First off its not a sensor, VCV is the Volume Control Valve. The VCV is located on the high-pressure side of the fuel pump. The valve regulates the fuel supply (and hence the quantity of fuel) coming from the transfer pump (low pressure side working on a vacuum of -20 to -30 Kpa) to the high-pressure side of the fuel pump, it is controlled directly from the EMS opening and closing depending on the fuel pressure of the rail, engine power demands etc. This makes it possible to match the delivery of the high-pressure fuel pump to the requirements of the engine from the low-pressure side, ie enough fuel is available on the high pressure side of the pump to allow maximum rail pressure and engine fuelling requirements to maintain a steady delivery of power from the engine. HTH

A previous post

Lorryman100 wrote:

If none is found then I would move onto the Fuel pump, but first let me explain how it works.
The fuel pump contains and controls both the low pressure and high pressure systems. The low pressure side of the pump is responsible for getting the fuel from/and return to the tank and into the pump to be utilized in the high pressure system. It does this by using an eccentric cam to draw fuel along the fuel pipes and into the pump. There is an admissions valve to control the volume (also ensures that sufficient lubrication and cooling are always provided for the high-pressure pump components) and also a temp sensor to determine the fuel density by its temperature, if this sensor is faulty or unplugged the defender will enter limp mode. Fuel is then passed into the high pressure side by way of the Volume Control Valve which is controlled by the EMS. It basically governs the flow of fuel from the low to the high pressure side to maintain the fuel accumulator rail at a set pressure. It operates by means of the EMS using the information from the fuel rail pressure sensor to maintain the pressure at the fuel rail, about 1600BAR.
A total of 2 high-pressure chambers, each with a pump plunger, are used for high-pressure generation. The drive for the pump plungers is through an eccentric cam, which is in turn driven by the drive shaft. The high-pressure pump permanently generates the high system pressure for the fuel rail. The rotary movement of the drive shaft is converted to a reciprocating movement by the eccentric cam. The eccentric cam ring then transfers the reciprocating movement to the pump plungers. The pump plungers are offset by 180 degrees. This means that during a reciprocating movement, pump plunger 1 performs exactly the opposite movement to pump plunger 2. When the eccentric cam produces an upward stroke, pump plunger 1 moves in the direction of Top Dead Center (TDC), thus compressing the fuel and delivering it to the fuel rail via the outlet valve. The inlet valve is pressed into its seat by the delivery pressure. Pump plunger 2 is moved by the tension spring force in the direction of Bottom Dead Center (BDC). Due to the high pressure in the fuel rail, the outlet valve is pressed into its seat. The pump internal pressure opens the inlet valve and fuel flows into the high-pressure chamber. When the eccentric cam produces a downward stroke, the process is reversed.
So if we check the pressure at the rail, we can see if the high pressure pump is causing the issue. If not then the low pressure system must also be not at fault as it supplies the high pressure system. So next on the list is the injectors themselves, not much here you can check without removing them, and if you do you will need new copper washers first to replace the old ones. The faults here range from broken actuator springs to cracked pressure casings. Though if an injector was failing/failed then the solenoid on top would not operate as intended and would throw up a dtc in the EMS?

Caterham wrote:

so map sensor and vcv replaced. injector learn and pump all done.

no obvious improvements, certainly my intermittent 'knocking / injector noise' hasn't gone completely.


gave the MAF sensor and electrical connectors and wiring a good clean and wiggle last night.....

this moring the engine seemed very lively....almost like it was running away with itself (compared to what I'm used to) so it looks like next move is a MAF sensor.........

£150 from Ford

seems Ford are cheaper for some things and more for others