Troubleshootings for Delphi Common Rail IMV Valve
Posted: 2015-03-12 22:26:18 Hits: 10622
IMV is the abbreviation of fuel ratio control valve. IMV valve controls the proportion between fuel mount and oil return amount entering into high pressure chamber. This ratio is influenced by current magnitude through IMV. When current is zero, IMV is fully on. The aperture of IMV decreases with the increasing of current, reducing to a certain fixed value.
Disconnecting IMV valve, the current is zero and IMV valve is fully on. Then the oil input reaches the maximum. Under the condition that revolving speed of fuel pump does not vary, the pressure reaches to the maximum, causing the rail pressure is always 200.00MPa.
When Delphi common rail fuel system cannot start successfully, decoder show fault codes as follows:
P0087: Starter rotating speed is too low, failed to establish the rail pressure.
P1253: IMV valve controller error (Pressure is too high, the negative fault).
P1254:IMV valve controller error (Pressure is too high, the positive fault).
P1257：IMV valve controller adjust error (IMV valve adjustment current is too high).
Two malfunctions are shown on Delphi common rail fuel system: one is that the rail pressure cannot be established; the other one is that IMV valve corrects wrongly.
The phenomenon is that it almost cannot start. Even the engine can start, trouble light also shines. Generally, high pressure pump has poor performance.
A lot of people change the parts, causing the maintenance cost is too high. This paper aims at telling the reasons causing malfunctions to people, so that can judge accurately and eliminate malfunctions. The analysis is as following:
IMV valve controller adjusts wrongly (adjustment current of IMV valve is too high), the stronger current is, the smaller aperture IMV valve is , supplying less oil to oil rail, vice versa. If IMV valve adjusting current is too high, that is the actual electric current is higher than designed current, or the actual aperture is smaller than design. So, the actual amount of fuel for oil rail is smaller than the design. But in the actual repairing, when nozzle leakage is too big, in order to ensure the necessary rail pressure, IMV valve’s aperture is bigger than the design and the electric current is smaller than design, to meet the requirement. This fault code should be reported: IMV valve adjusting flow is too low, not too high.
TMV valve of Delphi system often appears such failure. Generally cold car cannot be driven by starting engine. Whether it is new battery or new motor, just pushing the car can start. Therefore, such failure phenomenon, it is generally caused by IMV valve.
