TAG 2058389 - Caterpillar

Table 2
Specifications for Pressure Loss
Direct Injection Fuel Systems    
Nozzle pressure must not drop below a gauge reading of
3450 kPa (500 psi) during a 5 second time interval.    
Nozzle pressure must drop below a gauge reading of
1380 kPa (200 psi) after an additional 25 second time interval. (1)    
( 1 ) A gauge reading of 0 kPa (0 psi) is acceptable after the first 5 second time interval has elapsed.
Illustration 3 g00923167
If the fuel nozzle is not within specifications, stop the test and do not use the fuel nozzle.Valve Opening Pressure Test
Slowly increase the pressure until fluid begins to flow from the tip of the fuel nozzle. Record this pressure as the VOP of the fuel nozzle.
Compare the test results to the specifications for the type of fuel nozzle that is being tested. Refer to Table 3, or Table 4.For precombustion chamber fuel systems, use these specifications:
Table 3
Specifications for Valve Opening Pressure
Precombustion Chamber Fuel Systems    
2760 to 5170 kPa (400 to 750 psi)    
Illustration 4 g00934108
If the VOP is not within specifications, stop the test and do not use the fuel nozzle.For direct injection fuel systems, use these specifications:
Table 4
Specifications for Valve Opening Pressure
Direct Injection Fuel Systems    
16500 to 21400 kPa (2400 to 3100 psi)    
Illustration 5 g00923174
If the VOP is not within specifications, stop the test and do not use the fuel nozzle.Tip Leakage Test (Direct Injection Fuel Systems)
Note: Fuel nozzles for precombustion chamber fuel systems can not be tested for tip leakage accurately. Do not perform this test on fuel nozzles for a precombustion