Check compression pressure - AR01.00-P-1200CD

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ENGINES 651 in MODELS 166, 172, 204, 207, 212, 218, 221

Fig 1: Checking Compression Pressure

Courtesy of MERCEDES-BENZ USA

	Remove/install
	Risk of injury to skin and eyes caused by handling hot or glowing objects.	Wear safety gloves, protective clothing and safety glasses, if necessary.	AS00.00-Z-0002-01A
	Risk of explosion caused by fuel igniting. Risk of injury to skin and eyes caused by fuel spraying out at high pressure	Keep all ignition sources out of hazard area. Do not carry out any work on system when it is pressurized.	AS07.16-Z-0001-01A
1	Bring engine to operating temperature (approx. 80°C)	Only check compression pressure when engine is at normal operating temperature.
2	Switch off ignition	On vehicles with code (889) Keyless Go, press Start-Stop button repeatedly until the ignition is switched off.
3	Open engine hood	MODEL 166.0	AR88.40-P-1000GQ
		Model 172.4	AR88.40-P-1000V
		Model 204.3, 207, 212 Model 218, 221	AR88.40-P-1000EW
4	Remove cylinder head cover trim	Model 204, 207 Model 166, 172, 218, 212, 221	AR01.20-P-5014-02CD
5	Remove fuel filter	Lay fuel filter with attached lines to one side.
		Model 204	AP47.20-P-0780CWD
		Model 166, 172, 207, 212, 218	AP47.20-P-0780EWD
		Model 221	AP47.20-P-0780SXI
6	Remove ceramic glow plugs		AR15.20-P-4111CD
7	Crank engine with starter	Do not crank engine using the transmitter key in electronic ignition lock but use contact switch for compression recorder (1). Crank engine several times to eliminate combustion residues in the cylinder.
		Models 166, 172, 204, 207, 212, 218	AR01.10-P-0110CW
		Model 221	AR01.10-P-0110SX
8	Screw in screw-in fitting (3) with check valve installed in glow plug bore of cylinder to be tested.	Screw-in fitting	Fig 4
9	Connect compression recorder (1) with flexible connecting piece (2) to the screw-in fitting (3).	Compression recorder	Fig 2
		Intermediate piece	Fig 3
		Screw-in fitting	Fig 4
	Checking
10	Check compression pressure	To do this, crank engine with starter for at least eight revolutions. Do not crank engine using the transmitter key in electronic ignition lock but use contact switch for compression recorder (1).
10	Check compression pressure	Compression recorder	Fig 2
11	Carry out test procedure at remaining cylinders in the same way
12	Compare pressure readings obtained with specified pressures	Compression pressure: installation tolerance or new value	*BE01.00-P-1001-01A
		Compression pressure: permissible difference between individual cylinders If the pressure lies below the minimum compression pressure or if the permissible difference between the individual cylinders is exceeded, also check for cylinder leakage. See ↓	*BE01.00-P-1003-01A
		Check cylinders for leaks	AR01.00-P-1300CD
13	Install in the reverse order
	Risk of accident caused by vehicle starting off by itself when engine is running. Risk of injury caused by contusions and burns during starting procedure or when working near the engine as it is running	Secure vehicle to prevent it from moving by itself. Wear closed and snug-fitting work clothes. Do not touch hot or rotating parts.	AS00.00-Z-0005-01A
14	Check fuel system for leaks with engine running		AS00.00-Z-0005-01A

COMPRESSION PRESSURE

Number	Designation		Engine 651
BE01.00-P-1001-01A	Compression pressure: installation tolerance or new value	bar	23 to 30
BE01.00-P-1003-01A	Compression pressure: permissible difference between individual cylinders	bar	≤ 3

Fig 2: Identifying Compression Tester (001 589 76 21 00)

Courtesy of MERCEDES-BENZ USA

Fig 3: Identifying Intermediate Piece (611 589 02 63 00)

Courtesy of MERCEDES-BENZ USA

Fig 4: Identifying Screw-In Fitting (640 589 00 63 00)

Courtesy of MERCEDES-BENZ USA