Intermittent failure to start enging

Hi,hoping someone maybe able to shed light on this problem.
We have friends who have a Mercedes Sprinter 316cdi SWB, an ex-ambulance,
here in Australia.
They have experienced intermittent failure to start.
An [F] light shows, no sound.
They leave it for 30minutes and then it may or maynot start.

jem&scout

Ambo's have a different assist to normal sprinters
F can you clarify is it on the dash with an icon showing !!!or is it showing K in the kilometer section ?
PS what year is the Sprinter the production date is on the drivers seat side nearest to the drivers door and on compliance plate left hand side left inner guard above battery.
Will look at a local ambulance to night to see what it may be
Richard

thanks for the reply altered sprinter.... we spoke to our friends last night and here is the condensed version of their problem with their 2004 model 316 cdi Mercedes Sprinter...
there are 2 seperate issues...
No 1. When turning the key the engine won't crank, but the gears will select up through the range. ( 6 speed triptronic )
No 2. With the ignition key on to start, no crank, but (F) shows in the centre of the dash in the yellow portion.
When fidling with the relays under the drivers seat may correct the problem but not every time.
Any help would be grateful...
Jem&Scout

OK I'm in part with it now I think My year 2003 Plated your Friends van is on an old version of C bus electronics, there may be a wiring problem from cutting and shutting or to be nice the wires were Left bare for auction resale.
six speed triponic manual-auto sprintshift sorted that one.
I will get the book from the local ambos today... and look up F ? sounds abusive have no idea what this is though! sounds more like a failed Glow plug if its not starting , but leave it with me untill.. to night.
Richard

jem&scout
Please accept my apologies for delay been busy.
I have been to Mercedes to check out the code as to different systems used in Australia and as to some running digital full time and some on part digital-and analog.
The answer from Mercedes was fault code not recognizable incomplete information.
Because you have indicated playing with the electronic box and sometimes it appears to free up what ever the cause this is the information ..I have been given
Code..P 0600 Can to Can data base Bus circuit fault.
HKpeice just ran a full code listView attachment Sprinter-DTC-P-Code-List.pdf it's not a system that is fully used with Sprintshift or as to fuel bar sets be careful with the diagnostic code- NOT AUSTRALIAN- but this should assist your Friend in-sorting out what may be wrong
In conclusion I would take this back to Mercedes -Benz to have electrics fixed and a full diagnostic scan to adjust to perfect running conditions.
Have a Nice Day
Richard

Altered Sprinter, thanks for getting back to us and thanks for the info. Will pass it on to them when and if they get back from their week long trip to Canberra. Will let you know what happens. Regards jem&scout

jem&scout..Your welcome hope it helps.
Richard