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Old 02-11-2009, 07:40 PM   #2
Steve Escos
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P0251 (Fuel metering valve (IMV) control error)
Symptoms:

Extremely poor engine performance - glow plug warning lamp flashes.

Engine cuts out - glow plug warning lamp flashes.

*Engine will not start.

Cause:

The fuel rail pressure demanded by the system cannot be achieved without the IMV opening beyond the tolerance specified for that pressure.

NOTE: The fault descriptions listed below should be worked through in order.

1. Restriction in the low-pressure fuel system, which could be caused by a blockage of a fuel line or the fuel filter, or a damaged fuel line.

2. Air in the low-pressure system: Leaking fuel lines or connections can cause air in fuel.



3. Faulty fuel injection pump, transfer pump part, or pressure control valve. Fuel injection pump internal transfer pressure needs to be at least 6 bar to achieve high pressure chamber filling (to generate the required fuel rail pressure). Check the following (if the engine does not start):

Remote feed the fuel injection pump with a filtered, proprietary fuel supply. If the engine will start when the fuel supply is pressurized or held above the fuel injection pump intake (gravity fed), but will not start when the fuel supply is not pressurized or held below the fuel injection pump intake then it is likely that there is a fault with the internal transfer pump (i.e. not able to draw fuel).
4. Faulty fuel injection pump - high-pressure part or inlet metering valve (IMV):



Check the fuel pressure (with the ignition ON, engine OFF) (it should fluctuate between 4 and 10 bar maximum). If a default fuel pressure of 2000 bar is displayed then there is an electrical fault on the fuel pressure sensor (connector, wiring etc.).
Check the fuel pressure at the moment the engine starts (target value = 300 bar 50 bar).
Check the fuel pressure at idling (target value = 250 bar 40 bar).
5. Injectors:


6. Swarf in the system:

it is possible there may be swarf in the system, without the fuel injection pump being defective. A sample of fuel should be collected from the fuel injection pump return line. swarf ).
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