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I have air being forced out of the dipstick tube when I turn the engine by hand. It does the same when I try with the key. It acts like it has too much compression but I made sure valves were adjusted already. I can't check compression with my gauge because it won't spin enough.
Model 31P777 0348E1 040426ZD

your crank case vent could be blocked or not working properly....:smile:

If you are turning the engine with the dipstick out you will get air being forced out of the engine when you turn the engine. It is caused by the piston displacing the air in the crankcase when it move down the cylinder bore. If the valves are adjusted properly then I would say that the compression release on the camshaft is broke and will required pulling the engine and replacing the camshaft.

Currently doing that on the exact model that you have right now in the shop. The flyweight broke and was laying in the sump when the engine oil pan was removed.

Thats what it seems to me too. But that is with the dipstick in. It hisses really loud when you try to crank the engine. Never had one do that before. Way too much compression and being forced out at the weakest point I guess.

How would you rule out everything to verify tearing into the engine. I have fixed those before but that was when I worked at a shop. I would diagnose and then the boss would verify. I guess I am just second guessing myself.

I had a guy tell me it was a bad starter cable. Because the solenoid was testing good and the starter was testing good but the voltage would drop when I connected to cable to the starter. But could that be because the compression is so high that the ignition system is trying too hard?

Could be blown head gasket between the cylinder and push rod cavity. that could also cause the excessive crankcase pressure.

So I definitely need to do a leak down test?

How do y'all do your leakdown test. I know how to do one but I don't have the test kit. Just wondering some of the ways people have come up with.

I agree with IL bad head gasket. To do a cylinder leakage test I high recommend you borrow or get the proper tester.

Hey Rivets just wondering.....not questioning for sure. I want to know how a blown head gasket builds excess pressure. Just trying to learn from this but one would think that would cause less pressure. And since the mower won't run the leakdown test would be my only option right? Because normally I would spray carb cleaner around it while it is running.
Please don't take that has questioning you. I honestly don't know and want to.

A blown head gasket will allow air to escape back into the through the valve cavity crankcase causing the buildup of crankcase pressure. You will also loose compression in the cylinder. The engine will still run but you will have some lose in power. I was a tech instructor for 34 years and understand that questions that seem obvious to me need to be explained. No offense taken.

This engine does not run because there is so much compression it will not turn over fast enough to start.

We understand that, but your original post talked about symptoms that would indicate a blown head gasket. You may be building pressure in the crankcase not allowing it to spin properly. If you look at a parts breakdown you will see that the head gasket seals between the cylinder and the push rod cavity.

So is a leakdown test the only way to determine without the engine running? Or would I be able to tell by simply taking the head off?

I put a head gasket on since no answer on the last post. It spun over a little better. But not enough to not hang up. So I guess it's time for a new cam.