Originally Posted by
BradC
The returned fuel only goes to the filter in the EU3 D3s (<2007 I suppose). The early filter was designed to return warmed fuel through the filter to try and reduce gelling in cold weather. This has a thermostatic bypass to prevent the filter from cooking and once warm the flow is diverted to the tank. That configuration was removed with the move to EU4 . EU4 D3s and all D4s return straight to the tank.
The Volume control valve is a component of the high pressure fuel pump. The fuel enters the pump via a vane feed pump, through the VCV which recirculates fuel when under light load. It then passes to the high pressure pump and the spill from the PCV on the pump output goes back to the return line along with a small low pressure flow that passes through the pump housing to cool and lubricate.
I don't have first hand experience with the early EU3 discos, so there may well be something there that's not in the manual, parts list or system descriptions. But there is certainly no significant back pressure in the return line on my EU4 D3. The 2.7 D4's use the same fuel configuration.
Soooo, what is the purpose of this restrictor?
I'll try to confirm year/s of the two cars involved.
Before: Ser 2a LWB, Ser 3 S/W, 1979 RR 2 door, 1981 LR Stage 1 V8 (new), 1985 LR 110 V8 County (new), 2009 RRS TDV8
Now: MY13 D4 TDV6. "E" rear diff. Cambo's magic Engine & Auto Tune.
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