Compression Test
AllData Editors Note - Ford does not provide a cranking pressure specification, only an acceptable range.General Remarks
NOTE: Removing fuses and disconnecting electrical components causes the powertrain control module (PCM) to show an error message. After measurement has been carried out this error message should be cleared from memory by connecting scan tool.
NOTE: Only check the compression pressure with the valves set to the prescribed clearance (if this can be adjusted).
Check the compression pressure with the engine at operating temperature.
Differing designs of compressor pressure recorder and varying starter motor speeds usually only make it possible to check that the compression is the same in all cylinders.
Check the Compression Pressure
Differing designs of compressor pressure recorder and varying starter motor speeds usually only make it possible to check that the compression is the same in all cylinders.
Check the Compression Pressure (2.0L SPI Engine)
WARNING: On manual transaxles shift the transaxle into neutral. On automatic transaxles select "P". Failure to follow these instructions may result in personal injury.
1. Open the central junction box (CJB) and remove the fuel pump relay.
2. Start the engine: the engine will start up, run for a few seconds and then stall.
NOTE: Turn the spark plug connectors slightly before pulling them off. Pull on the connector, not on the cable.
3. Pull off the spark plug connectors.
4. Pull off the ignition coil connector.
5. Remove the spark plugs and keep track of spark plug location for installation.
NOTE: Operate the starter motor with wide open throttle until the pointer on the measuring device stops rising.
6. Carry out the measurement in accordance with the instructions supplied with the measuring device on every cylinder using Special Tool 1 64-R0253.
NOTE: Coat the spark plug connector gasket with silicone grease (A960-M1C-AA) before installing.
7. Install the components in reverse order, keeping to the specified tightening torques: coat the spark plug thread with spark plug lubricant. Tightening torque for spark plugs: 15 Nm. The spark plugs must be installed in their original cylinder locations.
8. Repeat the test on each cylinder.
9. Reset the PCM fault memory.
Check the Compression Pressure (2.0L Zetec-E Engine)
WARNING: On manual transaxles shift the transaxle into neutral. On automatic transaxles select "P". Failure to follow these instructions may result in personal injury.
1. Open the central junction box (CJB) and remove the fuel pump relay.
Start the engine: the engine will start up, run for a few seconds and then stall.
NOTE: Turn the spark plug connectors slightly before pulling them off. Pull on the connector, not on the cable.
2. Pull off the spark plug connectors and remove the spark plugs.
3. Pull off the ignition coil connector.
NOTE: Operate the starter motor with wide open throttle until the pointer on the measuring device stops rising.
4. Using Special Tool 164-R0253 carry out the measurement on every cylinder.
NOTE: Coat the spark plug connector gasket with silicone grease (A960-M1C-M) before installing it.
5. Installing the components in reverse order, keeping to the specified tightening torques: coat the spark plug thread with spark plug lubricant. Cylinder head cover tightening torque: Stage 1: 2 Nm,. Stage 2: 7 Nm. Spark plug tightening torque: 15 Nm.
6. Reset the PCM fault memory.
Interpretation of the Results
The indicated compression pressure are considered within specification if the lowest reading cylinder is within 75% of the highest reading.
CAUTION: If engine oil is sprayed into the combustion chamber, after carrying out the measurement run the engine at 2000 rpm for about 15 minutes, in order to burn the oil and prevent damage to the catalytic converter.
If the measurement on one or more cylinders is much lower than the specified value, spray some engine oil into the combustion chamber and repeat the compression measurement.
If the reading greatly improves then the piston rings are damaged.
If the reading stays the same then the cause is either bad valve seats or valve stem oil seals.
If the measurements for two cylinders next to each other are both too low then it is very likely that the cylinder head gasket between them is burnt through. This can also be recognized by traces of engine oil in the coolant in the engine oil.