Hi Everyone,
Some of you may recall from an old thread the problems I've had with the tick over on my discovery. After many attempts to put right eg cleaning or changing the stepper motor, changing the air flow metre and numerous goes at adjusting the idle speed with an alan key the problem still exists. Lately its struggled to start, which I put down to a defective battery( after many attempts the battery would make a constant clicking noise ) today, I fitted a brand new battery, still can't start the vehicle. Any ideas?

Besides not starting what's it actually doing? Does it sound like it trying to start or not?

When running is it hunting, misfiring etc

Prior to me replacing the battery, it was turning over but not firing. It was the many attempts to start it I think I flattened the battery.

hughesey said:

Prior to me replacing the battery, it was turning over but not firing. It was the many attempts to start it I think I flattened the battery.

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is there a spark at the plugs?

is there fuel at the injectors?

Invest in some inline spark testers and check you've got a spark.
The ignition system is dead simple so it's best to start there.

If you've got spark test the valve at the fuel rail for fuel pressure next - just watch your eyes!

hughesey said:

Prior to me replacing the battery, it was turning over but not firing. It was the many attempts to start it I think I flattened the battery.

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Charge the battery then get an assistant to help:

Remove the king lead from the dizzy cap and hold it close to a good earth (Use insulated pliers to hold) then get your assistant to crank the engine over - you should get a good fat spark. If no spark then check coil and ignition amplifier.

If you get a spark issue likely to be rotor arm. But check for spark at plug; remove a plug, attach it's HT lead then ground the plug and crank the engine, if the plug is sparking then you need to check for fuel. If no fuel you will need to investigate the fuel pump, if this is working then you'll need to look at ECU - check earths as injectors are earth switched. Also check inertia switch is closed.

If you have fuel and sparks the engine is probably flooding - you'll need to remove the plugs, disconnect the ecu then crank the engine and then leave it for 10 -15 mins. Dry and clean the plugs then put them back in. Release the distributor clamp so you can turn the dizzy. Reconnect the ecu, get your assistant to crank the engine while advancing the distributor, this often is enough to get it running. If you can get it to fire you will then need to set your ignition timing. Remember to mark the position of the distributor BEFORE you slacken it off and move it so you can put it back where it was if need be.

Do a search in the V8 section, lots of info on how to sort starting problems. If you have been adjusting the air flow meter, chances are the CO trim will now be out, again do a search in the V8 section you should find what you need to set CO trim IIRC it should be 1.8v for CAT and 1.0 - 1.5v for non-cat.

HTH

Thanks Guys, problem solved. Apparantly is was a faulty connection on the coil. New connections fitted fine now. Another on going problem is with the idle speed, one minute it will tick over at 750-800 rpm then it would drop to just below 500rpm amd sometimes cut out, suggestions??

Set the throttle plate with a feeler blade, check that the vacuum advance is working ok and that the mech advance isn't seized or sticking, check for air leaks in the inlet manifold and check your coolant temp sensor.

hughesey said:

Thanks Guys, problem solved. Apparantly is was a faulty connection on the coil. New connections fitted fine now. Another on going problem is with the idle speed, one minute it will tick over at 750-800 rpm then it would drop to just below 500rpm amd sometimes cut out, suggestions??

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Get yourself over to the V8 section and do a search, but in no particular order I might suggest the following:

1 - Check ignition timing.
2 - Check base idle.
3 - Check/clean stepper motor.
4 - Check throttle potentiometer.
5 - Check for inlet air leak.
6 - (A long shot but...) Check alternator output and battery voltage.

Thanks for that, I'm not the best mechanically so I will take it to the local independent LR for a diagnostic. Better re-mortgage the house, and watch this space there could be a Discovery up for grabs.