D330, D333, 3304, 3306 – Checking Inlet Manifold Pressure At Engine Full Load And Speed

4S6553 Instrument Group.
Checking inlet manifold pressure (frequently referred to as “boost”) at engine FULL LOAD and speed (governor balance point), provides a convenient test of engine performance. To check inlet manifold pressure, some method of controlling the load on the engine must be provided. The preferred method is by using a dynamometer.

Using the 4S6553 Instrument Group, proceed as follows:

1. Connect the manifold pressure gauge to the inlet manifold.

1. Location to check inlet manifold pressure.

2. Connect the tachometer to the engine to locate the full load rpm (governor balance point).

NOTE: At the balance point, rack position and the injection pump speeds are such that maximum fuel is delivered to the engine, turbocharger speed is maximum, and inlet manifold pressure is maximum.

3. With the governor control moved to FULL LOAD position, load the engine until rpm stabilizes. Slowly decrease the load (allowing engine rpm to increase) while simultaneously observing the rise in inlet manifold pressure.

NOTE: Inlet manifold pressure will rise (as load is decreased), reach a peak, and fall sharply. Watch for the pressure peak and note the rpm at which it occurs. This rpm is the governor balance point.

4. Record the engine rpm and inlet manifold pressure.

5. Return governor control to LOW IDLE.

6. Compare the recorded information, engine rpm and inlet manifold pressure, with the values listed in the RACK SETTING INFORMATION.

7. If full load rpm and/or inlet manifold pressure are outside their limits, determine the cause and correct. See topic PROBLEM SOLVING.

8. If stall speed is within limits, but boost is not, determine why and correct.

9. If boost and/or stall speed are outside their limits, determine cause as either a converter or engine malfunction and correct.

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