Hi there,
Had some similar issues recently and thought I could update fellow bongo'ers and add my findings to this thread...

without hijacking it!
Started to experience issues with the recent cold, damp starts - I usually give it a few seconds after the 5 sec relay light, mostly fires up into life quite quick. Quite a lot of smoke though and a rough idle for a few mins and then ok for the remainder of the day.
So - Got the fuel filer and Glow plugs changed.
Mentioned the glow plug size / busbar mod (possibility) to 1995 Bongo's to mechanic, I had 83mm blue print to replace.
Collected Bongo - Mechanic said he had no worries, the new plugs went in fine and all was good, but the old ones were longer... Not wanting all the gorey details I assumed all should be OK..
All was fine for 8 days, a noticeable diff from morning cold start, immediate smooth idle, alot cleaner on the smoking. Got a good 580km from the next full tank which is fairly good for mine!
Then I tried to start last week and nothing, kept turning over but no igniting...?
He had not been started for 2 days but never been a problem before and the battery fired good.
After a fun day testing a few bits, I have removed the glowplugs to test them - they were very sooty. I could not get them to glow from touching the engine with ignition on?
I then tested battery - that was OK 12 odd V
Checked no18 fuse by steering wheel
Then tested the busbar and this read .02 with ignition on?
(Managed to start the beast late evening today as it’s quite warm i assume - was very smoky! so I assume it’s not the fuel filter)
May I ask some questions......?!
How else can I test the plugs (if I can’t get 12v to my bus bar?)
My busbar is now touching the fuel rail - is this right?
I found the fusewire thingy just off the +ve batt term that goes to the GP relay - How do I test that ?
I am suspecting it could be the relay? maybe, I am not too sure!
I will test that tomorrow
Should my new 83mm GP sit proud from the block - is that a silly one! I have never looked before today!
I am going to call the mechanic and ask some questions tomorrow..
Thanks all!
BFury has been so useful today!
Woz