Cummins/Onan — Tailpipe Installation
Installation · exhaust tailpipe
From a Cummins/Onan service manual covering: 5.5 HGJAA, 5.5 HGJAB, 6.5 HGJAA, 6.5 HGJAB, 7.0 HGJAA, 7.0 HGJAB. Check it applies to your exact model before use.
Applies to: Cummins/Onan HGJAA, Cummins/Onan HGJAB
Before you start
- Do not use flexible pipe for tailpipe.
- EXHAUST GAS IS DEADLY!
- This product incorporates a catalyst exhaust system which leads to higher exhaust gas temperatures.
Procedure
- Use 18-gauge 1-3/8 inch I.D. aluminized steel tubing or material of equivalent heat and corrosion resistance.
- Support a tailpipe longer than 457 mm (1-1/2 ft) near its end and at intervals of 900 mm (3 ft) or less.
- Use automotive-type tailpipe hangers. Do not attach hangers to combustible material such as wood.
- Use U-bolt muffler clamps to connect sections of tailpipe. Overlapping pipe should be slotted.
- Do not route the tailpipe closer than 114.3 mm (4.5 in) to fuel lines or fuel tanks.
- Do not route the tailpipe closer than 76 mm (3 in) to combustible material unless insulated or shielded.
- Do not route the exhaust tailpipe underneath the oil drain.
- Do not route the exhaust tailpipe under the air inlet or in a way that restricts the air inlet/outlet.
- Do not route it into the approach/departure angles or below the axle clearance line.
- Do not interconnect generator set and vehicle engine exhaust systems.
- Do not terminate the tailpipe underneath the vehicle; extend it a minimum of 25 mm (1 in) beyond the perimeter.
- Do not terminate the tailpipe closer than 153 mm (6 in) to any opening into the vehicle interior.
- Make sure the tailpipe system will not cause excessive back pressure; back pressure cannot exceed 6 to 8 inches WC.
Tools required
- U-bolt muffler clamps Amazon
- Automotive-type tailpipe hangers Amazon
- u-tube manometer Amazon
- barb fitting Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Exhaust back pressure: 6 to 8 inches of water column (1/3 psi)
- Tailpipe: 18-gauge 1-3/8 inch I.D. aluminized steel
- Clearance to fuel lines/tanks: 114.3 mm (4.5 in) min
- Clearance to combustibles: 76 mm (3 in) min
Full service-parts list: Cummins/Onan HGJAA →, Cummins/Onan HGJAB →
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.