Cummins/Onan P248 Generator Set

Tools: 1/8 inch drill bit, wrench

1. Shut off engine, remove air cleaner outer cover and filter element.
2. Loosen choke rod swivel clamp screw.
3. Lock throttle control lever with pin (1/8 inch drill bit) so pin acts as stop for choke lever.
4. Push choke rod towards carburetor to fully open choke.
5. Rotate choke lever towards carburetor until it bears against pin stop, tighten swivel clamp screw.
6. Remove lock pin and check choke linkage operation. Replace damaged components.
7. Reassemble air cleaner.
8. Adjust throttle and choke control cables.

Tools: 1/8 inch drill bit, wrench

1. For single-cable: shut off engine, loosen throttle cable clamp.
2. Lock throttle lever with pin (1/8 inch drill bit).
3. Push speed control lever to high speed position.
4. Hook cable wire into throttle lever, pull out slack, tighten clamp. Remove lock pin.
5. For two-cable: repeat steps 1-3, then push choke knob to full-open.
6. Hook choke cable wire into choke lever, push choke rod towards carburetor, pull out slack, tighten clamp.

Tools: torque wrench, shims

1. Tighten the oil base to the torque recommended in Section 4 Assembly.
2. Check the crankshaft endplay and compare it with Section 3 Dimensions and Clearances.
3. If endplay exceeds the specified limits, remove the oil base and add shim(s) between the thrust washer and the oil base.
4. Install the oil base, making sure the thrust washer and shim notches line up with the lock pins.
5. Torque the oil base and check the endplay again.

⚠ Adjusting the engine speed to a value above that specified by the equipment manufacturer could cause the equipment to operate at speeds in violation of Federal and State Standards for Safety for the equipment.

⚠ Moving parts can cause severe personal injury or death. Take care when measuring engine speed with a tachometer and follow the meter instructions. You must be a qualified mechanic.

Tools: tachometer

1. Normally no need to adjust engine speed. Instructions are for equipment manufacturer. Attempt only by qualified mechanic using accurate tachometer.
2. Set low-idle and high-idle speeds to values specified in equipment Operator's Manual. If absent, adjust low-idle to 1,100 RPM and high-idle to 3,400 RPM.
3. Start engine, observing all equipment manufacturer's instructions and precautions.
4. If throttle cable already connected, loosen clamp at engine and back out low-idle speed stop screw so speed stop screw on carburetor touches its stop. Adjust engine speed to 1,000 RPM with carburetor
5. Turn low-idle speed stop screw to obtain specified low-idle speed.
6. Move engine throttle link up against its stop tang and hold it there while bending tang as necessary to obtain specified high-idle speed.
7. Hook engine throttle link with throttle cable, pull slack out of throttle cable and tighten clamp. Check for full, smooth movement of engine throttle link between its two stop positions when equipment

⚠ Adjusting engine speed above equipment manufacturer spec could cause violation of safety standards.

⚠ Moving parts can cause severe personal injury or death.

Tools: tachometer, 1/8 inch drill bit, wrench

1. Remove outer cover of air cleaner and set up tachometer.
2. Start engine.
3. Lock throttle control lever with pin (1/8 inch drill bit) in control plate.
4. Loosen choke rod swivel clamp screw and push choke rod towards carburetor to fully open choke.
5. Adjust high-idle speed by rotating engine control plate. Loosen pivot bolt 1/8 turn and set bolt 1/4 turn. Retighten.
6. Adjust low-idle speed by turning idle speed screw. Remove lock pin and move throttle to lowest position.
7. Shut off engine and readjust choke.

Tools: feeler gauge, 7/16-inch open end wrench, 9/16 inch (14 mm) open end wrench, torque wrench

1. Remove the ignition key to prevent accidental starting.
2. Remove all parts necessary to gain access to the valve tappets.
3. Remove the spark plugs to ease turning the engine over by hand.
4. Rotate the crankshaft clockwise until the right intake valve opens and closes.
5. Continue turning until the flywheel timing mark lines up with the governor shaft on the gear cover.
6. Verify the left intake and exhaust valves are closed and there is no pressure on the valve lifters.
7. Check that the correct feeler gauge passes freely between valve cap and tappet; a 0.002 inch thicker gauge should not.
8. Turn the adjusting screw with a 7/16-inch open end wrench to obtain correct clearance; hold the tappet with a 9/16 inch (14 mm) wrench.
9. For the left cylinder, turn the engine one complete revolution, line up the timing marks, and repeat.
10. Replace all removed parts, tighten all screws securely, and torque valve cover bolts to specification.

Tools: Plastigauge, torque wrench

1. Make certain all parts are marked or identified so they are installed in their original positions.
2. Using a clean, dry cloth, thoroughly clean all oil from the crankshaft journal and the connecting rod.
3. Place a piece of correct size Plastigauge in the bearing cap the full width of the journal surface and about 1/4 inch (6.35 mm) off center.
4. Rotate the crankshaft about 30 degrees from bottom dead center and reinstall the bearing cap.
5. Tighten the rod bolts to the torque specified in Section 4 Assembly; do not turn the crankshaft.
6. Remove the bearing cap; the flattened Plastigauge will adhere to either the bearing cap or the crankshaft.
7. Compare the flattened Plastigauge with the graduations on the Plastigauge envelope to determine the clearance.

⚠ Reversing positive and negative battery connections or allowing the engine to run without being connected to the alternator will result in engine electrical system damage.

Tools: volt-ohmmeter, such as the Simpson 370, DC voltmeter

1. Check the battery voltage with the engine not running; charge the battery if not within Table 8-1 specifications.
2. With the engine running, check battery terminal voltage (regulator output) using a DC voltmeter.
3. If voltage is greater than specified, replace the regulator-rectifier assembly; if less than specified, proceed to Step 3.
4. Examine all wires for loose, corroded, or broken connections and check fuses; repair as needed to assure complete circuits.
5. Disconnect the plug from the regulator-rectifier and test AC voltage at the plug with the engine running.
6. If AC voltage is as specified but DC voltage is low, replace the regulator-rectifier.
7. Use the Rx1 scale on the ohmmeter to detect an open or ground in the stator (engine not running); the reading to ground should show no continuity.
8. Connect one ohmmeter lead to each wire from the stator and check resistance; replace the stator if not as specified.
9. If stator resistance is as specified and windings are not shorted or open, low AC voltage may be due to loss of magnetism; replace the blower wheel assembly.

⚠ Ignition of fuel can result in severe personal injury or death. Thoroughly clean up any spilled fuel. Do not smoke or allow any source of ignition near the work area.

Tools: vacuum gauge, pressure gauge, fuel hose, clamps

1. Operate the engine at idle for five minutes to ensure the carburetor is full of fuel.
2. Shut the engine off and remove the fuel inlet line from the fuel pump.
3. Connect a vacuum gauge to the pump inlet using a piece of fuel hose with clamps.
4. Start the engine and idle for at least five seconds; record the vacuum gauge reading.
5. Move the throttle to high idle position, wait at least five seconds, and record the vacuum reading.
6. Shut off the engine, remove the vacuum gauge hose, and connect the fuel inlet line.
7. Remove the fuel outlet line and connect a pressure gauge using fuel hose with clamps.
8. Start the engine and idle at least five seconds; hold the pressure gauge level with the pump outlet and record the reading.
9. Move the throttle to high idle, wait five seconds, and record the pressure reading.
10. Remove the pressure gauge hose and reconnect the fuel outlet line. Replace the pump if readings are not within Table 7-1.

Tools: Simpson 260 VOM or equivalent

1. Make sure the ignition power is off and the coil is at room temperature [70 F (21 C)].
2. Use a Simpson 260 VOM or equivalent.
3. Place the black lead on the negative (-) coil terminal and the red lead on the positive (+) coil terminal; primary resistance should read between 2.90 and 3.60 ohms.
4. Change the resistance setting; place ohmmeter leads inside the spark plug cable holes; secondary resistance should read between 14,500 and 19,800 ohms.
5. If either resistance is not within specification, replace the coil.

⚠ The electronic ignition produces voltage which can cause electrical shock. Do not touch electrical components or wires while ignition is on.

⚠ Accidental starting of the engine can result in severe personal injury or death. Remove spark plugs before proceeding.

⚠ Ignition of cylinder gases can cause severe personal injury. Ground spark tester away from spark plug holes.

Tools: spark tester, jumper lead, 12-volt test light

1. Check all electrical connections to be sure they are clean and tight; if good, go to Step 2.
2. Test the ignition coil for proper resistance; if good, go to Step 3.
3. Pull the spark plug wires off the spark plugs and remove the spark plugs.
4. Connect an approved spark tester to each spark plug wire and ground them away from the spark plug holes.
5. Turn the key on and crank the engine for 5 seconds while watching for spark; regular spark means the problem is not in the ignition system.
6. Connect a jumper lead from the positive battery terminal to the positive (+) coil terminal (smaller diameter post) and crank while watching for spark.
7. If no spark, connect the positive probe of a 12-volt test light to the negative (-) coil terminal (larger post) and the negative probe to a good engine ground.
8. Turn the key to START; the test light should flash on and off; if it stays on or does not light, replace the ignition module.
9. If the trigger ring was removed, reinstall it with the part number side readable (facing the flywheel); do not push the ring up against the seal.
10. Install the spark plugs and wires; connect the red lead from a new module to the positive (+) coil terminal and the black lead to the negative (-) terminal.

⚠ Accidental starting of the engine can result in severe personal injury or death. Remove spark plugs before proceeding.

⚠ The electronic ignition produces voltage which can cause electrical shock. Do not touch electrical components or wires while ignition is on.

Tools: voltmeter

1. Pull the spark plug wires off the spark plugs and remove the spark plugs.
2. Turn the ignition on.
3. Connect a voltmeter between the negative (-) coil terminal (larger post) and a good engine ground.
4. Rotate the flywheel slowly by hand clockwise until the voltmeter reading switches from approximately 1 volt to battery voltage.
5. At this point one of the chaff screen bolts should lie between the two timing marks on the blower housing.
6. To recheck, rotate the flywheel another complete revolution clockwise; moving the flywheel back and forth will not activate the ignition control.
7. Install the spark plugs and wires.