Just a guess, but if one or two pre-heater plugs were inoperative you would,
presumably, have unburned fuel in those pots and blipping the throttle a few
times would clear it out enabling normal compression ignition to start.

Hiya Phil

In my experaince, I have a 405 with 250,000 on the clock, it's either, air
getting in through the fuel pump, or the injectors may be be going (1 off
them can cause the problem).

I have the same problem, it really bad in cold weather, but once it's warmed
up its ok......

It maybe the pump itself, but this depends on the milage and it very very
costly

Hope this helps

anton