The UK quattro Network

Audi ur-quattro 10V WR, WX and GV Engines
Checking the Cold Start Valve

The 1980-1987 WR ur-quattro's cold start valve (N17) is powered by the starter solenoid and can only spray when the starter is turning. A thermotime switch (brown, back of cylinder head) contains a small heater and breaks the chassis ground from the cold start valve after a period of time dependent on the temperature of the coolant at the back of the cylinder head. Both the thermotime switch heater circuit and the cold start valve circuit are grounded to the chassis through the sender.

• Detach the cold start valve and place it in a measuring glass - the fuel line remains attached
• Replace the cold start valve connector
• Operate the starter. The cold start valve must spray in a uniform bell-shaped pattern

• The duration of the first spray must lie within tolerance according to the ambient temperature or, more accurately, the temperature seen by the thermotime switch in the back of the cylinder head. The results of subsequent tests may be variable - the thermotime switch contains a mechanism to prevent the cold start valve being operated too frequently; this is to prevent fuel accumulating in the cylinders causing a hydrolock that might - worst case - lift the head from the block. Thus it is best to leave at least one and sometimes up to three minutes between consecutive attempts to measure the initial spray time.
  
  An Excel spreadsheet is available here - the initial spray time should lie between the Min (blue) and Max (red) values. At normal European ambient temperatures, time measurement may be tricky and normal experimentation procedures (e.g., independent time recording) should be considered. If extensive measurements are made, the oil level should be checked after the first subsequent long run.
  
  On the WR engine and its variants, the duration of the spray is controlled by the thermotime switch (part number 043 906 163A - rear of cylinder head) and ths is the first component to be checked in the event of the above tests failing.

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