28 motor on gas, looking to go back to dual fuel but i don't know how to do the wiring for the electrical component, I do know a fair amount about auto electrics so a wiring diagram of some description would sufice but all info is highly appreciated.

Thanks in advance,
Smiley

There are 4 basic components required & they are ......

1/
A 3 position switch ( ON,OFF,ON ). one "on" position runs the petrol side while the other "on" position runs the LPG side. The third pin on the back of the switch (usually the centre pin) is a power wire from the "ignition" switch & must only be live when the engine is running.
Switches designed purely for LPG conversions are marked "petrol & LPG" but an ordinary switch works just as well ( remember to mark it tho )

2/
A "relay" ( there are specific units for this but a std relay works fine)
The relay is wired like ......
a/ earth wire
b/ power wire from the dash switch ( as discused in #1 )
c/ wire from the coil
d/ wire to the LPG lockout valve

basically it works like this ....
switch to LPG position, the power wire from the ignition is passed through the switch and then to the relay, the relay then uses that "power signal" to activate, it takes its secondary signal from the coil and provided the coil is in the "runing" phase, the relay will then allow a power signal to the LPG lockout valve.
All the relay does is act as a safety switch so that the LPG lockout valve cant be opened unless the engine is in the "run" position at the key and there is power at the coil.

3/
LPG lockout valve lives at the end of the line from the LPG tank and just before the "Converter". It is designed to stop the flow of LPG when the vehicle is not running or running but not on LPG.
There will be an additional LPG lockout valve on the LPG tank and this valve should be wired inconjunction with the valve at the converter....
IE: both valves are "opened" at the same time and by the same switching via the relay.

4/
Petrol lockout valve should be mounted betwen the fuel pump and carby but be as close as posiable to the carby as practiable. The petrol lockout valve is "opened" only when the dash switch is in the "petrol" position. There is no need for the petrol lockout valve to be wired through a relay like the LPG side is.
NB: for ADR compliance most petrol engines run a "fuel return line". You will see "2" fuel lines ( one may be larger then the other ) and then the 2 lines are joined at a given point and then a single fuel line runs to the carby form this junction block. On the L28 the junction block is directly above cylinder number 2 and on the passengers side of the rocker cover. Fit the petrol lockout valve AFTER the junction block.

TIP:
all the wiring can be easilly done using a std 5core trailer flex loom and its cheap as too

Kingy

Just remember with 3 way switches when you click
one side down it makes contact with the centre pin and the pin on the opposite side of the switch I will try and find a pic to show you or perhaps someone can explain better

Tom

Thanks guys

that is really helpful

one other thing i forgot to mention, the petrol has an electric pump, how will haing a shutoff affect it (eg: pumping under pressure, will it just pump back through the return) will i have to wire it up as well to stop it pumping while running on gas.

Thanks
smiley

smiley wrote:Thanks guys

that is really helpful

one other thing i forgot to mention, the petrol has an electric pump, how will haing a shutoff affect it (eg: pumping under pressure, will it just pump back through the return) will i have to wire it up as well to stop it pumping while running on gas.

Thanks
smiley

Two schools of thought on this, most leave it connected and that keeps fuel in the rail and it just come back along the return line.

The only disadvantage to running this setup is that if you use up all the fuel the pump will run dry and destroy itself.

When I enquired about this when I was doing my LPG I was told that the standard now was to leave the pump running and that is how all the installers complete the jobs.

For me I chose the other way, the risk is that more fuel system components will dry out and fail quicker - my tank is rather small so I end up running a day on fuel a week at least so i don't see it as a problem, the other thing that made it easy for me was the power feed for the fuel pump was in the same plug I was modifiying for the injectors so it was hardly any extra work

I think Kingy will confirm that you should leave the pump running

Do whatever suits you IMO understand the differences and risks

Tom

As Tom said........

Best to leave it connected as that is the "normal" way.....

But.....
here's a few things in both the plus and minus side of things to consider

The plus side is that the fuel is constantly being "rotated" between the tank and fuel line and the system operates as per normal, this way fuel is less likely to go "off" or become contaminated from being stagnet within the fuel line.

A minus side is that the fuel pump is working when it doesnt have to and the pressure its pumping is slightly increased. The reason for the increase is that the "block" which joins the two lines together has a restrictive baffle which only allows a small amount of fuel to return to the fuel tank whilst the remainder is pressured into the carby. Its this baffle that increases the work load on the fuel pumps.

A plus side is ...... less wires to run
Although its far from difficult to include the fuel pumps into the loom for the LPG/Petrol switch most ppl are just plain lazy ( including the LPG conversion places ). It takes around 10 minutes to include the fuel pumps into the LPG/Petrol switch..... big deal hey !



Really its entirely up to you as to whether you do or dont include the fuel pumps in the wireing.....
My rig runs a 38 lit fuel tank and twin LPG tanks & my fuel pumps are only running when the switch is in the petrol position...... However my other V8 rig runs both an electrical pump and a mechanicle pump and both are running even when the LPG is "on".....you cant switch off a mechanicle fuel pump !


Heads or tails ?

Your call

Kingy

Thanks guys

That helps heaps

Smiley my MQ runs duel fuel and is fitted with an electric fuel pump which turns off when selected to gas.

The 3 position switch is :

Top.... GAS

Middle.....Switches Petrol off but allows to run on fuel till fuel bowl is empty

Bottom....PETROL

The reasoning for the middle position is that petrol and gas does not like to be mixed together and will run like a busted arse till all petrol is used up, the middle position allows the contents of the fuel bowl to be consumed first before switching to the gas setting.

You have to remember even though your only using the carby as a transission piece to get the gas into the cylinders any petrol remaining in the carby will still be made tofollow its normal course of events.