LPG / Immobiliser issue

[Stuzewheels]

Cars been going great on gas since Gilbertd did tuning. Came back from 1200 mile trip to france last week. Only problem I have experienced is that to start on gas even when the car is hot, at a filling station say, the car might drive ten foot and cut out. Not sure if this is due to double fueling so I try to remember always to start on petrol.

At the tip the other day I tried to start the car and remembered that the car was on gas, so possibly switched to petrol simultaneously as turning the starter switch. Lights on LPG switch went out. Car immobiliser seems to no longer work but car starts OK on petrol.

May be no link to these circumstances. Merc fitted immobilisers are notorously fickle as they get older. Checked 7.5 fuse which I think runs from starter switch and it was ok. Need to check power going through the fuse. Not in easy position to check.

I beleive there should also be a 7.5amp power fuse on the Leonardo system from the battery which I need check. Would this be in the boot near to the battery presumeably?

Not sure if I spiked the gas ECU system by switching. Immobiliser systems don't publish
their circuitry but they do link to the ign. switch.
Any thoughts come to mind as to where to check first? Many thanks

[Gilbertd]

Stu, it always will start on petrol, even if the switch is in the gas position. If the switch is in the petrol position it will start and run on petrol until switched over, if in the gas position it will start on petrol and switch over as soon as it reaches whatever revs we set it at to changeover. You can make it start on gas and never use any petrol but that involves turning on the ignition, flicking the switch from gas to petrol and back to gas again and starting the car without turning off the ignition. You may have got it confused by doing half of this process but I wouldn't expect it to do any harm.

Dying after a few feet suggests that it is switching but there isn't enough overlap between turning the gas on and the petrol off and the gas hasn't got there (you've got a pretty huge plenum chamber and intake manifold for the gas to work it's way through on that car). Although where the gas is going is a different matter. Has it always done it or has it only started recently? Does it only do it when hot? Do you normally leave the switch in the gas position or do you switch to petrol and manually change over (if you do, why?)?

There will be two fuses, both 7.5A, one in the permanent live and one in the ignition switched live supplies. No idea where they will be located on your car though.

[Stuzewheels]

I tend to start it from cold set on petrol and switch to gas after say five minutes - and no problem. Sometimes I've forgotten to switch it back to petrol and its started OK.

On a few occasions its cut out when the engine is hot and i've started away from somewhere on gas. Not every time.

Because the usual immobiliser indicator flashing sequence didn't occur when i got back into the car after dumping my rubbish, I thought about the car cutting out and hence switched to petrol whilst starting. All lights on the switch were lit (the tank being low) and then all went out. The car started and has done since every time on petrol.

The immobiliser is definately not now doing its job. The usual indicator flashing sequence and door handle flashing light to show the car is alarmed when locked, is not happening. I can live with this.

I'll check to see if switching back and forth corrects the situation with the lpg. Maybe unplug the switch and plug in again. check the cable from ignition switch for continuity through the fuse. The cable is so short its difficult to see but it could be corroded and no longer be connecting. Lifting the fuse box to get to it may be necessary or I'll have to run a new cable from the ignition switch with some slack - neither option appeals much!

I didn't realise it should be left on lpg setting so I'll do this once I've solved the problem.

[Stuzewheels]

Just thought - I can splice into the cable from the Starter switch the ECU side of the fuse to see if current flowing - Doh!

[Gilbertd]

I didn't realise it should be left on lpg setting so I'll do this once I've solved the problem.

I always leave mine in the gas position, on a really cold day it might run a bit lumpy for the first 10 seconds or so but I can live with that (when it's been left overnight it takes at least that long for the ABS to come up to pressure so I'd rather not drive off only to find I've got no brakes!). The only time I touch the switch is to change over to petrol when it starts to slow down because it's running out of gas.

Check the fuseholders, they can go high resistance over time. One thought, maybe the failed immobiliser is relevant. As we don't know where the power feeds have been taken from for the LPG system, it's always possible that the permanent live has been taken from the alarm/immobiliser unit so the permanent live is permanent only when the car is unlocked. It would make sense thinking about it. If the immobiliser is active but the LPG system is live, it would make it easier to start the car if you wanted to steal it.

Might be worth disconnecting the battery for a few minutes to see if it's possible to kick the immobiliser system back into life.

[Stuzewheels]

Thanks Richard makes sense. I have already tried disconnecting then battery and re-synching the immobiliser. Will do some more checking.

[Stuzewheels]

I've left this problem as been doing no real mileage recently. Trip to Stansted Airport shortly on petrol as not yet cut the two immobiliser wires and joined to see if this not only cuts out the now defunct immobiliser but restores the lpg feed.
Traced back immobiliser wires to behind passenger airbag but not seen exactly where they were cut in and don't trust others advice on joining two wires without seeing that they were originally one wire. Well, not before my holiday as pre-paid Stansted extortionate parking costs!
Did find 12v power to LPG ECU has current flowing. Still suspect is that fuse to ignition switch which means raising the fuse box and seeing where it runs to. The W140 series having dodgy wiring looms during the early 90's (disintegrating) I've postponed that inspection. Do have a spare s/h loom if disaster strikes
On my return from a hopefully hot holiday in Frejus will sort this problem -no doubt with a little help from you guys on this forum!

[sijones]

(when it's been left overnight it takes at least that long for the ABS to come up to pressure so I'd rather not drive off only to find I've got no brakes!).

You'll always have brakes!, even if the ABS wasn't powered, and you shouldn't need to wait for anything to do with ABS, the vacuum off the engine gives you the brake assist not ABS...!!!

[Taught2BeCautious]

On the W140, the door locking control unit is in a padded compartment under the offside rear passenger seat, and can fill with water if you have a leaky boot-lid seal.

The central locking and immobiliser circuits are also first to suffer if the battery is not 100% and when my 1996 W140 started playing up (engine cutting out, alarm going off at random times, etc.), a new battery sorted it even though it was still starting without problems.

GSF and Euro Parts will do a free computerised battery check - might be worth doing.

Alan.

[Gilbertd]

You'll always have brakes!, even if the ABS wasn't powered, and you shouldn't need to wait for anything to do with ABS, the vacuum off the engine gives you the brake assist not ABS...!!!

Not on a P38 Range Rover. It's a fully powered system with a pressure accumulator to store enough for 30 applications after the pump stops, there's no conventional servo to use engine vacuum. It takes about 20 seconds to come up to pressure if it's been left overnight and if you try the brake pedal either before you switch it on or immediately you've started it, it's like trying to compress a brick. It'll do something but not a lot!

[Stuzewheels]

On the W140, the door locking control unit is in a padded compartment under the offside rear passenger seat, and can fill with water if you have a leaky boot-lid seal.

The central locking and immobiliser circuits are also first to suffer if the battery is not 100% and when my 1996 W140 started playing up (engine cutting out, alarm going off at random times, etc.), a new battery sorted it even though it was still starting without problems.

GSF and Euro Parts will do a free computerised battery check - might be worth doing.

Alan.

Thanks for advice. I've checked under the rear seat and its dry. The battery is not so old and I started the car first time after a ten days stand at Stansted Airport recnetly. Been having another look at the two 7.5amp fuses under bonnet.
Managed to raise the fuse banks for the difficult to reach one and then realised the cable red/black was held in by a rectangular rubber grommet in the front of the fuse box. Raised this and able to pull out a bit more cable. Having changed the fuse holder etc, no power is being carried along this cable even when ignition on. Assuming its the main power line on Leonardo 175. Now their is a red cable that runs to a 7.5 fuse holder nearby and runs into the Injector Emulator. Not sure if this is the ignition feed as it runs from a splice into a blue cable. I have the car system wiring diagram and there should be a red/black cable fused 7.5 to stoplamp switch so I may be confusing it. (not sure how this earths).
Don't know if this link will open but maybe someone can tell where the power / ignition cables to Leonardo run from? Big ask I know.
http://www.autolib.diakom.ru/CAR/Merced ... S/5915.pdf

[demonicwillow]

You'll always have brakes!, even if the ABS wasn't powered, and you shouldn't need to wait for anything to do with ABS, the vacuum off the engine gives you the brake assist not ABS...!!!

Not on a P38 Range Rover. It's a fully powered system with a pressure accumulator to store enough for 30 applications after the pump stops, there's no conventional servo to use engine vacuum. It takes about 20 seconds to come up to pressure if it's been left overnight and if you try the brake pedal either before you switch it on or immediately you've started it, it's like trying to compress a brick. It'll do something but not a lot!

So your P38 brakes require air pressure stored in a tank similar to a bus or a truck for assisted braking ... is that standeard oem or a modification ??

[Stuzewheels]

Returning to the thread issue, I suppose if I can't seem to find the trail of the two power supplies to the Leonardo ECU I can just feed a new supply from a front positive battery post and perhaps for the switched ignition circuit hot wire a cable to the cigar lighter feed with the appopropriate inline 7.5 amp fuse.

The red cable (switched ignition) in the Leonardo 175 diagram suggests it goes to the ECU but I have followed it to the emulator and perhaps from here it goes to the ECU? Not unravelled the sheathing to check this.
Any reason why the switched ignition should not come on when ignition switch in position 1 rather than pos 2 ?

[rossko]

Off topic, RR ABS -
http://www.rangerovers.net/repairdetail ... lator.html

[Gilbertd]

So your P38 brakes require air pressure stored in a tank similar to a bus or a truck for assisted braking ... is that standeard oem or a modification ??

As Ross has kindly linked to the full description, I won't bother. But no air involved at all, it's fully hydraulic and very similar to the system used on proper Citroens. The pump pressurises fluid into a pressure accumulator (a sphere with a membrane with Nitrogen under pressure on one side and fluid on the other) which is released when you press the pedal. It feels slightly odd when you first use it as the pedal is pressure rather than movement sensitive so it doesn't have a lot of travel but it certainly does a good job at stopping over 2 tonnes of car!

[Stuzewheels]

OK I give up!

Lets change the thread subject.

I'll get there eventually no doubt - lol

[demonicwillow]

Returning to the thread issue, I suppose if I can't seem to find the trail of the two power supplies to the Leonardo ECU I can just feed a new supply from a front positive battery post and perhaps for the switched ignition circuit hot wire a cable to the cigar lighter feed with the appopropriate inline 7.5 amp fuse.

The red cable (switched ignition) in the Leonardo 175 diagram suggests it goes to the ECU but I have followed it to the emulator and perhaps from here it goes to the ECU? Not unravelled the sheathing to check this.
Any reason why the switched ignition should not come on when ignition switch in position 1 rather than pos 2 ?

If your cigar lighter is switched on by turning the key then there shouldnt be a problem because the system will turn off, however if the cigar lighter power is still on with the key in the auxillary position then I personally wouldnt advise connection there as when you turn the engine off the lpg system would still be effectively on, you would be better to find an ignition only switched feed which would turn the lpg system off even when the key was turned to the auxillary position, connection to the battery + for the permanent supply is ok providing you have the correct 7.5amp fuse

[Gilbertd]

Auxiliary (key in position 1) almost always goes off when cranking, you need a supply that stays on.

[Stuzewheels]

Auxiliary (key in position 1) almost always goes off when cranking, you need a supply that stays on.

Thanks I'll remember that.
Got to trace why my permanent supply to unit now seems no longer connected. Must be something to do with my cutting out what I thought was irrelevant wiring to the Carphone system at back of radio. It was like spaghetti junction behind there. Is it likely the permanent supply would have been linked to the radio perm live? Independant would seem safer.

Will have to do the upsideown bit on drivers seat, if my back will suffer it, to find that switched cable route!

[rossko]

Is it likely the permanent supply would have been linked to the radio perm live?

Is there any way we could guess that !!

Good luck with the looksee, hate getting head backwards under dash, usually makes me sick.