Quote:
Originally Posted by HarryM1BYT
I don't think the ITP pump type would generate anything like 52PSI, so why a pressure regulator there and are you suggesting that the regulator is actually in the tank? If it is indeed there, between ITP and UBP - why there, surely it would have been more sensible to have a regulator after the UBP?
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Harry there is another pressure relief valve fitted after the UBP which will bypass fuel back to the inlet side of the UBP in the event of any over pressure between the UBP and HP pump.
Interestingly the ITP has its own pressure relief valve, a ball and spring valve built into its casing. So It is a mystery that the pressure relief valve in the tank is set at 52 psi. I can only think it may be there to vent any excess pressure if there is a fault in the HP pump and the return side.
That doesn't make sense looking at the drawing, but as I mentioned earlier when the fuel is cold and the thermostatic valve is closed it looks like the returning fuel circulates straight back to the UBP not to the tank with the ITP topping up what is lost to the HP pump. So that is effectively a closed circuit with only a restrictor going back to the tank, and it would need a pressure relief valve fitted.
Good idea to carry a spare UBP - I keep my old good one in the boot just in case. No need to worry about the ITP - if it fails just keep the tank over a quarter full and it will run fine.
Mike