GEMS 4.0 - Check engine light on at key on - ECM OK?

Ok, i've asked this in my other thread but no one has answered so can i have a definitive answer to this please?

GEMS ignition 1995 P38 4 litre V8 Range rover

With the key on and in position two the check engine light comes on, does this mean that the immobiliser is disabled and the ECM is in sync with the BECM?

It does mean engine ECU and BECM are in sync, but not that immob is off, further turn of key either starts it or gets Engine Immobilised, Press Key Fob message

Ridesafe said:

It does mean engine ECU and BECM are in sync, but not that immob is off, further turn of key either starts it or gets Engine Immobilised, Press Key Fob message

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Awesome, i get no engine disabled / immobilised etc when turning over so i guess i'm not looking at an immobiliser / sync issue..

I have key fob issues but the prev owner had these when it ran.. another question, if the immobiliser is armed or the BECM is out of sync, will it spark?

Cheers for the help

From the sound of this there are no immobilisation/synch problems.If the CEL comes on and it cranks,it should go.Loss of synch with Gems will inhibit CEL,sparks and fuel.
The Gems ecu should provide an earth path to pull in the fuel pump relay for a couple of secs when turning to key two,then continue when the engine starts.Unless the inertia switch is tripped the conditions you describe should make it work.Basic electrical checking on the wiring and relay should prove if its all good.The injectors are also individually provided with an earth path from the ecu to open them - again basic checking.

eightinavee said:

From the sound of this there are no immobilisation/synch problems.If the CEL comes on and it cranks,it should go.Loss of synch with Gems will inhibit CEL,sparks and fuel.
The Gems ecu should provide an earth path to pull in the fuel pump relay for a couple of secs when turning to key two,then continue when the engine starts.Unless the inertia switch is tripped the conditions you describe should make it work.Basic electrical checking on the wiring and relay should prove if its all good.The injectors are also individually provided with an earth path from the ecu to open them - again basic checking.

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did you say you was in reverse then is stalled, there is a switch that turns the fuel pump off if it detects a heavy bump or acident worth checking and resetting if its triped

eightinavee said:

From the sound of this there are no immobilisation/synch problems.If the CEL comes on and it cranks,it should go.Loss of synch with Gems will inhibit CEL,sparks and fuel.
The Gems ecu should provide an earth path to pull in the fuel pump relay for a couple of secs when turning to key two,then continue when the engine starts.Unless the inertia switch is tripped the conditions you describe should make it work.Basic electrical checking on the wiring and relay should prove if its all good.The injectors are also individually provided with an earth path from the ecu to open them - again basic checking.

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I havent checked the inertia switch but from what i've read it gives a message when it has so i'd have noticed that..

The fuel pump doesn't seem to be working, i swaped the relay with the starter relay and it still cranked, so the relay's ok. The fuel fump relay definately clicks on at key on but no fuel at the pipe and no noise from the tank, i'm just wondering whether this could also explain why the injectors arent firing, a colloeague said if there's a pressure switch/sensor on the rail it's likely that it's not firing the injectors because there's no fuel pressure..

I'm just wondering whether this is likely? Either way i need to get the tank off to check whether the fuel pump problem is the pump or the wiring, which won't be until the weekend... Might just order a pump off fleabay... i can always sell it again if it doesn't work.. :flame:

1, There is no pressure switch on the fuel rail,just a temp sensor.
2,How are you sure the injectors arent opening ?
3,Dont waste money on a fuel pump until you have tested it.
4.I cant remember if the inertia switch tripping is supposed to put up a message on the dash - but I certainly wouldnt rely on it working properly if it was.

From memory the live feed to the fuel pump is a purple/white wire,after checking the inertia switch is closed why not check for power in the loom where it goes throught the grommet under the carpet over the tank.Dont forget the pump needs to be earthed as well.I have seen the pump wires chewed off by mice/rats.Rather than dropping the fuel tank to get at the pump many people now cut and peel back the floor under the carpet - now the P38's are worth less its a good option - esp if you dont have a ramp.

eightinavee said:

1, There is no pressure switch on the fuel rail,just a temp sensor.
2,How are you sure the injectors arent opening ?
3,Dont waste money on a fuel pump until you have tested it.
4.I cant remember if the inertia switch tripping is supposed to put up a message on the dash - but I certainly wouldnt rely on it working properly if it was.

From memory the live feed to the fuel pump is a purple/white wire,after checking the inertia switch is closed why not check for power in the loom where it goes throught the grommet under the carpet over the tank.Dont forget the pump needs to be earthed as well.I have seen the pump wires chewed off by mice/rats.Rather than dropping the fuel tank to get at the pump many people now cut and peel back the floor under the carpet - now the P38's are worth less its a good option - esp if you dont have a ramp.

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I stuck a multimeter across the pins on one of the plug and cranked it, no needle deflection so no signal...

The pump relay doesn't cut out therefore i'm assuming there's a pressure switch somewhere to tell the pump when to cut out at key on?

i would have a look at the cps, as that would stop you getting fuel from the pump.. just thinking out loud..

IT'S ALIVE!

Only on Gas, but still - good start to the weekend!

j the range said:

i would have a look at the cps, as that would stop you getting fuel from the pump.. just thinking out loud..

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Crown prosecution service? The buggers meddle in everything.

rufusw5 said:

I stuck a multimeter across the pins on one of the plug and cranked it, no needle deflection so no signal...

The pump relay doesn't cut out therefore i'm assuming there's a pressure switch somewhere to tell the pump when to cut out at key on?

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NO ! There is no pressure switch ! just the ecu controlling the earth side of the fuel pump relay.

eightinavee said:

NO ! There is no pressure switch ! just the ecu controlling the earth side of the fuel pump relay.

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That makes sense.. It probably cuts the pump when it starts to draw current over a given threshold... I know the relay doesn't click off until there's pressure so there must be something!

I think you are trying to over complicate the issue - the Gems ecu just provides an earth under controlled circumstances.I dont think it can monitor the fuel pump current like the Becm can for say window lift motors as an anti trap function.
My info comes from a factory SIDS,(Systems information document) which is far more detailed than the dealers RAVE info - I dont recall any current monitoring in any of the Gems stuff - just fuses for circuit protection.
I still think there is a simple wiring fault,asc these cars are ageing I see more and more corroded wires that are not easy to spot.