Engine Compression

Deactivate fuel injection system by removing fuel pump relay before performing compression test. On 3 series vehicles, fuel pump relay is on bracket on left front shock tower (center relay on bracket). On 5 and 7 series vehicles, fuel pump relay is in relay box in right rear corner of engine compartment. On 635CSi vehicles, fuel pump relay is on left side of engine compartment, attached to outside of relay/fuse box.
NOTE: See L - WIRING DIAGRAMS to help identify relays.
Ensure battery is fully charged. Check compression with engine at normal operating temperature, throttle fully open, and engine at cranking speed.

COMPRESSION SPECIFICATIONS