Cummins/Onan 6CT 8.3 Generator Set

Tools: Screwdriver, Tachometer, 13, 19 and 10 mm wrenches

1. Industrial: loosen locknut and back out the bumper spring screw.
2. Speed should drop 20-30 rpm as the screw is backed out.
3. Loosen locknut; set idle screw 20-30 rpm less than desired speed.
4. Turn idle screw counterclockwise to decrease rpm; clockwise to increase.
5. Turn bumper spring screw in until desired idle speed is obtained.
6. Tighten the locknut.
7. Automotive: loosen locknut and turn screw counterclockwise to raise rpm, clockwise to decrease.

⚠ Be sure to disengage the engine timing pin after locating TDC

Tools: Screwdriver, 13, 14, 15 and 18 mm wrenches, Feeler gauge, Barring gear Part No. 3904682

1. Remove air crossover tube, support clamps and crankcase vent tube.
2. Remove the valve cover.
3. Locate Top Dead Center for cylinder number 1 using barring gear and timing pin.
4. Check/set valves with engine cold, below 60C [140F].
5. Adjust the valves indicated for STEP A (intake then exhaust).
6. Tighten locknut to 24 Nm [18 ft-lb] and re-check valve lash.
7. Rotate crankshaft 360 degrees; be sure timing pin is disengaged.
8. Set the valves indicated for STEP B; tighten locknuts to 24 Nm [18 ft-lb].

⚠ Wait until temperature is below 50C [120F] before removing the coolant system pressure cap

⚠ Do not install the radiator cap during flushing

Tools: Drain pan capacity 20 litres [5 U.S. gallons]

1. Wait until temperature is below 50C [120F] before removing pressure cap.
2. Open drain valve on radiator and oil cooler; drain the system.
3. Check for damaged hoses and loose clamps; replace as required.
4. Fill with sodium carbonate and water mixture; open vent petcocks.
5. Operate engine 5 minutes above 80C [180F]; shut off and drain.
6. Fill with clean water; operate 5 minutes; drain again.
7. Fill with 50 percent water and 50 percent ethylene-glycol antifreeze.
8. Install pressure cap; operate to 80C [180F] and check for leaks.

Tools: Cummins belt tension gauge ST-1293

1. Measure the belt deflection at the longest span of the belt.
2. Maximum deflection is 9.5 to 12.7 mm [3/8 to 1/2 inch].
3. Alternatively use the Cummins belt tension gauge ST-1293.
4. The required gauge value is 80 to 110 lbs.

⚠ The pressure of the fuel in the line is sufficient to penetrate the skin and cause serious bodily harm

Tools: 75-80 mm and 90-95 mm filter wrenches, 8mm wrench, 17mm wrench

1. Clean the area around the fuel filter head.
2. Remove the filters and clean the gasket surface of the filter head.
3. Replace the o-ring.
4. Fill the new filter(s) with clean fuel and lubricate the o-ring seal.
5. Install the filter as specified by the filter manufacturer.
6. Vent low pressure lines: open bleed screw and operate lift pump plunger.
7. Tighten the bleed screw when fuel flowing is free of air.
8. Vent high pressure lines one at a time at the injectors.

⚠ Hot oil can cause personal injury; drain only when oil is hot

Tools: 17mm wrench, 118 to 131 mm filter wrench

1. Operate engine until coolant reaches 60C [140F]; shut engine off.
2. Remove oil drain plug; drain oil into a 22 litre (23 U.S. quart) container.
3. Remove the filter using a 118 to 131 mm filter wrench.
4. Clean the gasket surface of the filter head.
5. Lubricate the new filter gasket and fill the filter with clean oil.
6. Install filter; install oil drain plug and tighten to 80 Nm [60 ft-lb].
7. Fill engine with clean 15W-40 oil to the proper level.
8. Idle engine, check for leaks, recheck oil level.

⚠ Do not engage the starting motor more than 30 seconds; wait two minutes between attempts

1. Disengage driven unit or put transmission in neutral.
2. Position fuel shutoff, electrical switch or control to run.
3. Industrial: set throttle at idle. Automotive: depress accelerator fully and release.
4. Engage starting motor; do not crank more than 30 seconds.
5. Wait two minutes between each attempt to start.
6. Engine oil pressure must be indicated within 15 seconds after starting.
7. When cold, increase engine speed slowly to stabilize oil pressure.
8. Idle 3 to 5 minutes at 1000 RPM before operating with a load.

⚠ Do not exceed the torque value given for the retaining nut; this is not the final torque value

Tools: 22 mm and 27 mm sockets, 75 mm T-bar puller, 15 mm and 24 mm wrenches, Torque wrench

1. Clean debris; remove fuel lines, control linkage and fuel shutoff solenoid.
2. Locate TDC cylinder 1; push TDC pin into camshaft gear hole.
3. Remove gear cover access cap; remove nut and washer from pump shaft.
4. Pull the drive gear loose from the shaft with a 75 mm T-bar puller.
5. Remove the four mounting nuts and remove the fuel pump.
6. Align pump timing pin; install pump with cylinder 1 at TDC.
7. Install mounting nuts 43 Nm [32 ft-lb]; retaining nut 10 to 15 Nm [7 to 11 ft-lb].
8. Disengage timing pin; tighten drive nut PES6A 93 Nm, PES6MW 105 Nm.

⚠ Cleanliness is an important consideration during repair of a diesel engine. Built-in contamination can reduce the life of an engine.

1. Observe all safety precautions noted in the procedures.
2. Provide a clean environment and follow the cleaning instructions specified in the procedures.
3. Perform the inspections specified in the procedures.
4. Replace worn and damaged parts as necessary for a successful rebuild.
5. Use genuine Cummins new or ReCon® service parts and assemblies.
6. Follow the specified disassembly and assembly procedures to avoid damaging parts and ensure proper assembly and tightening.

Tools: 10mm wrench, Torque wrench, Injector bore cleaning brush

1. Thoroughly clean around the injectors.
2. Disconnect the high pressure fuel lines and fuel drain manifold.
3. Remove the injectors.
4. Clean the injector nozzle bore with injector bore cleaning brush.
5. Lubricate the seating lips of the sleeve with anti-seize compound.
6. Install injector package with a new copper sealing washer; use only one washer.
7. Install the holddown capscrew; torque 24 Nm [18 ft-lb].
8. Install fuel drain manifold 8 Nm [6 ft-lb] and high pressure lines 24 Nm [18 ft-lb].

⚠ Do not let any debris fall into the thermostat cavity when cleaning gasket surfaces

Tools: 10, 18 and 19 mm wrenches

1. Drain 2 litres (2.1 U.S. Quarts) of coolant; remove radiator hose.
2. Remove the drive belt; disconnect the negative battery cable.
3. Loosen alternator link capscrew; remove mounting bolts and lower alternator.
4. Remove capscrews; remove the water outlet connection.
5. Remove thermostat housing and belt tensioner assembly.
6. Remove thermostats and clean gasket surfaces.
7. Install new thermostats and position a new gasket over them.
8. Install housing, outlet connection; tighten capscrews to 24 Nm [18 ft-lb].

⚠ New turbochargers must be prelubricated before start-up

⚠ Cover the opening if turbocharger is not immediately replaced

Tools: 10, 13, 15, 16 mm and 7/16-inch wrenches

1. Remove air crossover tube; disconnect intake and exhaust piping.
2. Remove the capscrews from the oil drain tube.
3. Remove the oil supply line.
4. Remove the exhaust clamp, turbocharger and gasket.
5. Clean sealing surface; apply anti-seize compound to mounting studs.
6. Install turbocharger with new gasket; torque 32 Nm [24 ft-lb].
7. Prelubricate new turbocharger with 50 to 60 cc [2 to 3 ounces] clean engine oil.
8. Install oil supply line 15 Nm [11 ft-lb] and drain tube 24 Nm [18 ft-lb].