Field Service Bulletin
Bus System Manifold Retro-Fit

ENP-126
April 13, 2015

1. Introduction
Some bus systems use a two-piece manifold (located in the fuel management module) and may
require replacement due to worn O-ring seals. When the O-ring seals need to be replaced, Agility
Fuel Systems recommends removing the old manifold and replacing it with a new and improved
solid block manifold that eliminates the internal O-ring seal. Changing the manifold requires new
plumbing components, as shown in Figure 1.

2. Affected Units
NABI buses before 2010 with a multi-piece manifold as shown in Figure 2.

3. Parts Needed
A manifold retrofit kit is available for this procedure. Order the Agility Fuel Systems NABI Manifold
Retrofit Kit, part number 20103324. Here is a list of parts included in the kit.

Figure 1 A kit containing all needed parts for the conversion is available. Order part number
20103324.

ENP-126: NABI Bus Manifold and O-Ring Retro-Fit

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REF
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
--

PART
NUMBER
20100259
10200345
10300632
10200290
10200256
10240403
10200383
10200385
10200391
10200392
10200397
10200180
10200402
10300803
10300804
10300809
10300810
10300811
10500013
10500014
10500032
10500054
10500025
10500014
10300589

QTY

DESCRIPTION

2
1
1
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
5
1
1
2
1
1
1

MANIFOLD SPACER
HOLLOW HEX PLUG
TUBE END SCREW WITH NUT/FERRULE
SWAGELOK 1/4-IN. NUT
1/4-IN. FERRULE SET
FEMALE SAE 1/4 MALE NPT CONN
1/4-IN. HEX NIPPLE
FITTING, PLUG, HOLLOW HEX, 7/16-20 MALE SAE
1/4-IN. SS STREET ELBOW NPT
1/4-IN. NPT STREET TEE
1/4-IN. TUBE ADAPTER FEMALE
ELBOW, 3/8-IN. TUBE x 9/16-18 MALE SAE
3/8-IN. x 3/8-IN. TS REDUCER ELBOW
1/4-IN. TUBE FROM DEFUEL VALVE FILL BOX BNT106
TUBE MANIFOLD VENT LINE
1/2-IN. TUBE ASSEMBLY
1/4-IN. TUBE ASSEMBLY
1/4-IN. TUBE ASSEMBLY
O-RING, BN-90-OR-904
O-RING, BN-90-OR-908
O-RING, OPW-001121
O-RING, OPW-001127
O-RING, BN-90-OR-906
O-RING, BN-90-OR-908
MANIFOLD ASSY. IS0103032410

Figure 2, Left: The new and improved manifold is a one-piece component. Right: The old manifold
has a noticeable seam near the bottom as shown in lighter blue.

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DANGER - WARNING



System components must not be under pressure during servicing to prevent serious injury or
death.
This document is intended as a supplement to training in operation and maintenance of the CNG
fuel system. Attempting to operate or maintain the CNG fuel system without proper training is
dangerous.

4. Procedure – Depressurize System
NOTE: Most parts will be re-used. Save all removed components in a clean and safe
place until this procedure is completed.
1. Depressurize the system.
2. Start the engine and run at idle until the engine stalls.
3. Isolate or disconnect battery power.
4. Check all gauges to verify zero pressure.
5. Crack the bleed valve open or the fuel supply line to release the remaining pressure.

4.1 Disassembly

Figure 3 The manifold is located inside the
FMM compartment at the rear (aft) end of
the bus, on the curb side of the vehicle.

Figure 5. Remove the defuel receptacle.

ENP-126: NABI Bus Manifold and O-Ring Retro-Fit

Figure 4. Old manifold shown. Make sure
the system is depressurized before
performing any work on the system.

Figure 6. Remove the four manifold mounting
bolts.

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1.
2.
3.
4.
5.
6.
7.
8.

Disconnect the electrical connector going to the solenoid valve.
Disconnect defuel line and P-clips.
Remove the outlet tube and coalescing filter.
Remove the inlet tube to the coalescing filter and manifold.
Loosen the 90-degree elbow and coalescing filter to simplify procedure.
Remove the defuel receptacle, as shown in Figure 5.
Remove the 4 manifold mounting bolts and remove the manifold (Figure 6).
Place the old manifold in a bench vise to remove the following parts as shown in Figure 7.
a) Pressure transducers (2 each, as equipped)
b) Gauge
c) Elbow
d) Fill receptacle

Figure 7 Remove parts from the manifold.

Figure 8 Re-installing parts on the manifold

4.2 Reassembly
1.
2.
3.
4.
5.
6.

Place the new manifold in a bench vise to install the following components
1/4-in. fitting
3/8-in. tube stub 90-degree elbow, do NOT tighten
90-degree elbow, do NOT tighten
U-shaped tube, do NOT tighten – see Figure 9
Move the components on the manifold so everything fits inside the cabinet, and can be
accessed to connect the other plumbing items, then tighten all fittings
7. Remove fittings from the FP transducer, remove all traces of Poly-Temp tape, and clean
threads with alcohol
8. Apply new Poly-Temp tape
9. Install new tube stub fittings into the manifold
10. Clean and install elbow, do NOT tighten
11. Clean and install transducers and tighten all fittings
12. Clean and install elbow, do NOT tighten
13. Clean and install plugs (4)
14. Clean and install 90-degree elbow
15. Clean and install adapter
16. Clean and install dust cap
17. Clean and install defuel receptacle
18. Clean and install fitting*
*Only if two transducers
are present

ENP-126: NABI Bus Manifold and O-Ring Retro-Fit

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19. Clean and install Tee fitting
20. Clean and install FP transducer*
21. Clean and install gauge
22. Clean and install fill receptacle, remember to remove and replace the O-ring

4.3 Install Manifold Sub-Assembly
1.
2.
3.
4.

Loosely fit manifold in place and attach supply line, do NOT tighten
Attach 1/2-in. tube from manifold to coalescing filter, do NOT tighten
Mount the new manifold using the 4 manifold mounting bolts
Tighten the supply line

Figure 9 U-shaped tube loosely attached.

4.4 Final Assembly

Figure 10 All components mounted on the
manifold.

1. Move/adjust all fittings on the 1/2-in. manifold line to the coalescing filter tube and tighten all
fittings
2. Install all defuel vent lines, cut and deburr the lines as needed
3. Replace vent caps
4. Install defuel line P-clips
5. Attach the electrical connector to the solenoid valve

Figure 11 The new manifold installed. The fill
receptacle and gauge is installed next.

ENP-126: NABI Bus Manifold and O-Ring Retro-Fit

Figure 12 A view of the completed installation,
ready for leak testing.

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4.5 Testing
Ensure the 1/4-turn valve is in the CLOSED position
1. OPEN the manual hand valve
2. Turn battery power ON
3. Gradually open the 1/4-turn valve
4. Check all supply lines and fittings for leaks and fix as needed
5. Start and run the engine
6. Check for leaks again, and fix as needed
7. Open the remaining manual valves for normal operation.

5. Warranty Information
Standard repair time (SRT) is 4 hours, and is not covered under the standard warranty.
Contact Agility Fuel Systems Product Support at 949-267-7745 or [email protected] for more
information.
Warning Message Used in this Bulletin

DANGER - WARNING
Personal injury or death may occur if procedures are not followed.
Proprietary Statement
The information provided within this document is proprietary and confidential. All prior versions,
including updates and revisions forwarded separately, are proprietary. The information provided by
Agility Fuel Systems to its customers and clients is solely for the use of those customers and
clients. No portion of this manual may be reproduced or distributed without express written consent
of Agility Fuel Systems. Agility Fuel Systems reserves the right to utilize the intellectual property
contained within this publication as content for any other publication produced by Agility Fuel
Systems.
Trademark Notice
Agility Fuel Systems® is a registered trademark of Agility Fuel Systems. Drop-N-Go™ is a
trademark of Agility Fuel Systems. Trademarks of other manufacturers are the property of their
respective companies.
Agility Fuel Systems
1815 Carnegie Ave
Santa Ana, CA 92705 USA
Product Support
949-267-7745
[email protected]
www.agilityfs.com
Table 1 Revision History
Revision

Description

Author

Approved By

Date

--

Initial Release

W. Yoshida

D. Cate

4/13/15

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