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| Position pressure gauge device, e.g. -VAS 5187-, as shown in the figure. |
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| Start engine and run in idle. |
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| Observe pressure displayed on pressure gauge. |
| Specified value: min. 0.35 MPa (3.5 bar) |
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| Engine speed must increase to 4000 rpm. |
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| Note the pressure shown on the manometer. |
| Specified value: min. 0.75 MPa (7.5 bar). |
If the nominal value of min. 0.75 MPa (7.5 bar) is not reached: |
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| Unclamp return-flow line between tandem pump and fuel filter with hose clamp -MP7-602 (3094)-. |
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| Start engine and engine speed must increase to 4000 rpm. |
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| Note the pressure shown on the manometer. |
| Specified value: min. 0.75 MPa (7.5 bar). |
If the specified value is reached: |
Pressure loss at the unit injectors. |
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| Replace O-rings for unit injectors. |
If the specified value is still not reached: |
Note After removing the pressure gauge tighten screw plug to 25 Nm. Always replace the gasket ring. |
Check tightness (internally) |
Note After re-installing a used tandem pump e.g. after changing or repairing a cylinder head and/or after changing a hopper motor the tandem pump must absolutely be checked for internal tightness between fuel and oil side. In case of leakage the fuel penetrates into the engine oil, which can cause severe engine damage. |
Special tools and workshop equipment required |
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| Disconnect the fuel feed hose (white marking) and the fuel return hose (blue marking) from the tandem pump. |
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| Close fuel return-flow connection at tandem pump with a dummy plug. Secure the dummy plug with a spring strap clamp. |
Prepare tester -V.A.G 1687- as follows: |
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