05/11/2026
using LIVE DATA and DATA LOGGING...
First 2 are fuel pressure the other 4 are injectors... Seeing a discrepancy in a chart ( DOSE NOT MEAN THAT PART IS BROKEN ) reading and understanding how the engine comms work and need will..
ILL EXPLAIN...
1.Desired fuel rail pressure ( what the ECU is saying it needs ) ( purple line on the first 2 photos)
2. Actual fuel rail pressure ( what the fuel pressure is ) ( yellow line )
3. Injector MG/rev ( the calculated amount of fuel injected by an injector into a cylinder during a single combustion cycle )
Now reading just injectors MG/rev ( last 4 photos ) most people would say ohh its a injector or 2 playing up.
⭐️COMMON RAIL vehicles...
fuel pressure and injector MG/rev is ECU calibrated by load.. " load" ( air flow and boost )
More air from (air mass sensor G/S ) more MAP ( Manifold Absolute Pressure ) " normally around 2 to 2.5x the air mass sensor reading.. and finally the boost.. ( boost pressure from the turbo )
More air + more map pressure + boost pressure the ecu then calculates fuel needed on each injectors " injector MG/rev... now the ECU knows theres 4 injectors and each injector needs X amount of fuel pre injector...
The ECU then takes the calculated load of air, manifold pressure boost and injector MG/rev and work out the fuel load needed to keep the injector flow.. ( desired fuel rail pressure)
SOO... Desired fuel rail pressure is what the ECU is asking for... actual fuel rail pressure is what you got..
Desired and actual fuel rail pressure should be the same or the actual fuel rail pressure just under by a very very small bit... ( command then action )
Well the first photos ( purple line is below at the peak ) and injector mg all over the place..
So is it...
•A bad injector ( i dont think so but a injector leak off test will be done to confirm this )
•EGR issues ( maybe ) air load dropping due to escaping out a stuck egr
• turbo wast gate ( possible ) boost leaking past due to a sticky actuator
• HPFP ( high pressure fuel pump ( maybe but again dont think so ).
• a bad rail pressure sensor giving off bad readings ( possible )
• fuel pressure regulator ( possible )
• fuel filter ( no.. first thing we checked )
BEST FORM OF DIAGNOSTICS is not assuming thats the issue ( yeah its normally that on this type of vehicle ) but is eliminating everthing eles it can be to comfirm thats the issue..
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