1. SAFETY
WARNING! Ensure Health & Safety, local authority and general workshop practice regulations are adhered to when using this equipment.
8 DO NOT use tools if seals or threads are damaged. Any defective seal MUST be changed before use to avoid incorrect readings.
9 Maintain tools in good and clean condition for best and safest performance.
9 Ensure that a vehicle which has been jacked up is adequately supported with axle stands.
9 Wear approved eye protection. A full range of personal safety equipment is available from your Sealey stockist.
9 Wear suitable clothing to avoid snagging. DO NOT wear jewellery and tie back long hair.
9 Ensure any disconnected fuel pipes are plugged to avoid spillage.
9 Ensure that the correct connector is used for the engine being tested.
WARNING! Always release the pressure from the gauge before disconnecting the coupling.
9 Account for all tools, and parts being used and DO NOT leave them in or near the engine.
IMPORTANT: Always refer to the vehicle manufacturer’s service instructions, or a proprietary manual, to establish the current procedure
and data.
WARNING: The warnings, cautions and instructions discussed in this instruction manual cannot cover all possible conditions and
situations that may occur. It must be understood that common sense and caution are factors which cannot be built into this product, but
must be applied by the operator.
2. INTRODUCTION
Real-time compression pressure readings. Easy-to-read digital display. 2.8-inch backlit display. Pressure units – PSI, bar, kg/cm².
Auto power o. The set includes four extension hoses, ve plug thread adaptors from 10 to 18mm and a self-sealing quick connector.
Suitable for most petrol engine cars and light commercials. Supplied in storage case.
3. SPECIFICATION
4. FEATURES
DIGITAL COMPRESSION TEST KIT 10PC
Thank you for purchasing a Sealey product. Manufactured to a high standard, this product will, if used according to these
instructions, and properly maintained, give you years of trouble free performance.
IMPORTANT: PLEASE READ THESE INSTRUCTIONS CAREFULLY. NOTE THE SAFE OPERATIONAL REQUIREMENTS, WARNINGS & CAUTIONS. USE
THE PRODUCT CORRECTLY AND WITH CARE FOR THE PURPOSE FOR WHICH IT IS INTENDED. FAILURE TO DO SO MAY CAUSE DAMAGE AND/OR
PERSONAL INJURY AND WILL INVALIDATE THE WARRANTY. KEEP THESE INSTRUCTIONS SAFE FOR FUTURE USE.
VS956 Issue 2 11/03/25
Original Language Version
© Jack Sealey Limited
Refer to
instructions
MODEL NO: VS956
Wear eye
protection
Model No: VS956
Nett Weight: 1.5kg
Operating Temperature: -10 to 60°C
Operating Voltage: 6V
Pressure units: PSI, bar, kg/cm²
Accuracy: 0.5% FS
Range: 0 to 435psi (0 to 30 bar)
Resolution: 0.01bar, 0.01kg/cm²,
0.01psi.
Battery: AAA x4 (not supplied)
Overload Pressure: 580psi (40bar)
Hose Length: 1150mm
Contents: M10x1.0, M12x1.25, M14x1.25, M16x1.5, M18x1.5mm, Straight
extension with safety lock, Flexible extension with safety lock,
Angled extension with rubber stop, Straight extension with
rubber stop.
A Display
B Press to save cylinder data; B Long press to lock/unlock the interface
C Pressure units convert
D Click press: interface data clearing; D Long press: pressure zeroing
E Press to switch temperature units; Long press to turn on/o the instrument
F Measuring Probe
G Press to turn on/o the key tone
H Press to turn on/o the backlight
I Battery Cover
A
B
D
g.A
C
E
G
H
I
F
4.1. INTERFACE DISPLAY
5. OPERATION
5.1. BATTERY INSTALLATION (FIG.3)
5.1.1. Remove rear battery cover by unscrewing the case screw.
5.1.2. Insert batteries (4x1.5VAAA). See next step.
5.1.3. Slide the at, negative end of the battery against the spring onto the
device. Then, push the raised, positive end into the at side of the
compartment.
5.1.4. Replace battery cover and screw in the case screw.
5.2. OPERATIONS
5.2.1. Press the (E) button for more than 2 seconds to start the instrument.
(FIG.A).
5.2.2. Press the (D) button to zero the display. (FIG.A).
5.2.3. Select the adapter suitable for the vehicle, connect it to the hardware
cable. (FIG.2).
5.2.4. Connect to the engine.
5.2.5. Press the (D) button to clear the data. This will reset to zero. (FIG.A).
5.2.6. Press the (C) button to switch between pressure units. (FIG.A).
5.2.7. Press the (D) button to switch between temperature units. (FIG.A).
5.3. START MEASURING COMPRESSION
5.3.1. First start the engine and run it to normal working temperature, stop the
engine and remove all the spark plugs.
5.3.2. With the throttled-wide open, screw the connector of the pressure gauge
into the spark plug hole, or remove the spark plug and select a suitable
adapter, connect the adapter to the installation position of the spark plug,
conrm that the pressure gauge, adapter and spark plug interface are
installed tightly without leakage.
5.3.3. Cut o the fuel supply, use the starter motor to drive the engine to rotate
at 100-150r/min for 3-5 seconds.
5.3.4. The gauge will show compression value.
5.4. DATA SAVING
5.4.1. When the current data is saved for the rst time, the measurement data
will be displayed in CYL PRESSURE; Click the (B) button, the current
average pressure value will be saved in CYL1. (FIG.A).
5.4.2. Save the current data for the second time, the measurement data will be
displayed in CYL PRESSURE; Click the (B) button, the current average
pressure value will be saved in CYL2. (FIG.A).
5.4.3. With such operations, according to the measurement sequence of each
cylinder of the engine, the current average pressure value data is saved
six times.
5.4.4. After the measurement is completed, press (E) button for 2 seconds to
shut down (it is required to be conducted under atmospheric pressure).
(FIG.A).
5.4.5. The device will automatically power o after 5 minutes of inactivity.
6. MAINTENANCE
6.1. GENERAL
To maintain the performance and appearance of the product, it is
recommended that the following product care guidelines be read
carefully:
6.1.1. Regularly check the product parts that need to be tightened and
connected.
If found loose, tighten to ensure the safe operation of the equipment.
6.1.2. The external and internal parts of the equipment in contact with various
VS956 Issue 2 11/03/25
Original Language Version
© Jack Sealey Limited
PRESSURE Real-time pressure value
AVG PRESSURE
(average pressure)
Average pressure value
TEMP Current Temp
TIME Measuring time
CYL PRESSURE
(cylinder pressure)
Cylinder pressure value
CYL1(cylinder 1) Pressure value of cylinder 1
CYL2(cylinder 2) Pressure value of cylinder 2
CYL3(cylinder 3) Pressure value of cylinder 3
CYL4(cylinder 4) Pressure value of cylinder 4
CYL5(cylinder 5) Pressure value of cylinder 5
CYL6(cylinder 6) Pressure value of cylinder 6
g.1
g.2
g.3
chemicals should be frequently treated with anti-corrosion treatment such as rust removal.
6.1.3. Comply with the safe operating procedures and DO NOT overload the equipment.
6.2. STORAGE
6.2.1. When not in use, please store the product in a dry childproof place. DO NOT store the product in hot, humid, or non-ventilated places.
7. END OF LIFE
7.1. Through years of normal wear, the digital compression test kit will eventually become unserviceable. When this happens ensure that it
is disposed of in accordance with local authority regulations.
7.2. BATTERY DISPOSAL
7.3. Exposure to high temperatures can cause the batteries to explode; DO NOT dispose of in a re. Some countries have regulations
concerning battery disposal. Follow all applicable regulations. Return used batteries to a collection location for recycling.
VS956 Issue 2 11/03/25
Original Language Version
© Jack Sealey Limited
Sealey Group, Kempson Way, Suffolk Business Park, Bury St Edmunds, Suffolk. IP32 7AR
01284 757500 sales@sealey.co.uk www.sealey.co.uk
Note: It is our policy to continually improve products and as such we reserve the right to alter data, specifications and component parts without prior
notice.
Important: No Liability is accepted for incorrect use of this product.
Warranty: Guarantee is 12 months from purchase date, proof of which is required for any claim.
WEEE REGULATIONS
Dispose of this product at the end of its working life in compliance with the EU Directive on Waste Electrical and Electronic Equipment
(WEEE). When the product is no longer required, it must be disposed of in an environmentally protective way. Contact your local solid
waste authority for recycling information.
BATTERY REMOVAL
Under the Waste Batteries and Accumulators Regulations 2009, Jack Sealey Ltd are required to inform potential purchasers of products
containing batteries (as defined within these regulations), that they are registered with Valpak’s registered compliance scheme. Jack
Sealey Ltd’s Batteries Producer Registration Number (BPRN) is BPRN00705.
ENVIRONMENT PROTECTION
Recycle unwanted materials instead of disposing of them as waste. All tools, accessories and packaging should be sorted,
taken to a recycling centre and disposed of in a manner which is compatible with the environment. When the product
becomes completely unserviceable and requires disposal, drain any fluids (if applicable) into approved containers and
dispose of the product and fluids according to local regulations.
REGISTER YOUR
PURCHASE HERE
