You know the maddest thing ever, as you mention glow plugs....?
My dci was very hard to start for a few days a few months back. Long story short. Bought 4 glow plugs off
for £17, fitted them. Bought a leak off kit for £25 on
, tested with it & no issues found.
Never a problem starting since. Wierd.
In general terms, old style diesels with indirect, pump timed and the like injection, needed glow plugs to start when cold. Without that concentrated heat, they was bu55ers.
DCIs generally do not need glow plugs to start unless temperature is down around zero. Higher injection pressures, better compression, better atomisation of fuel all contribute to better starting.
They only operate at full wack for a few seconds, then either turn down or off. Main purpose now is emissions control as a cold engine does not burn fuel as efficiently as a hot one.
If an engine is getting old, maybe lost a little compression, they still help starting so is worth swapping for the cost they are. Or at least checking.
My gripe is that many garages still stick to the "not starting, swap glow plugs" from older days.
By the time they have included labour costs it costs the motorist a lot more then 17 quid from
and often does not solve the problem.
To me it is same as the mandatory diagnostic charged by dealers. Often unneeded but "must be done"