DD 15 – Section 5.3 Monitoring Low Pressure Fuel System Pressures

Section 5.3
Monitoring Low Pressure Fuel System Pressures

Determine if you have Version 4 or Version 5 fuel system to use the following procedures.‪

Section 5.3.1
Low Pressure (Version 4 Fuel System)

This procedure will allow the low pressure fuel system to be monitored by using pressure gauges.‪

1. Drain fuel system. Refer to "6.1 Draining Fuel System Prior to Repairs" .
   
2. Remove the low pressure pump return line (2) and install the test line (6) from kit J-48706.
3. Remove the high pressure pump return line (4) and install the test line (5) from kit J-48706.
4. Remove the banjo bolt from the low pressure pump inlet (1) and install the banjo bolt from kit J-48706.
5. Remove the banjo bolt from the high pressure pump inlet (3) and install the banjo bolt from kit J-48706.
6. Connect the pressure lines to the appropriate connector.
7. Install priming port gauge J-48876.
8. Prime the fuel system.
9. Start the engine; refer to "5.3.3 Fuel System Pressures" and compare the pressures to the tables found there.
10. Remove test equipment.

Section 5.3.2
Low Pressure (Version 5 Fuel System)

This procedure will allow the low pressure fuel system to be monitored using pressure gauges.‪

1. Place a towel or container under the fitting for the low pressure pump out to catch any draining fuel.
   
2. 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.
3. Insert four quick disconnect fittings into each of the four fuel line test ports.
4. Torque each fitting to 8 Nm (6 ft/lb).
5. Install priming port gauge J-48876.
6. Prime the fuel system. Refer to "4.1 Engine Will Only Start Using An External Priming Source" .
7. Start the engine; refer to "5.3.3 Fuel System Pressures" and compare the pressures to the tables found there.
8. Remove test equipment

Section 5.3.3
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

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	—‪	—‪	—‪