[roKWiz]

A lot depends on where you are and whether the diesel is indirect injected or pre combustion chamber.
Can even depend on the injection pump some inlines struggle while some rotary's just pop straight off.

Glow plugs will certainly help with pre combustion engines.

In areas like country Victoria in Winter most diesels struggle to start without some type of pre heating system.
Sometimes in the dead of Winter here the "Cosby Sauce" might even be needed to due the cold also effecting the battery conditions overnight.

OP should just replace the glows, it being a electronic controlled diesel.