TOPIC 16. ENGINE RUN-IN SCHEDULE

TM 10-3930-644-14&P

TOPIC 16. ENGINE RUN-IN SCHEDULE

A. PURPOSE

6. Check ammeter. If not functioning correctly,

After installation of new engine, or one in which new

check electrical system for grounds, shorts or

pistons and piston rings have been installed engine must

loose connections.

be run-in to allow piston rings to seat and avoid

possibility of cylinder bore scoring and excessive oil

7. Check engine timing. Refer to FUEL SYSTEM

consumption.

When engine is first started after

Section.

installation of new pistons and piston rings, excessive

smoke, raw fuel and lubricating oil may appear in the

8. After engine has reached normal operating

exhaust. This condition should correct itself as engine is

temperature, remove valve chamber cover and

run-in.

check valve clearances.

Test run engine after overhaul and make adjustments as

9. A run-in period of six to eight hours is

are found necessary for smooth and efficient engine

recommended. Start with no load and gradually

operation.

increase engine load until operating at full load

for the last two hours.

B. TEST RUN CHECKS

10. At end of run-in gradually slow down engine and

The following procedure is recommended with engine

allow it to idle for a few minutes, allowing engine

installed in truck.

to cool gradually.

11. Torque cylinder head capscrews.

CAUTION

Ensure engine has been cleared of all

12. Recheck crankcase oil level and any points of

rags, tools, parts, oil, water, etc.,

adjustment, making necessary corrections.

prior to engine run-in.

1. Fill crankcase to correct oil level with oil

13. Warm up engine to operating temperature. Blow

specified in Maintenance Module, LUBRICANT

dirt out of pockets around spark plugs, remove

AND FUEL SPECIFICATIONS.

plugs, and insert compression gauge in first

spark plug hole, holding it firmly. Crank engine

2. Fill cooling system with proper coolant for

until the highest gauge reading is obtained.

summer or winter operation. Refer to COOLING

(Approximately four compression strokes).

SYSTEM Section.

Check all cylinders in this manner. If readings

are low in two adjacent cylinders, a blown head

3. Inspect air cleaner to determine if properly

gasket is indicated. If readings are low and vary

serviced. Lubricate all points where lubrication

widely (more than 10 PSI), pressure is being lost

is required.

either at the pistons, rings or valves.

determine where pressure loss is occurring,

4. Start engine and allow to run at approximately

Insert about one tablespoon of SAE 30 engine

600-700 R.P.M. Check for oil, fuel or coolant

oil through the spark plug hole. Take a new

leaks. Check coolant and oil levels. If engine is

reading. If this reading is higher than the initial

run indoors, pipe exhaust gases outside.

reading, the piston rings are faulty. If reading is

the same as the initial reading, the valves may

5. Check oil pressure gauge. If gauge does not

be leaking or the cylinder head gasket is

damaged.

stop engine at once and refer to TROUBLE

SHOOTING Section.

R-104-1

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