[v8volvo]

Check out an older VW and you'll see that that's how they work. IDI diesels really need glow to start even when they are somewhat warm so I can see how even a pretty sound D24T might crank for a longer period of time under certain circumstances, given the design of the Volvo system... but it shouldn't be too long.

An IDI diesel with good glow plugs and a good battery will start from cold even if it has very low compression. Witness my '85 744, which will not start *at all* when lukewarm unless you manually power up the glowplugs, but starts perfectly from cold every time. I had an old Rabbit with almost no compression until I rebuilt it. That also started perfectly from cold with good glow plugs, even though it went through a quart of oil every 100 miles!

A TDI won't use the glow plugs at all until the temp gets down below about 47F. Check it out with a test light next time you work on a TDI (at least an older one, up to 2003 or so) and you'll see this is true. Direct injected diesels are a completely different animal. They will start under most conditions without any glow, period. You can disconnect the plugs on a TDI and it will still start even if it's below freezing out (yeah it will be smoky and rough, but it will start). IDI diesels are the opposite -- they NEED the plugs when cold or they won't even try to start, and as you found out, they sometimes need em when warm too.

The difference has to do with the ratio of combustion chamber surface area to volume, which is much higher on an IDI than a DI, resulting in much more heat loss to the surrounding metal parts (cyl head, prechamber, piston, etc). That's the same reason why a direct injected diesel has higher efficiency than an IDI one, if all other factors are kept constant, and why the manufacturers were able to make the glow time so much shorter on diesel engines once they switched to DI.