Mityvac MV5535 Digital Diesel Compression Test Kit - Manual (Page 5)

Page Number - 5 Form 823637
Always read instructions carefully prior to use.
Safety Information
• Read and understand all safety precautions and operat-
ing instructions contained in this manual.
• Always wear eye protection when performing a compres-
sion test.
• Do not exceed the maximum rating of the tester; 1000
psi (69 bar) (6,900 kPa)
• Prior to testing, set the gearbox to neutral on all vehicles
or machinery having a standard transmission, or park for
automatic transmissions.
• Prior to engaging ignition, ensure that the fuel supply is
disabled using manufacturer’s recommended method.
• Make sure that all connections are secure prior to test-
ing.
• Take precautions to avoid contact with hot engine sur-
faces.
Included in this Kit
• Digital Diesel Compression Tester comprising of test
gauge with rubber boot, 15” (375mm) long, high pres-
sure hose, and 90° x 180° swivel female quick release
coupler.
Injector Adapter (Dodge 24 valve 5.9 Cummins (1999-
2003), 5.9L Cummins ISB and ISBE)
Injector Adapter (Case/Cummins Series “B” 2.9L, 3.9L,
5.9L through 1998)
Glow Plug Adapter (GM 4.3L, 5.7L, (1978 to 1985),
Navistart 6.9L, 6.3L up to 1994)
Glow Plug Adapter (GM 6.2L & 6.5L V*)
Glow Plug Adapter (Navistar 7.3L Power Stroke)
Glow Plug Adapter (Volkswagen 1.9L TDI)
Custom Molded Case
User’s Manual (English, French, Spanish, German)
Functional Overview
The Mityvac Digital Diesel Compression Tester is designed
for testing the compression produced in the cylinders of a
diesel engine. It can measure, display, and store compres-
sion values of up to 1,000 psi (69 bar) (6,900 kPa) for up to
12 cylinders.
When using this tester to perform a compression test on a
cylinder, the current peak compression value is displayed
in larger numbers at the center of the LCD. This value
is automatically transferred to memory, and displayed in
smaller numbers at the bottom right of the display. When
the pressure relief button is depressed, the current com-
pression reading returns to zero, but the peak value is
retained in memory and continues to be displayed in the
bottom right corner of the LCD. Repeated tests can be
run on the same cylinder, and the new current peak value
will be displayed by the larger numbers. This new peak
value will not be retained in memory unless it surpasses
the value of the previous test, or the CLEAR button was
pressed to erase the old value from memory.
Peak compression values can be stored for up to 12 cylin-
ders. Each value is displayed on the LCD along with the
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cylinder number. During and/or after completion of testing
all cylinders, the peak values can be reviewed by press-
ing the CYLINDER button to scroll through the memory.
Individual peak values can be erased from memory by
pressing the CLEAR button when the appropriate cylinder
and value are displayed. Pressing the CLEAR button for 3
seconds at any time will clear the memory for all cylinders
and return the display to cylinder 1.
Before Running a Compression Test
• To achieve accurate results, the engine should be run
until it reaches normal operating temperature, prior to
testing. Testing should be completed before the engine
cools.
• Ensure battery(s) are fully charged to provide power for
adequate cranking speed. Check engine manufactur-
er’s specifications to determine if a minimum cranking
speed is required. It is recommended that a charger be
connected, or a backup or auxiliary battery be used to
maintain required cranking speed.
Performing a Compression Test
Diesel engines utilize either a direct or indirect fuel injec-
tion system. Direct injection engines inject fuel directly into
the cylinder, while indirect injection engines use a small
pre-combustion chamber. Spark plugs are not required for
either type of diesel engine. Instead, the high compression
achieved in a diesel engine cylinder heats the air, which
ignites the fuel. However, a cold diesel engine requires a
means to preheat the air in the cylinder, pre-combustion
chamber or manifold, to facilitate starting. This is most of-
ten accomplished with a glow plug. Depending on whether
the engine has a glow plug, and its location, will determine
whether a glow plug adapter or injector adapter is required
for compression testing. The best way to determine the
type of adapter to use, and the appropriate test method is
to consult a service manual. A full line of glow plug and
injector style test adapters for most makes and models of
vehicles and heavy equipment are available from Mityvac.
Testing with Glow Plug Adapter
Prior to starting a compression test, consult manufacturer’s
specifications and/or appropriate service manual to deter-
mine the correct procedure for performing the compression
test. Familiarize yourself with the proper specifications and
any unique testing procedures, and follow the recommend-
ed procedures for removing and installing the glow plugs.
1. Put the vehicle in neutral or park, and set the parking
brake.
2. Run the engine to normal operating temperature.
3. Ensure the battery has a full charge and/or connect a
charger or auxiliary battery.
4. Thoroughly clean the area around each glow plug to
eliminate any chance of dirt or contamination entering
the engine.
5. Remove the glow plugs, label them by cylinder number,
and protect them from damage.
6. Disable the fuel supply system.
7. Select the appropriate glow plug adapter and install it
into cylinder 1.
8. Turn on the compression tester by pressing the ON/