Runs ok on gas but not on petrol now HELP!!!!!!

Bigmatt · Post by **Bigmatt** » Thu Feb 22, 2007 5:01 pm

Hi, im new on here so apologies for any mistakes etc but i really need help with my rangie 3.5 efi v8. I fitted an lpg system to the car bout 8 months ago and its been perfect till bout 3 months ago when its stopped running on petrol. It initially fires but then stalls n dies yet on lpg it starts and runs fine. Ive replaced all the relays with new, disconnected the gas kit completely, tried new airflow meter, new ecu - all no difference. Ive had it to a mechanic who says the fault is that the injectors arent getting the signal to switch on but that would be down to the ecu which has been replaced. Does anyone have any ideas or perhaps come across the same problem before? I need help!

Cheers very much

Matt

softdash3.9 · Post by **softdash3.9** » Thu Feb 22, 2007 6:25 pm

Here's a few pointer for starters

Is there petrol in it?

Has the petrol side lost its prime due to lack of use?

I know it may sound daft!! Has the petrol gone stale due to age?

Is the fuel pump running?( if you remove the air cleaner, turn the ignition on, and open the flapper inside the airflow meter the you should here the fuel pump running)

Pump can die if its been runing with no fuel.

If it has lost its prime sometimes the relief valve sticks and you can't purge the air back to tank.

Does you LPG system use emulators that interupt the signal to the injectors? Is it a vapour kit? e.g. gas ring on inlet

Hope the info helps

ChrisJC · Post by **ChrisJC** » Fri Feb 23, 2007 7:55 am

A flapper EFi firing then dying is a classic symptom. This happens when the ECU doesn't think that the engine is turning.

The engine fires on the 9th fuel injector (cold start mechanism), and then the main ECU should take over, but it doesn't.

The reason for this is usually that the spark feed signal from the coil which goes through the overrun cutoff relay to the ECU is open-circuit somewhere. It probably also goes through some part of the LPG conversion so the LPG system can cut off the petrol when running on gas.

So check that the overrun cutoff relay is working properly, and that however the LPG system cuts the signal is also reconnecting it!

Chris.

Bigmatt · Post by **Bigmatt** » Fri Feb 23, 2007 10:41 am

Hi again, thanks a lot for the helpful tips, there is 3/4 of a tank of petrol and ive drained it and put fresh in, still no joy. there is fuel at the fuel rail and that side is fine im told so i think the relay side sounds more hopeful. next question is do you no where the over run relay for the ecu is located and are they in the same place on a 3.5 and a 3.9 engine?

Again thanks a lot for the info hopefully ill be able to get it sorted

matt

softdash3.9 · Post by **softdash3.9** » Fri Feb 23, 2007 8:58 pm

If I remember correctly the relay is near the air flow meter, the vacuum switch that operates it is on the rear of the inlet plenum, so trace the wires to the relay

Could remove the relay and bridge the circuit with a piece of wire in the short term to check

ChrisJC · Post by **ChrisJC** » Mon Feb 26, 2007 8:14 am

There is no cutoff on the 3.9 as far as I know.

The cutoff valve is right over injector no. 8, you can just link the two wires together. The relay is near the coil / AFM, you can bypass that too. It's got a black / white wire coming out which goes directly to the coil.

Chris.

Post by **Rossco** » Mon Feb 26, 2007 7:46 pm

Check all your vacuum hose for any splits.

Bigmatt · Post by **Bigmatt** » Thu Mar 01, 2007 9:43 am

Hi guys thanks a lot for all the info, ive sorted it. I turns out that it was the wire from the switch on the back of the plenum chamber to the relay that was open circuit! We replaced that bit or wire yesterday n instantly its all fine, im absolutely over the moon, its bein MOT'd on fri n then im back in business. Just wanted t say such a big thanks cause it was drivin me nuts, cheers again.

a very happy big matt!!!

softdash3.9 · Post by **softdash3.9** » Thu Mar 01, 2007 6:11 pm

Another happy member

Glad the info was useful

Greybeard · Post by **Greybeard** » Wed Mar 07, 2007 8:56 pm

First, thanks for helping my friend Matt, but i have the same problem on an hotwire system.

Anybody shed any light please.

Thanks
Steve

ChrisJC · Post by **ChrisJC** » Thu Mar 08, 2007 7:56 am

Out of my league - never played with a Hotwire.

Try to get hold of the Land Rover diagnostics guide - they're pretty good!

Chris.

jwriyadh · Post by **jwriyadh** » Thu Mar 08, 2007 8:12 pm

It's worth checking the same cause, ie, lost coil signal. In the case of hotwire there is no relay, the connection from the coil negative terminal goes direct to pin 39 of the ECU with a 6.8k ohm resistor inserted in the wire usually near the ECU end of the injection loom.

Also worth turning on the ignition and checking that battery voltage is available at one of the pins of the injector connector plug.

If that connection is good come back with a detailed note of the symptoms.

jw

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