Exhaust manifold colour

[pibby]

Here’s the exhaust manifold for cylinders 2/4/6/8. the vehicle is running lpg. So I was wondering why 2 & 8 are so sooty (they are dry even though it looks wet and the car doesn’t burn oil) and 4 & 6 are so clean. I did a compression test and they are all between 185-190 psi. the spark plugs are not fouled at all. I’ve got a feeling the lpg gas injector bank is playing up based on the oxy sensor readings while driving but I wouldn’t have thought it would cause this as lpg is clean.

Any ideas.

Thanks.



http://www.aulro.com/afvb/attachment.php?attachmentid=27769&stc=1&d=1281853141

[Tombie]

Does your LPG system start the vehicle on Petrol then swing over to LPG later?

[PhilipA]

My first ideas are
1 The injectors on 2 and 8 are leaking
2 The Gas injector loom is wired incorrectly and 2 and 8 should be on the other bank. Does it have 2 x02 sensors?
Regards Philip A

[pibby]

the car does start on petrol then switches to lpg. in a previous troubleshooting exercise i had checked that the lpg wiring was aligned to the correct cylinders. there are two oxy sensors.

leaking injectors - sounds a likely candidate. the fuel system loses its pressure overnight and takes more revolutions than it should normally need to start on petrol cold. I have a thor fuel rail (see below) which I will be installing – is it possible to test the injectors to see if they are leaking before I go to the trouble of installing it on the car. I would prefer not to recondition them or get new ones as aside from starting on petrol I drive on lpg.

i have got myself a thor manifold which i am going to install once i get my head around it. philip - i have read your posts on your install and advice you have given to others on such. so far my main concern is the fuel pump. i looked at rave and it says the disco fuel pressure regulator tries to maintain 2.5 bar above inlet manifold pressure and has a return line. the fuel pump used with the thor aims for 3.5 bar and has no return line. Was this an issue for you and if so how did you work around it? I am sure there will be plenty of other things to resolve such as cables (kickdown/throttle/cruise), connecting AFM etc but I don’t see these as show stoppers more time consuming and fiddly to work around. There may be some machining work as you say as well.

thanks.

Brett.

[PhilipA]

I wanted the most simple and reliable set up that I could get parts for by referring to 14CUX numbers.
So I fitted the 14CUX rail and injectors( though I bought replacement 4 hole injectors from the USA) to the Thor manifold.
The rail will fit to the original regulator IF the rail is a RRC rail with the regulator on the RH side of the rail. You have to grind/cut the coil brackets off and it is a tight fit. BUT the big advantage is that you have a completely stock fuel system with OEM pressure joints.
The rail fitting tabs are in a slightly different place but I just put a couple of washers under the bolts and it fits fine. I think I may have cut the tabs a bit.
By using the 14CUX rail you can get a fuel pump anywhere as it is a Commodore pump whereas the Thor pump would be a real problem in the bush. I do not know how you would fit a Thor sytem as you need a pump/gauge /regulator system from a D2 and I have no idea whether they fit into a Disco 1 tank.
In the words of Sir Humphrey , it would be a courageous decision to go to Thor injectors and rail.
Regards Philip A

[pibby]

ok. makes sense. i assumed the thor manifold needed the thor fuel rail - but not so. should be possible then keep 14cux fuel rail - the engine is a 4.6 block but 3.9 bolt on bits. thanks philip.

this maybe what has been upsetting the lambda readings on that bank - i was putting it down to the lpg injector bank playing up. is there a way to tell if the injectors are leaking on the other side without pulling the exhaust manifold off? the spark plugs on ths side didn't give the game away.

[mike 90 RR]

is there a way to tell if the injectors are leaking on the other side without pulling the exhaust manifold off?

Yes there is a way

Unbolt & remove the Plentium .. .(your gonna do that anyway)
Your fuel rail should be now visible with no obstructions

Unbolt the fuel rail ......
Your injectors are held to the fuel rail with metal spade retaining clips ... Make sure each injector has this clip ...If there is no retaining clip then abandon this method .... as the fuel pump will blow the injectors off the rail, with fuel being sprayed everywhere

Now go down to the Local store ... and buy some disposable clear plastic drink cups

Now lift up the unbolted fuel rail, complete with the injectors attached, and put a plastic cup under each injector .... rest all 8 injectors inside the 8 plastic cups

Turn on the ignition ... Fuel pump pumps up ... If you have a leaky injector ... you can now see it


Another bonus to this is ... Disconnect the coil H/T lead ... turn the motor over, and you can see the spray pattern .... AND ... you can measure the flow rate / amount to see if the injectors are balanced


Cheers
Mike