I bought a 1984 Jetta 1.6TD GL today (my first watercooled VW) with one perplexing issue:
The car starts great when cold. Like, three cranks and it lights right up. However, when it is warm (thoroughly warm, run for an hour) and then shut off, it really need partial/full throttle and the cold start lever to give it a chance to fire up. Furthermore, it doesnt really start great when it does fire- it takes a couple seconds to fire in all four cylinders. Once it is running, it runs great again.
Any ideas why this is? It seems like the polar opposite of a worn out diesel. The pump timing is set correctly (recent timing belt). True mileage is unknown but the body and engine are both far too good to match the 390k reading on the odometer.
My one theory is that the glow plugs aren't running when it is warm. I noticed this today when trying to get it to not start. From cold, the light comes on and stays on for a little bit, and then goes off. When warm/hot however, the light never comes on! Could this be the culprit? (read here??:
http://www.vwcaddy.com/showthread.php?50377-Engine-Temp-Sensor-Glow-Plugs-out-when-warm)
Is it as simple as this, or could it be something to do with the ignition switch or wiring?
James