worcester heatslave oil pump running pressure

[am609]

I have a heatslave 15/19 with a B11 burner using gas oil.The boiler has started locking out,I have connected a press gauge at the pressure port on the nozzle block and the press is initially 105psi when burner fires but decreases to aroud 80psi then lockout occurs when press falls below 75psi.
Any ideas,is this a characteristic of a failing pump?
Before anyone asks there is plenty oil in tank and filter has been cleaned at the boiler.

 

[wilhelm]

what i would do is adjust up to 100psi. first, if it will.
but yes this pump sounds as if it is nadgered.
check drive dog 'tho. might be bit rounded giving your syptoms also.

 

[oilman]

Gas oil pressure for the 15/19 is 155psi using a 0.5/80S nozzle. Lower pressure will give lower output, and poorer combustion.