Cummins/Onan NHP / NHPV Engine

Tools: Allen wrench, Flat thickness gauge

1. Remove spark plugs and rotate flywheel TC mark to 25 degrees BTC, then 90 degrees clockwise.
2. Remove breaker box cover and unplug coil wire at coil (+) terminal.
3. Remove condenser (screw A) and detach condenser and coil leads (screw B).
4. Remove two Allen screws (C) and lift breaker assembly from engine.
5. Replace condenser and point assembly and reinstall in reverse order.
6. Adjust point gap at .019 inch (0.48 mm) using a clean flat thickness gauge.
7. Replace breaker box cover and spark plugs.

⚠ Avoid high loads before proper adjustments are made.

1. Run new engine at least ten hours at normal service load.
2. Run engine at maximum throttle at normal rpm for ten minutes.
3. Set main power mixture as lean as possible without noticeable power loss.
4. If frost remains on regulator over five minutes, check for leaks and vaporizer coil wrap.
5. Recheck head bolt torque and valve lash after carburetor is adjusted.

⚠ Run engine about 15 minutes to reach normal operating temperature before adjusting.

Tools: Tachometer

1. Adjust the carburetor main jet for best fuel mixture at full load.
2. Adjust the carburetor idle needle with no load connected.
3. Adjust the length of the governor linkage.
4. Check governor linkage and throttle shaft for binding or excessive looseness.
5. Adjust governor spring tension for nominal engine speed at no load.
6. Check rpm drop between no load and full load; adjust sensitivity as needed.
7. Recheck the speed adjustment.
8. Set the carburetor throttle stop screw.

1. Run engine at idle speed (1200 rpm) for ten minutes.
2. Adjust idle screw for maximum speed.
3. Set idle stop screw speed at 1350 rpm.
4. Turn idle screw out until engine speed slows to 1200 rpm.

⚠ Do not permit any flame, cigarette, or other igniter near the fuel system.

1. Set main power mixture to position shown in Figure 19.
2. Turn idle screw in fully clockwise.
3. Turn idle screw out 2-1/2 turns counterclockwise.
4. Connect or turn on fuel supply to regulator.
5. Check (smell) for propane leaks.
6. Start engine; it should start within 20 seconds if fuel is available.

⚠ Adjust valve clearance only when engine is at ambient temperature.

Tools: Feeler gauge, Standard automotive type wrench

1. Remove parts needed to gain access to valve tappets.
2. Remove spark plugs to make turning the engine easier.
3. Turn engine by hand until left intake valve opens and closes; align TC mark.
4. Check clearance with gauge between valve stem and tappet.
5. Turn adjusting screw as needed; screw is self locking.
6. Turn engine one revolution and adjust right hand cylinder the same way.
7. Replace all parts removed and tighten securely; torque manifold bolts.

Tools: Continuity test lamp

1. Connect a continuity test lamp across the ignition breaker points.
2. Touch one prod to breaker box coil terminal, other to a good engine ground.
3. Turn crankshaft counterclockwise until points close.
4. Slowly turn crankshaft clockwise with rotation.
5. Lamp should go out just as the points break (25 degrees BTC).

Tools: Timing light

1. Connect a timing light according to its manufacturer's instructions.
2. Either spark plug can be used as they fire simultaneously.
3. Start engine and check timing at idle speed.
4. Pointer on flywheel should line up with 25 degree mark on cover.
5. If marks do not line up, readjust point gap (open to advance, close to retard).
6. Recheck timing and breaker point gap after adjustment.

⚠ Do not remove heads when they are hot. Warpage may occur.

Tools: 9/16-inch socket wrench, Torque wrench

1. Use a 9/16-inch socket wrench to remove cylinder head bolts; lift heads off.
2. After removing heads, clean out all carbon deposits carefully.
3. Use new head gaskets and clean heads and cylinder block thoroughly.
4. Place heads in position and tighten bolts in sequence to 5 ft-lb, then 10 ft-lb, etc.
5. Torque all bolts to 15 ft-lb (20 N.m).
6. Recheck torque before engine has run a total of 50 hours.

⚠ Discharged batteries are subject to severe damage if exposed to freezing temperatures.

1. Run engine until thoroughly warmed up.
2. Turn off fuel supply and run until engine stops from lack of fuel.
3. Drain oil from oil base while still warm; attach warning tag to refill.
4. Remove each spark plug; pour one ounce of rust inhibitor or SAE #50 oil into cylinder.
5. Crank engine over a few times; reinstall each spark plug.
6. Service air cleaner per maintenance schedule.
7. Lubricate governor linkage; wrap with clean cloth.
8. Plug exhaust outlet and cover unit; disconnect battery and follow battery storage procedure.

⚠ Do not smoke while servicing batteries. Explosive gases are emitted.

Tools: Hydrometer

1. Check service identification tags to properly service the engine.
2. Uncover and remove all storage seals; remove dust, dirt, or foreign matter.
3. Check fuel supply tanks, lubricating oil, fuel line, wiring and exhaust connections.
4. Service air cleaner per maintenance schedule.
5. Verify oil viscosity is correct for existing ambient temperature.
6. Clean and check battery; measure specific gravity (1.260 at 25 C) and verify level.
7. Check engine for fuel or oil leaks; correct as required.
8. Install fully charged batteries; start engine and check for leaks, voltage output and cooling.

1. Crankcase turned on left side.
2. Unscrew oil pump assembly from intake cup.
3. Check oil pump thoroughly for worn parts.
4. Oil the pump to prime it before reinstalling.
5. Install a new pump assembly if required.
6. To reassemble, reverse the procedure.