The first of these is a decent battery. Sometime before the winter comes, Check the battery charging voltage. If it isn't getting to 14 Volts or more with the engine idling, then either the alternator belt is loose or the olly itself is low output.
Paris Rhone alternators can be removed and the black brushgear and cover may be removed with nothing more than a screwdriver. Check that the Lucar terminal is tight (the thin wire that plugs in) and that the post terminal is clean. Once the brush gear is off, check it all for wear and give it a good scrub.
The connector that makes to the alternator body may be corroded as may the nuts either side marked b+ and b-. Take them off, clean the nuts, posts and washers with a wire brush as well as the alternator mountings. Ensure you have a good half inch of brush left.
Reassemble the lot and consider fitting a cable from the alternator to the battery directly.
Remove the engine earth from the engine at the gearbox before cleaning it up and replacing it tightly.
Now check the battery terminals and if they are not in good condition, replace them. Replace the battery every three years with a good one.
A precautionary clean of the starter motor brushgear every couple of years will save you from trouble there but they rarely fail.
Assuming that the fuel lines are tight and not leaking air which causes fuel to run back to the tank, (And in turn, wasted energy pulling up fuel on the starter,) the next problem to avoid is that of the glowplugs.
You will need a meter for this. Power the car up and listen. Once the light goes out, the glow plug relay holds in for another ten seconds or so. (If your battery is weak, wait until it drops out before attempting to start up. The plugs will be hotter and there will be more power available to spin the engine.) once the relay is in, check that the voltage is getting to the plugs. You should see 11 or more on the wire linking the tops of the plugs if you have a well charged battery.
If you are dropping more than 2 Volts between battery+ and plug, then strip and clean the blue glow plug relay terminals and if necessary the contacts themselves.
Rough running after startup, coughing and smoke etc. is usually down to a duff glow plug. To find out which one, simply remove the feed cable from the tops of all the plugs and measure the resistance of each plug with the meter. They should all be about the same, under an Ohm. Any that are much higher will be faulty.
That really is all you need to know
With Thanks to Tom for the above write up.
(watch the dash lights after the light goes out for approx 10 seconds) they will get brighter
