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Keep for Future Reference
UM-MFK-0007-V2
Cylinder Compression
Test Kit
Instruction Manual
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Disclaimer
Read this disclaimer completely and carefully before
proceeding with the rest of the manual content.
1. Product Modifications
Any modifications or alterations to Orion Motor Tech (OMT)
products void any warranties and may result in damage or
injury. OMT shall not be liable for any damages resulting
from such modifications or alterations.
2. Compliance with Laws
Customers shall be liable for ensuring that the use of
OMT products complies with all applicable laws and
regulations in their respective jurisdictions. OMT shall not
be responsible for any violations of laws or regulations
resulting from the use of OMT products.
3. Correct Use
Always use OMT products only as directed in the
accompanying manuals. Failure to follow instructions may
result in injury or damage.
Always ensure the assembly, installation, operation,
maintenance, or repair of OMT products is carried out by
a competent person.
Regular maintenance should be performed throughout
the lifecycle of OMT products. You are responsible for
ensuring the products operate as intended.
Always wear appropriate protective gear.
4. Third-Party Products
OMT shall not be liable for any damages or losses
resulting from the use of third-party products in
conjunction with OMT products. Customers shall refer to
the third-party's guidelines and/or warranties (if any) for
any third-party products used.
5. Limitation of Liability
OMT shall not be liable for any direct, indirect, punitive,
incidental, special, or consequential damages to property
or life, whatsoever arising out of or connected with the
use or misuse of OMT products. In no event shall OMT’s
liability exceed the value of the products sold.
6. Warranty
Refer to the sales page for warranty information.
This disclaimer states the entire obligation of OMT with
respect to OMT products. If any part of this disclaimer is
determined to be void, invalid, unenforceable, or illegal,
including but not limited to the warranty disclaimers, liability
disclaimers, and liability limitations set forth above, the invalid
or unenforceable provision will be deemed superseded by
a valid and enforceable provision that most closely matches
the intent of the original provision and the remainder of the
agreement shall remain in full force and effect.
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• The instructions provided herein are only for general information. ALWAYS perform all repairs in full compliance with
your vehicle’s service manual. After any repair, test your engine and vehicle in your workshop and at low speed before
returning to normal use. Failure to do so may result in serious property damage and severe personal injury.
• ONLY use this product for its intended purpose, testing the vehicular cylinder compression.
• DO NOT allow use by children, by persons whose mental or physical condition precludes safe use, or by persons
unfamiliar with this product and its compatible vehicle systems.
• DO NOT use while under the influence of alcohol, drugs, or any medication that negatively affects your judgment or
reflexes. Keep children and bystanders away during use.
• Excessive pressure and/or unclean air will damage the tester and may cause property damage and/or personal injury.
• Keep hoses away from heat, oil, and sharp edges. ALWAYS check for secure hose connections during use.
• ALWAYS make sure there are no open flames and other fire hazards nearby before working on fuel systems. DO NOT
smoke during use. Only use explosion-proof drop lighting for any additional illumination during testing. Have a dry
chemical fire extinguisher available and familiarize yourself with its correct range before use. Take care not to use the
extinguisher too close to the flame, as its high pressure can produce blowback.
• Keep your work site clean and well-lit. Cluttered and dark work areas invite accidents. For best results, keep the kit
clean and dry. Remove any fluid, oil, or grease before and after work.
• ALWAYS use personal protective equipment (PPE) suitable to your task. Always wear ANSI and OSHA-approved eye,
breathing, and hand protection while using this product. Normal use of this product typically produces microscopic
particles known to the state of California to cause cancer, birth defects, or other reproductive harm. Nonslip footwear is
also highly recommended.
• Other equipment such as ear, head, and body protection may also be necessary depending on your work, work
environment, and other equipment.
• Dress properly for automotive servicing. DO NOT wear loose clothing or jewelry and keep hair, clothing, gloves, hoses,
and tools away from any moving parts during use.
• ALWAYS know and understand the specific safety warnings and instructions for your vehicle before using this kit. Use
the correct fluids, pressures, adapters, etc. for your vehicle. Make sure the vehicle is fully supported and parked before
beginning any work. Take care to never touch any heated surface with exposed skin.
• ALWAYS ensure that your vehicle has been jacked up and is adequately supported with axle stands.
• DO NOT perform compression testing on diesel engines. The higher compression in a diesel engine may cause engine
damage.
• DO NOT overreach. Keep proper footing and balance at all times.
• NEVER scrape the hose or drop the pressure gauge on hard or rough surfaces.
• In case of an accident or injury, have a first aid kit and a communication device (e.g., a phone) readily available. Know
the location of emergency medical facilities.
• Maintain this product. Check for misalignment, binding, wear, or other damage before use. If any damage is detected,
repair or replace the problematic components before further use. In a large shop, mark such tools “DO NOT USE” until
they have been repaired. ONLY replace components with identical parts.
• Automotive repair is an inherently dangerous activity. This manual and the separate vehicle service manual cannot
cover all possible situations that may arise. ALWAYS exercise discretion and good judgment. Seek training if needed.
Safety Information
2
Specifications
Gauge Diameter 2.5 in. 63 mm
Pressure Scale 50–300 psi
3–21 kg/cm²
3–20 Bar
Hose Fittings 0.4, 0.5, 0.6, & 0.7 in. 10, 12, 14, 16, & 18 mm
Air Release Type Push Button
Extension Rod
Length 7.5 in. 19 cm
Thread M14 × 1.25
Hose Length
Length 16.9 in. 43 cm
Threads M14 × 1.25 & M18 × 1.5
Parts List
No. Item Qty.
A Hose 1
B Pressure Gauge 1
C Extension Rod 1
D Push-On Connectors 2
E Spark Plug Tester 1
F 10 mm Adapter 1
G 12 mm Adapter 1
H 14 mm Adapter 1
I 16 mm Adapter 1
J 18 mm Adapter 1
K Valve Cores 2
L Spare O-Rings 5
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Operation
• Park your machinery in a level place safely and engage the
parking brake. If necessary, chock the wheels/tracks.
• Use correct tools and personal protective equipment (PPE)
before performing any operation. Be extremely careful with
possible pinching points, moving parts, or parts that may
suddenly spring out.
• Performing a pressure test requires the work of two
individuals; one person to operate the machinery’s ignition
switch and the other person to read the gauge.
• For an abundance of safety, we recommend you take training
before using these tools. Serious injury could happen due to
a lack of training.
• If the dial pointer is not at zero, use a flathead screwdriver
to turn the zero-adjustment knob counterclockwise until the
pointer returns to zero.
Cylinder Compression Test
1. Run your vehicle's engine in a well-ventilated location until it reaches its normal operating temperature.
2. Stop the engine, wear protective work gloves, and disconnect all spark plug wires. Keep them
in order, numbering them according to the cylinder from which they were removed.
3. Loosen all spark plugs by about half a turn, but do not remove them.
4. Remove all the dirt and debris from the spark plug wells using an air hose or wire brush.
5. Remove the spark plugs and arrange them on a clean, flat surface, numbering them according
to the cylinder from which they were removed.
6. Remove the air filter and set the throttle plates to their wide-open position. Make sure not to
damage the linkage or throttle components.
7. Disconnect the ignition system according to your vehicle's manual instructions.
8. Either connect one of the push-on connectors straight
to the gauge coupling for quick installation or select
the spark plug adapter that fits your vehicle. Screw the
adapter into the provided hose and screw the spark plug
adapter and hose assembly into a spark plug well by hand.
For hard-to-reach spark plugs, screw the provided
extension rod into the hose and screw the adapter
onto the other end of the rod.
DO NOT use a wrench, which can easily cause
damage from overtightening.
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9. Connect the coupling on the gauge to the hose. Make sure it's fully engaged.
10. Use a remote starter or a second person to crank the engine for at least five compression
strokes or until the pressure reading on the gauge stops rising.
The gauge needle should travel up the scale on each compression stroke until it reaches a
peak value.
If the gauge needle does not travel up the scale or remains at the same value for several
strokes and then starts to climb, a valve may be sticking. Clean any sticky valves as needed.
If the compression reading exceeds the vehicle manufacturer's specification and the piston
and cylinder have not been modified, access the cylinder head to check it for carbon build-up.
Remove any such build-up and rerun the test.
11. Record the stabilized compression reading,
stop the engine, and then push the
release valve on the side of the gauge's
connection to relieve the pressure.
12. Repeat the test and record the new reading as well. Relieve the pressure again and remove
the hose and adapter from the spark plug well.
13. Repeat the process for the other cylinders. All cylinders should indicate pressure within the
vehicle manufacturer's specifications, and the readings should not vary by more than 10% from
test to test or cylinder to cylinder.
If a reading on two adjacent cylinders is at least 20 psi lower than the others, check for any
oil or coolant in the cylinder head, indicating a blown head gasket or cracked cylinder head. If
so, replace the broken part and rerun the tests.
If the readings are all low or vary widely between cylinders, pour a teaspoon of SAE 30 oil
into each cylinder and retest them. If the readings increase considerably, the problem may
be poorly seated or worn piston rings. If the readings remain the same, the valves and/or
associated components, such as a burned or damaged piston, maybe the problem. Check and
repair or replace any problematic parts.
14. After correcting any problems, clean, recap, and reinstall the spark plugs in the same order
they were removed or install new ones.
15. Reconnect each spark plug wire.
16. Return the throttle plates to the closed position and replace the air filter.
17. Reconnect the ignition system wiring.
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Spark Plug Test
1. Disconnect the negative terminal from your vehicle's battery.
2. Disconnect the spark plug wire from one of your vehicle's spark plugs.
3. Mount the spark plug tester's prong to the wire.
4. Connect the other end of the tester to the spark plug.
5. Reconnect the negative terminal on the battery.
6. Use a remote starter or have a second person start the engine while you observe the tester.
7. If the cylinder is not in issue, the tester's light will begin flashing. If it doesn't come on,
disconnect the negative terminal on the battery again and replace the ignition wire before
continuing.
8. Once the tester's light is flashing properly, observe the tester while the engine idles for a few
minutes. If the tester goes dim or its rate of flashing changes, the engine might be misfiring
due to a faulty spark plug or coil. Check your coil with an ignition coil tester (not incl.) to see
whether the coil or the spark plug is the problem. Replace whichever part is broken.
9. Reconnect the spark plug wire to the spark plug.
10. Repeat the steps above with the other spark plugs.
Maintenance
• Check the condition of these tools before and after each use. Before further use, repair or
replace any worn or damaged components.
• The exterior of these tools can be cleaned with a soft, damp cloth. Do not use abrasive cleaners
or caustic chemicals. Allow time for the tools to air dry before replacing them in the case.
• Store this product in a cool, dry place away from direct sunlight and inaccessible to children.
User Manual
Rev. 30 May 2025
