This procedure will allow the low pressure fuel system to be monitored using pressure gauges.
- Place a towel or container under the fitting for the low pressure pump out to catch any draining fuel.
- Remove four 8mm plug fitting in each of the four lines: low pressure pump inlet (1), low pressure pump outlet (2), high pressure pump inlet (3), and high pressure pump outlet (4). Store fittings to be reinstalled when testing is complete.
- Insert four quick disconnect fittings into each of the four fuel line test ports.
- Torque each fitting to 8 Nm (6 ft/lb).
- Install priming port gauge J-48876.
- Prime the fuel system. Refer to “2.5 Engine Will Only Start Using An External Priming Source” .
- Start the engine; refer to “16.5.1 Fuel System Pressures” and compare the pressures to the tables found there.
- Remove test equipment
Fuel System Pressures
Normal and abnormal fuel system pressure are listed in the following tables.
| Normal System Pressures | ||||
| | Cold Engine 600 RPM | Cold Engine 1800 RPM | Warm Engine 600 RPM | Warm Engine 1800 RPM |
| LPP Inlet (in Hg | -8 to-9 | -14 | -7.5 | -13.5 |
| LPP Outlet (PSI) | 78-80 | 104 | 73-74 | 97 |
| HPP Inlet (PSI) | 74-76 | 87 | 70-71 | 83 |
| HPP Outlet (PSI) | 2.5 | 4.5 | 2-2.5 | 4 |
| Priming Port (PSI) | 78-80 | 101 | 72-73 | 94-95 |
Table 1. Normal Fuel System Pressures
| Abnormal Fuel System Pressures | ||||
| | Coalescer (at or past its useful life) | Final Filter (at or past its useful life) | ||
| Warm Engine 600 RPM | Warm Engine 1800 RPM | Warm Engine 600 RPM | Warm Engine 1800 RPM | |
| LPP Inlet (in Hg) | -8.5 | -13.5 | -5.5 | -6 |
| LPP Outlet (PSI) | 82 | 122 | 160+ | 160+ |
| HPP Inlet (PSI) | 72 | 90 | 65 | 66 |
| HPP Outlet (PSI) | 3 | 4 | 1-2 | 2 |
| Priming Port (PSI) | 75 | 105 | 160+ | 160+ |
| | Restricted Fuel Feed Line to Module | Restricted Fuel Return Line From Module | ||
| Warm Engine
600 RPM |
Warm Engine
1000 RPM |
Warm Engine
600 RPM |
Warm Engine
1000 RPM |
|
| LPP Inlet (in Hg) | -12 | -14.5 | -4.5 | -6.5 |
| LPP Outlet (PSI) | 69 | 80 | 75 | 91 |
| HPP Inlet (PSI) | 67 | 75 | 72 | 84 |
| HPP Outlet (PSI) | 1-2 | 1-2 | 4.5 | 5.5 |
| Priming Port (PSI) | 70 | 80 | 75 | 90 |
| | Air in System (connector at line to MCM) | | ||
| Warm Engine
600 RPM |
| | | |
| LPP Inlet (in Hg) | -1 to -5 (oscillating) | — | — | — |
| LPP Outlet (PSI) | 14 | — | — | — |
| HPP Inlet (PSI) | 14 | — | — | — |
| HPP Outlet (PSI) | 1-2 | — | — | — |
| Priming Port (PSI) | 14 | — | — | — |
Table 2. Abnormal System Pressures
