My D1 reads 30 PSI at idle on the fuel rail valve port. This drops to 28 momentraily when the engine is revved, then returns to 30. It stays at 30 when engine is off, although I have not left it overnight to be sure it does not leak down slowly. Cranking in mornings is normal, no extended cranking time needed. When I just turn on the switch to run, but don't crank, the PSI goes to 34 or so then drops back to 30. Based on the 2.54 Kgf/cm2 given in the RAVE as normal, that would convert to roughly 36 PSI. So would this be an early indicator of a failing fuel pump, or just a good indication of a fuel filter that needs to be changed? Or a fuel pressure regulator that needs replacement? Do Disco fuel pumps slowly degrade, or is it usually go/no go?

 

1. change the fuel filter anyway, less stress on the pump.
2. imo the pressure is a little low but not bad.
3. with that mileage, you're likely to need a pump( if it hasnt been done already) sometime.
4. slow degrade to the point of needing to prime it 2-3 times to get going in the morning is the normal pattern, but like anything else....it can just quit. Mine ran for months with the extra prime method till I got around to changing it. when I got it out there was metal fillings and schrapnel in the bottom of the canister...

 

Update - changed fuel filter, bad news is that it was a Purolator, so it was not original neglect, PO had changed it in the past (amazing!). PSI went to maybe 31, still drops to 28 when engine runs at 1500 rpm and above. Went by the salvage yard (my second home) and got a fuel pump. Problem was that salvage yard forklift had lifted the Disco and squashed the tank. The plate in the rear cargo area was bowed up, the pump assembly was pushed out of the seal, plastic parts deformed. Got the internal pump anyway.

Do we have a fuel pump substitution write up lurking somewhere? Kinda like the Chevy van fan clutch...

 

Read through here, there is a part number for another fuel pump.

Discovery I Fuel Pump Removal / Fix - Land Rover Forums - Land Rover Enthusiast Forum

 

At your mileage, if you want to maintain some power replace your warn pump using an AirTex from Advanced Auto parts, they offer 2, 1 actually makes an extra 16 pounds pressure for the little extra punch when you need it for those old injectors.

 

It could also indicate a weak pressure regulator, but more than likely a weak pump from too few filter changes.