[99cobra2881]

Compression test won't show blown crank case seals.

Easy crank shaft seal test.

Remove intake tube and exhaust. Cover both openings with duct tape.

Remove fuel pump.

Use a mityvac or similar device to pull a slight vacuum on the engine block through the fuel pump vacuum port.

It should hold a vacuum. Bad crank seals will show themselves through no vacuum being held and you'll be able to hear the air leaking in to the engine block past the seal or seals.

My recently rebuilt 2pg popped a front crank shaft seal and I used this method to diagnose the blown seal. Compression test showed 130psi. So I thought the fuel pump had quit and I used the vacuum pump to check the diaphragm inside the fuel pump. The fuel pump checked good so I knew I was fighting another issue.

I couldn't hear the leak over the sound of the engine cranking but the mityvac showed the leak instantly. New seal is loctited in place and is the cart is running good.