Hello , been having a read up, the system is bosch cp 3 twin point control , with inlet metering valve in pump and drv (diesel regulating valve ) in end of rail .
My heads going a few ways and without proper test gear we can not prove some of the diagnostic pathways .
On the graph of the non start i can see that the pressure is sat at around 80 bar but the inlet metering valve duty is going up trying to get rail pressure to go higher but its not responding , this could be because of injector spills being excessive or poor high pressure pump or the drv in the rail is leaking off rail pressure or imv sticking , so without the bosck kit for capping off the drv or checking spills , or checking low side pressure as ive already said we cannot fully rule these things out .
I have spoken to a good diesel guy i know and he does say that 200rpms for cranking speed is around what you should be looking for and a starter that is taking to much current draws alot of the residual voltage down so all the ecms are starved of voltage which does not help with start up .
The wiff off easy start just gives the engine a cranking boost and gets the motor spinning faster helping the pump generate more pressure .
Now if we wanted to do cranking and battery checks a inductive amps clamp is a good tool , we could put it around the heavy starter cable and see how many amps are being pulled out and look at battery volts also .......if the amps goes really high we could say the starter is drawing to much current and this also would show that the battery is capable of delivering that current and the volts stays above 10 volts whilst under continuious cranking this is showing the batterys good , if the current draw was not that high but battery volts drop alot when under cranking we can say the battery is poor.
So like already said we could be looking at a bad starter ......but with these vehicles now doing a starter could be an epic task so with diagnostic pathway tests you do not need guess work ....just the correct kit ........test not guess ..... work with this mantra ...... " what if i fit x or y and it does not fix it ...then what ? "
As a repairer we cannot guess with customers money ....although most of the garages do just that ...... we call it " firing the parts cannon at it " and hoping you fix it ......... what happens when you have fitted a load of parts and its still the same .......then what ??
Going off on a tangent here , we have a 61 plate discovery 4 in just now 3L diesel, fault code for crankshaft sensor keeps flagging , ive scoped this to death to prove this fault ,as to do the job the body has to be removed from the chassis then engine pulled out to remove passenger side turbo to get at the crank sensor ( superb design eh ? ) £55 for the sensor , around £3000 labour so we have to be sure .............
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