1993 BMW 318 no compression in any of the cylinders?

Those readings are taken by just a compression gauge? If it was me I'll reconfirm it with a cylinder leakage test.

Compression gauge readings:. Low compression in all cylinders would tell you the rings and cylinders are worn and the engine needs to be overhauled.

Cylinder leakage tester readings: A cylinder that has poor compression but minimal leakage usually has a valvetrain problem such as a worn cam lobe, broken valve spring, collapsed lifter, bent push rod, etc.

If all the cylinders have low compression but show minimal leakage, the most likely cause is incorrect valve timing. The timing belt or chain may be off a notch or two.

If compression is good and leakage is minimal, but a cylinder is misfiring or shows up weak in a power balance test, it indicates a fuel delivery (bad injector) or ignition problem (fouled spark plug or bad plug wire).

Labor hours depends on what's really wrong-