Field Service Bulletin
Mack UPS LNG Regulator Orientation
ENP-127
February 17, 2014

1. Introduction
The initial production run of UPS Mack LNG trucks were built with the pressure regulator in an
inverted position (adjustment handle on top). A production change was implemented after
production of about 120 units to facilitate drainage of water or other contaminants that may have
entered the regulator through the drain holes. This campaign is authorized to achieve fleet
consistency for UPS.

2. Affected Units
This procedure applies to approximately 120 Mack - UPS LNG Agility Fuel Systems vehicles from
the first production run. Current production units are configured correctly and do not require
service.
Only one new part is needed for this retro-fit: The Solenoid/Regulator Protective Cover, part
number 23804103.
There is no need to replace the regulator - the same regulator may be re-installed in the corrected
position.

3. Corrective Action
Remove and replace the Solenoid/Regulator Cover and replace it with a new one, part number
23804103. Remove the existing regulator from the heat exchanger mounting plate, drill two new
holes for the regulator mounting bracket, turn the regulator 180 degrees and re-assemble the subsystem, see Figure 1. The ECU mounts to the new protective cover.

4. Procedure

Figure 1. The Heat Exchanger Subassembly. The vertical supports are not shown to improve clarity.
The regulator must be removed and re-mounted 180 degrees from its present position. The change
moves the location of the pressure gauge, so a new protective cover is required.

Mack UPS LNG Regulator Orientation

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Figure 2. Removal procedure sequence. Two new holes must be drilled into the existing mounting
plate to accommodate the re-positioned regulator.

WARNING: System components must not be under pressure during servicing to
prevent serious injury.

4.1 Depressurize the System
1. Turn the ignition off and ground the chassis.
2. CLOSE the red handle shutoff valve.
3. Locate the engine low pressure filter petcock, and slowly “crack open” the handle
counter-clockwise to vent LNG to the atmosphere.
4. Turn the ignition switch to ON, but do not start the engine. This activates the solenoid
valve and vents the tank.
5. The system is now depressurized and work may be performed. Note, the tank is still
pressurized.

4.2 Perform the Retro-Fit
Refer to Figure 2.
1. Remove the existing protective cover. It will not be re-used (item 1).
2. Disconnect the 1/2-in. male connector at the fuel port heat exchanger output (2).
3. Remove the two bolts securing the regulator bracket (3) to the heat exchanger
mounting plate.
4. Remove the bolts securing the low temperature sensor (4) to the mounting plate.
5. Un-plug the solenoid valve wire connector (5) from the ECU.
6. The regulator, mounting bracket, solenoid valve and gauge should now be removed
as an assembly.

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7. Remove the regulator from its bracket. Use the bracket as a template to drill two
new holes in the mounting plate, approximately 3-5/16 above the upper-most pair of
holes. Before drilling, check for any interference issues.
8. The gauge must be be removed from the regulator body, and re-located to the
opposite side, as shown in Figure 3.

B

A

Figure 3. “A” shows the old regulator orientation and a plug. The new location flips the regulator over,
and the gauge and plug must be mounted on the opposite sides of the regulator body.

9. Re-assemble the removed components and mount them onto the mounting plate. It
should look like the picture below.

Figure 4. The re-installed regulator and related components mounted on the original mounting plate.

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4.3 Repressurize the System
1.
2.
3.
4.

Close the engine low pressure filter petcock.
Leave the red handle shutoff valve OPEN for normal operation.
Test for leaks and correct as needed.
Return the vehicle to normal operation.

Standard repair and warranty labor period per the Agility Fuel Systems Warranty Manual applies
for this procedure. Time to complete this procedure is 1.5 hours. This procedure is limited to the
initial 120 Mack – UPS vehicles as mentioned in the introduction section.
If you have any questions, contact Agility Fuel Systems Product Support at +1-949-267-7745 or
[email protected].
Agility Fuel Systems
Product Support
1815 Carnegie Ave
Santa Ana, CA 92705 USA
+1-949-267-7745
[email protected]
www.agilityfs.com

Mack UPS LNG Regulator Orientation

Revision History

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WY

2/17/14

Initial release

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DESCRIPTION

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