Land Rover Discovery 3.9EFI - no spark

adamnreeves · Post by **adamnreeves** » Sun Aug 09, 2009 12:44 pm

Son bought a Series I discovery yesterday. Done the 80 mile trip plus a few more miles. All seems good. Anyway, he decided to take it a place where they valet the car and clean the engine. Well that's where the problems started.

He called me and said it was missing fire a bit. He said you got the engine jet cleaned. I asked if they took an precautions, i.e. wrapped the dizzy, coil up, etc. He said no! Anyway he called me back then to say the car stopped and will not start!

So car is now recovered home and the RAC man said he reckons its the coil put his diagnositics on it. So I bought a new coil and fitted it and still no joy. The RAC man also said the injectors are not getting a pulse either but might be remedied with the coil being replaced. I thought erm, maybe, the ECU grounds the injectors I thought, so ECU deciding not to switch them on.

This is what I have done so far:

1. checked wiring to coil same as removed, white/black wire to -ve post and black! wire to +ve. The supressor cap is from +ve to earth.

2. check with my timing light on no.1 lead whilst cranking, nothing, repeated for coil lead, nothing.

3. removed +ve writes and remove supressor and checked voltage on igntion on, +6.45volts. This is lower than a thought so check battery voltage, 12 something volts.

does the immobiliser cut the fuel and ignition circuits. negative switching though.

paul c · Post by **paul c** » Sun Aug 09, 2009 10:37 pm

sounds like a wet dissy, usual with Rovers after jetwashing the engine. remove the cap and dry it out is my usual fix.

Robrover · Post by **Robrover** » Mon Aug 10, 2009 8:30 am

Yes, dry the cap out thoroughly. Unlikely to be the spider but it could be as the symptoms are the same. Also could be the amplifier.

Try hot wiring it direct from the battery +ve to the coil +ve and see if it fires. The ECU gets its command to fire the injectors from a wire direct from the coil, so if there's no spark there's no fuel being delivered into the engine either.

adamnreeves · Post by **adamnreeves** » Mon Aug 10, 2009 8:31 am

I did check this and it seemed quite dry. Last owner must have changed it along with rotor arm as it looks brand new.

I checked the main coil lead with my timing light and no HT current is being produced. If the dizzy was arcing inside I would still get a HT current from the coil. I have since checked the current flowing through the new coil in situ and no current is flowing. However there is positive supply to the coil. Only leaves faulty or wrongly supplied coil or whatever grounds the coil is not.

paul c wrote:sounds like a wet dissy, usual with Rovers after jetwashing the engine. remove the cap and dry it out is my usual fix.

Post by **katanaman** » Mon Aug 10, 2009 12:27 pm

the ignition module grounds the coil. Get an LED with a resistor on it and bridge between + and - on coil, turn engine over and you should see the LED pulse. If it doesnt and you have voltage on the + then either the ignition module is goosed or the supply to the module is dead. your unlikely to see anything with a multi meter or 12v bulb as the pulse is too quick. You could use a scope if you have access to one. You said you only have 6 odd volts on the coil, this is far too low. This should be a 12v system if not at a min it will be 9 volt. Dont know where the fuse box is on these cars but if its in the engine bay I would be looking at that being soaked even is it isnt I would check the fuses in case they are corroded which would give you low voltage. Failing that check all the connectors for corrosion/wet and if you want to prove the theory then take a bit wire direct from + battery to + coil which will give you a good clean feed. Your injectors wont fire if your ECU isnt seeing a pulse from the - of the coil as this is where it gets its timing from.
Hope that little lot helps you do some fault finding

adamnreeves · Post by **adamnreeves** » Mon Aug 10, 2009 9:28 pm

Cheers Marki, some bits to check and get on with here.

katanaman wrote:the ignition module grounds the coil. Get an LED with a resistor on it and bridge between + and - on coil, turn engine over and you should see the LED pulse. If it doesnt and you have voltage on the + then either the ignition module is goosed or the supply to the module is dead. your unlikely to see anything with a multi meter or 12v bulb as the pulse is too quick. You could use a scope if you have access to one. You said you only have 6 odd volts on the coil, this is far too low. This should be a 12v system if not at a min it will be 9 volt. Dont know where the fuse box is on these cars but if its in the engine bay I would be looking at that being soaked even is it isnt I would check the fuses in case they are corroded which would give you low voltage. Failing that check all the connectors for corrosion/wet and if you want to prove the theory then take a bit wire direct from + battery to + coil which will give you a good clean feed. Your injectors wont fire if your ECU isnt seeing a pulse from the - of the coil as this is where it gets its timing from.
Hope that little lot helps you do some fault finding

adamnreeves · Post by **adamnreeves** » Mon Aug 10, 2009 11:36 pm

Checked all the relevant fuses were okay. Checked battery voltage with ignition on, was 11.99volts, all this cranking taking its toll on the battery. Measured volt to +ve coil 4.75volts! measure -ve, same 4.75volts. So I suspect wiring so went straight to your suggestion and made up a fly lead with 20AMP wire, proper terminals and an inline 10AMP fuse. Turned ignition on then connected coil to battery. Fired up on first turn of the key, super. Pulled the fly lead off with engine running to see if it would continue to run, just died. I presume this could be ignition key switch or wiring to it from battery and from it to coil, somewhere.

Post by **katanaman** » Tue Aug 11, 2009 11:26 am

Dont know how these are wired but might not be ignition switch as I imagine all that controls is probably a relay which then supplies the fuses and so on. Least you know where the problem lies. It could be something as simple as a dirty connector somewhere or even a broken cable.

Ian Anderson · Post by **Ian Anderson** » Tue Aug 11, 2009 12:05 pm

I had a similar problem - Relay not working right / dirty / coroded contacts or whatever

Replaced relay and it worked.

My relays are behind the seat in the GT40 so cannot suggest where they may be on the original / donor!

Ian

adamnreeves · Post by **adamnreeves** » Tue Aug 11, 2009 12:29 pm

There's a relay in the fuse panel beneath the steering wheel. It clicks on with the ignition so I guess that the one. My first port of call will be to check contacts on this, then the fuse contacts and also in fuse box, then ignition barel. Then the damn wiring! I might end up just running a new lead cable through!

Ian Anderson wrote:I had a similar problem - Relay not working right / dirty / coroded contacts or whatever

Replaced relay and it worked.

My relays are behind the seat in the GT40 so cannot suggest where they may be on the original / donor!

Ian

Ian Anderson · Post by **Ian Anderson** » Tue Aug 11, 2009 3:49 pm

Ignition on I believe activates 3 relays
1 is for fuel pumps
One for this lot and I cannot remember the other!

Ian

adamnreeves · Post by **adamnreeves** » Tue Aug 11, 2009 9:04 pm

Having a right mare with this, so many relays, in the fuse box, in the footwells. I started looking at 1900hrs and it went dark before I could work them all out! The diagram has the imoobliser supplying the +ve to the coil and do you think I can find that, no!

adamnreeves · Post by **adamnreeves** » Wed Aug 12, 2009 9:41 pm

Checked all the relays now. There's only one left I can hear clicking away but this is literally in the middle of the dash looks like I would have to remove it all to get to it. Not going to do that so tonight the landy has a new relay, fuse and a couple of more wires. I basically used an ignition live to switch on the new relay to supply a battery live to the coil. Well it works.