Thread: 300 tdi intermittently wont start

Most dodgy starting can be bypassed by fitting a nice big button under the dash taking current directly from a battery source to the starter solenoid. That way, you're not stuck when it fails to proceed. Then acquire a test light and look for voltage at the key output when you turn the key. After that find the instructions to bypass the immobiliser.

I have just had a look at the solenoid and cleaned the terminals.
It has 12.3 volts at the solenoid power lead with key in start position ( 7.5 with key on accessory?)
With the spade connector/power lead only on the solenoid clicked on and off with the key.
I couldn't recreate the non start state while I had it apart.
The earth from the side of the starter to the chassis is very tight.

If have further problems I might try a test light ( per Beeutey's post) connected to the solenoid.
Then if it wont start but the globe lights then that would indicate solenoid or starter failure wouldnt it?
Or if it didnt start and the globe was not lit then it would mean it was upstream, perhaps indicating an ignition problem. Is this logical?

Sounds like you've got the general idea.

Have you tried changing the relay ?

Originally Posted by trout1105

Have you tried changing the relay ?

Which relay is that?

I am pretty sure that there is a relay for the starter in the engine bay fuse box, that's where it is on my D2a.
It could also be mounted on the starter motor itself.
A dodgy relay would create the problems you are having.

Originally Posted by edddo

Which relay is that?

Easy to find, disconnect the starter motor solenoid wire and have someone move the key to start a few times. You'll hear the relay soon enough. If its contacts are fried the coil will still cause a click sound.

Is the starter motor relay on a 300TDi disco 1 under the glove box on the passenger side?

I always presumed the current went straight from the ignition barrel to the solenoid on the starter motor, but i can hear a click from a relay on the passenger side...

Presumably if the starter motor relay is clicking, the ignition barrel contacts are fine.

I am having a very similar problem at the moment. Out of nowhere it took a few turns of the key to get the starter motor to crank over. But i could hear a relay clicking in the passengers side each time i turned the key....?