F935 cranks but won't start, has run perfect

[pclose]

Ok I checked the compression. The gauge isn't great, but it had a touch under 300 psi in #1 and #3. That's low, but engine's cold and it's 34 years old. The thing is it only had 160 psi in cylinder 2. I put a teaspoon of oil into the glowplug hole of #2 and the compression went to 300+ when i tested again. I didn't bother doing #1 & #3 over. Test results indicate a ring problem when compression goes up after adding the oil right? Cranking it for the #2 wet test I noticed the air was coming out the exhaust again instead of the blowby. If cylinder #2 is shot I'll know what I have to do, but it is still strange to me that I had no real problems starting and running the engine prior to the no-start, 15 minutes after running it.

Thanks for all the advice and info. I appreciate it

 

[Kyle_in_Tex]

Ok I checked the compression. The gauge isn't great, but it had a touch under 300 psi in #1 and #3. That's low, but engine's cold and it's 34 years old. The thing is it only had 160 psi in cylinder 2. I put a teaspoon of oil into the glowplug hole of #2 and the compression went to 300+ when i tested again. I didn't bother doing #1 & #3 over. Test results indicate a ring problem when compression goes up after adding the oil right? Cranking it for the #2 wet test I noticed the air was coming out the exhaust again instead of the blowby. If cylinder #2 is shot I'll know what I have to do, but it is still strange to me that I had no real problems starting and running the engine prior to the no-start, 15 minutes after running it.

Thanks for all the advice and info. I appreciate it

The smoke you first talked about had me thinking low compression or ring failure. So the odd smoke was your tattler.

Sorry that it went downhill. Keep us posted about what you want to do.

 

[TractorGuy]

I don't think a little under 300 should be a concern on an old cold engine. The dry wet test on #2 does indicate a ring problem but i find it hard to believe it would prevent the engine from starting with 2 good cylinders.

Have you checked resistance on the glow plugs? I don't know the value you should look for but if they are open or shorted you could be pretty sure they are bad.

I came across this video showing how to test the control relay. Apparently it activates the light for about 8 seconds but the glow plugs should get power for 30 seconds. Just connecting a volt meter or test light to the glow plugs would be a simple way to test that but this guy shows how to bench test the relay.

YouTube

 

[pclose]

Thanks again for all the help. After some additional sleuthing I think I know what happened. I got this mower free a few years ago when the previous owner needed it gone. It needed a lot to get going, but I wasnt aware of it's history, or what was correct vs wrong. One of the things I now realize is very wrong is the washer and wing nut that he'd been using to keep the air filter attached in the filter housing. Upon further review the hole in the washer creates open gaps on either side. Direct access for outside air through the intake and right into the center cylinder where I have minimal compression. I'm going to get some new glow plugs, triple check fuel delivery, add the teaspoon of oil that got me compression and try and start it. I'm of the opinion that I can get it to run. If it does I'll cut my grass. Either way I will look into fixing it. I'll talk to a machine shop and shop rebuild kits and see if it's something I should do. I'll let you know if it starts.

 

[TractorGuy]

An F935 for free was a pretty good deal. I have lucked into a few free mowers but nothing like that.

I paid a grand for my F725 and it was a project mower with a spare for parts. The catch was I was told it came with a like new deck but didn't see the deck until time to pick it up. The deck wasn't for an F725. I ended up having to modify it to fit. It didn't even have the gearbox mounts. Must have come off a zero turn or some other mower that wasn't shaft driven.