diesel fuel pump failure or is it pressure regulator

you should never remove anything till you pin point the failure.

if the low pressure pump failed. it starved fuel to the injector or high pressure pump. that alone will burn out the pump.

you said you replaced the lift pump and now have fuel to the injector pump?? then the injector pump most likely has failed.
replace the pump. you wont get credit for the core unless you re assemble it.

Roy

without having the aid of computer diagnostics I carried out a manual test as discrbed earlier and found the resulting fault in the fuel tank but however this has obviously dry run the hpp or an electrical fault has occured to avoid damage.I have not replaced any components as of yet as there appears to be none visibly broken.

you wont see the failure from visibly examining the pump. it is all about clearances and operations.

Roy

The question really is, should fuel go to the c/rail via low pressure pump as it is meant to supply hpp with fuel, unless there is a fault at the hpp or could there be an electrical problem causing it? ie. hp sensor

the low pressure pump feeds the high pressure pump which feeds the injectors.

it could be electrical but once again, the high pressure pump ran dry and most likely has damage internally.

what was the original failure and did you do electrical checks before taking everything apart.

Roy

I disconnected the hp sensor to test for c/rail pressure under cranking (can this jam open)and also one by one all other sensors but no h/p.in c/rail at any stage which led me to believe a hpp problem had arisen because of the lack of lubrication from fuel.

with the sensor disconnected, there will be no pressure.
anyway, i agree that the pump is no good.

Roy

Thanks for your evaluation. John

good luck

Roy