TM 5-3895-346-14
TROUBLESHOOTING (ENGINE)
ENGINE OVERHAUL
1.
Start the engine and run it at approximately one-half rated load until normal operating temperature
is reached.
2.
Stop the engine and remove the fuel pipes from the injector and fuel connectors of the No. 1
cylinder.
3.
Remove the injector and install adaptor J 7915-02 and pressure gage and hose assembly J 6692
(Fig. 1).
4.
Use a spare fuel pipe to fabricate a jumper connection between the fuel inlet and return manifold
connectors. This will permit fuel from the inlet manifold to flow directly to the return manifold.
5.
Start the engine and run it at a 600 rpm. Observe and record the compression pressure indicated
on the gage.
NOTE
Do not crank the engine with the starting motor to obtain the compression
pressure.
Figure 1. Checking Compression Pressure
6.
Perform steps 2 through 5 on each cylinder. The compression pressure in any one cylinder at a
given altitude above sea level should not be less than the minimum shown in Table 1. In addition, the variation
in compression pressures between cylinders must not exceed 25 psi (172 kPa) at 600 rpm.
EXAMPLE
If the compression pressure readings were as shown in Table 2, it would be evident
that No. 3 cylinder should be examined and the cause of the low compression
pressure be determined and corrected.
The pressures in Table 2 are for an Engine operating at an altitude near sea level. Note that all of the cylinder
pressures are above the low limit for satisfactory engine operation. Nevertheless, the No. 3 cylinder
compression pressure indicates that something unusual has occurred and that a localized pressure leak has
developed.
Low compression pressure may result from any one of several causes:
A.
Piston rings may be stuck or broken. To determine the condition of the rings, remove the air box
cover and inspect them by pressing on the rings with a blunt tool. A broken or stuck ring will not have a spring-
like action.
TABLE 2
Cylinder
Gage Reading
psi
kPa
1
525
3 617
2
520
3 5&3
3
485
3 342
4
515
3 548
442
