Cold start, engine runs for 3 seconds

Strange problem on our newly acquired TD5. Starting from hot and once its going absolutely no problems, but intermittently (every other day) from a cold start engine fires immediately and runs for exactly 3 seconds, then appears to just switch off, no misfire just turns off. When trying to restart it doesnt fire at all. Sometime later it will start and run perfectly.
Fuel pump runs OK, Brooklyn changed fuel pump relay and it worked for 2 weeks and now fault is back.
Also noticed that when it fails to start the glow plug light does not come on, leaving it for 5 mins and faffing about looking for loose wires noticed that after glow plug light comes on then the engine will start - sometimes it then cuts out again, - exactly 3 seconds. Eventually it start and runs fine..... 'till the next day. Once engine has run it can be stopped and restarted fine.
Checked fuel pump (cant be this as there is no bad running at all, and you can hear the pump).
Checked pump cut out switch, pump relay changed.
WOndered if it could be something to do with the immobiliser??
Or is there a circuit associated with the glow plugs and relay that controlls power to the ECU.
Any ideas appreciated, to help here thinking of buying a fault code reader - anyone have views on whats the best (affordable for DIY). ??

Bill_H said:

.....thinking of buying a fault code reader - anyone have views on whats the best (affordable for DIY). ??

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Hawkeye........the best tool for that money.......and it covers everything on a D2.......most generic fault code readers are covering only the engine management and eventually the ABS .......will come a time when u'll need to scan the rest of systems, especially the BCU(unfortunatelly that's unavoidable on a Disco 2.

Sounds like a sticky glow plug relay. Please state auto details (model, make yr, etc.) so can look into relevant circuit diagrams.

Try closing up the contacts for the ECU load relay and the fuel pump relay - the relays might be OK,but the connections may not be.Forget the glow plugs,once its fired it should stay going.Also unlikely to be immobilisation issues.If the relay sockets are good then I'd try subbing over an ecu,TD5's are starting to show up age induced faults now.....

Thanks for all the suggestions. It went wrong solidly for an hour (in the middle of the country just as it was getting dark). No diagnostics avail so tapped everything - especially all the fuses and relays. No joy, gave the fule pump isolation switch a sharp thump and didnt notice that it tripped - so spent next 30mins trying to work out why the fuel pump stopped running......, remade the isolator and back to original fault. Then suddenly it all worked and has now run faultlessly for 2 weeks.
SO, I made up a little box with some 12v LEDs and attached them to a variety of leads at the ECU - looking at main power to ECU, output of glow plugs AND the green/white lead that the Haynes manual says - To ALARM NOT SHOWN.
Everything looks as it should as the cars running, but the alarm LED flickers badly. The ECU appears to need 12v on pin 34 on C658 on the ECU (black plug). Im guessing that this may well have something to do with the problem, perhaps a bad connection - if that voltage disappears I think that the ECU is disabled as part of the theft prevention.
So to the question....
Where is the alarm control box - and does anyone have the circuit diagram showing where that green/white wire goes?
I need to get a voltmeter to the other end and trace the circuit for a bad connector.
Haynes manual shows no further detail of the alarm system.
Its a Defender TD5 on an 05 plate, actually my daughters car - Huge wheels, Warn winch, Ifor William tow bar and Snorkel. I never realised how good a Defender looks when loaded.

Well, its worked fine now for 3 weeks and now the faults gone solid.
Cant get it going at all, need to get it recovered..
Interesting the LED I attached at the ECU to monitor the alarm now is on solid - no flickering as before. SO symptoms again are engine fires and revs OK for about 3 seconds, then just turns off. If you try to start immediately the engine does not even fire, but if you wait about 20 seconds for the main relay to drop it fires OK and runs again for about 3 seconds.

At a complete loss now, anyone got any ideas? Im really suspicious of the immobiliser,

Bill_H said:

Well, its worked fine now for 3 weeks and now the faults gone solid.
Cant get it going at all, need to get it recovered..
Interesting the LED I attached at the ECU to monitor the alarm now is on solid - no flickering as before. SO symptoms again are engine fires and revs OK for about 3 seconds, then just turns off. If you try to start immediately the engine does not even fire, but if you wait about 20 seconds for the main relay to drop it fires OK and runs again for about 3 seconds.

At a complete loss now, anyone got any ideas? Im really suspicious of the immobiliser,

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Have you tried cleaning the earth connection under the drivers seat near the ecu?

It's also worth pulling the fuses out and pushing them back in one at a time to help keep the connections clean.

I know that you said it seems like it's a fault with the larm ecu judging by what you're seeing with the LED's but I'm wondering what the chances are of it being a crankshaft sensor fault.

Have you managed to get it plugged into a diagnostic computer yet?

Finally fixed it HUGE cost. Main dealer.
This is a really interesting fault and I imagine it will be useful to someone - so heres the fix.
It was the immobiliser turning the engine off.
Engine ran too clean and without misfire to have been any sensor broken, so when we finally decided it was the immobiliser - it was recovered (3rd time) to Hunters the main dealer. They spent a good couple of days on it before diagnosing an open circuit wire between the immobiliser and the ECU.

So the details, I dont think me posting this will make a Landy them more vulnerable to theft - as you cant do anything to bypass this.
There is a wire (green /Grey) that runs from the immobilser to the ECU - this provides a coded signal to the ECU telling it that the immobiliser has been deactivated. Apparently the immobiliser turns off the starter and fuel pump thus preventing starting - but then allows the engine to run for a few seconds while it waits for this coded signal. (My earlier experiment with the LED showed this as flickering), this wire runs through a plug/socket just by the nearside bonnet hinge - and I think its here that we have a bad connection. At this point we have a wire trailing across the floor between immobilser and ECU - so will make good when weather warms up a bit.
Just to be clear - this wire does NOT bypass the immobilser - it just connects the immobiliser to the ECU so you still need the correct key fob hanging next to the steering column.

We had the same problem with our disco II turned out to be oil in the engine loom from the injecters running into the engine ecu.That ran for a while then cut out also no glow plug light.Looked like there was a oil leak o/s front this was the oil running from the looms and ecu.

Phil.