It is straightforward, but:
Dry lube the Bendix as they stick if they have grease on.
You will need quite a lot of battery cable and ends as the cable has to go from the battery to the solenoid and back to the starter. Make them up and solder the ends on.
You can use these from Toolstation:
https://www.toolstation.com/copper-tube-crimp-lugs/p11930
They are 16mm2, I seem to recall sawing a split in them and opeing them up to fit the cable, then crimping and filling with solder.. If you are struggling to get the cable you can use welding cable, the current rateing needs to match the CCA on the battery which is probably around 500A on a petrol but its only for a few seconds. The cheap way is to go to a breakers and get a car with the battery in the boot and pull the leads out, we used to use Minis but I think some Mercs do now and you may get the ends on already.
Tie it in place, it feels stiff but it gets warm when you are cranking and can sag.

thspeller said:

That’s very interesting jamesmartin. I’ve uploaded a photo of the starter. See what you make of it - I assume you’re saying that the engine probably isn’t original to the car therefore. I’m new to landy’s So god knows what I’ve bought (). The starter is a Mirelli M78R. I’m going to try pluck up the courage this weekend to take it out and try see if I can find the problem. Thanks againView attachment 165907 View attachment 165908

Click to expand...

thats an after 1980 5 bearing engine so not the original, which is no bad thing
get a length of wire fit a female spade terminal fit that on the solenoid trigger wire location, then touch the other end to the terminal were main battery cable connects, if starter works its an issue between ignition switch and starter if it just clicks its a starter issue
you cant fit an inertia starter only the pre-engage type as fitted, teeth on ring gear are opposite way round, pre engage solenoid pushes starter gear into mesh , inertia the starter gear come in from the rear

All, thanks for all your advice so far. I have just completed my first bit of landy surgery and removed the starter. Developments are as follows: (1) my series 3 has a 1983-85 2.3 petrol 5 bearing engine (code 11H) from an early defender; (2) it appears that the Lucas M78R starter (which I have) is indeed the correct one (see attached); and, I now need to find out where the problem is.

So, what I am considering doing is. First, test the starter by running jump leads direct from the battery to the starter. If that doesn’t work, I’ll replace the starter.

If the starter does work, it’s time to replace the cabling from the battery.

If anyone can confirm this is the right course of action, that would be great.

Thanks for your help and patience with a beginner. Am loving it though!!

If the motor run's direct from a battery I would change the solonoid swtch,a common enough problem.

It all comes apart. If its the motor then its usually a dirty communitaor or stuck or worn brushes. The commutator is easy to clean (look on google) and the brushes are a few £. The soleniod may or may not come apart, some are screwed and some rivetted but you can sometimes drill the rivets out and put screws in. Part of owing a series is learning how to strip all the components and refurb them rather than replacing as unit. To strip and replace the brushes / polish commutator on the starter is about 2 hours work (max) once the starter is on the bench, 2nd time (if there is one!) it will be 30 mins.

Changing the solonoid on your motor is straight forward,disconnect electrical wire's, undo the two small bolts and pull off. Watch for the spring falling off the piston and remember to replace it.

Thanks All - Now fixed. Leaking rear oil seal had caked starter in oil and whilst solenoid engaged starter cog to fly wheel, it wasn’t spinning. New starter, job done.