MTD Tractor Starting problem

[lefty]

Model: 13AS699H088

Engine: 331777-1107-B1 Code 080320ZD

Not the first time I've posted on this machine but first time for this problem. I've acquired this machine as my own now. Starts quickly and runs smooth and strong. It came to me after the owner got a new one. Leaked gas into the crank over the winter but never ran like that. I did a carb cleaning and replaced the suspect components. New fuel lines, fuel filter, other filters and oil change. Runs great except occasionally, it won't start. Just cranks and cranks. It can be running great all day and then just won't start. Or, it may not start the first time using it for the day. I estimate it's about 10% of the time. During one of these episodes, I've checked spark and it appears good. Plug is always bone dry though. It will start with a shot of carb cleaner into the airbox. So I know I have a fuel issue but can't figure it out. Like I said, I've replaced all of the components in the fuel system leading up to the carb and when it runs, it runs awesome. I'm at a loss.

I use this as a tractor to tow my trailer so it doesn't run for hours. It runs for about 15 minutes and then sits for about 20. Most of the time, I have no problem but like I said, occasionally, it busts my chops.

Thanks

[bgsengine]

Intermittent fuel-related no-start like that, I'd run it until the problem happens, then I'd first check if the throttle plate in carb is actually opening fully (could be sticking closed, if shutting down at idle) and/or verify if choke plate is closing as it should when choke is applied. another possible ( but maybe a bit unlikely) is afterfire solenoid sticking. .. how's compression when it happens? another Unlikely but still possible, a valve hanging open a little (or valve seat loose?)

[38racing]

It could also be an intermittent power failure to the carb solenoid. I had a bad ignition switch that was causing one of mine to stop and not start at times.

[lefty]

Thank you.

The problem is happening right now so I took the airbox off and inspected the choke and throttle. No sticking and both appear to be working properly. I can hear and feel the after fire solenoid clicking. With the airbox off, I'm able to shine a light down the carb and see that there is fuel being sucked up and even spitting back out. Given those two observations, I can assume that the solenoid is operating properly? It looks like more than enough fuel is present in the venturi during cranking.

So I guess I'm chasing a possible compression issue at this point? I do have a spare solenoid kicking around if trying that is recommended. I was thinking of starting with pulling the valve cover. I've serviced this machine over the past several years so I'd be surprised to find a cylinder problem, more likely valves. Plus, I find it easier to do a leak down with the valve cover off, from an O.C.D. standpoint. It gives me more confidence in having the right stroke. I know that probably sounds ridiculous to more seasoned guys.

[bgsengine]

No, I'd do a leakdown test with valve cover off, too especially on these intek OHV engines - Not because it's easier to tell which stroke engine is on, but to be able to view and check if a head gasket is blown (even a tiny bit) between the bore and lifter galley - which is a very common issue, and even if it is NOT your issue, if it is blown just a little, it is only gonna get worse, and gives you good enough excuse to pull head anyway and go over valves while it is off...

[lefty]

Makes sense.

So the leak down was not too bad on the numbers, but there was a lot of air coming out of the carb. No sound from the dipstick or exhaust that I could hear but a lot of noise and air coming out of the carb. So I'm guessing the head needs to come off to see why. Sounds like a problem with the intake valve. I'm used to hearing a bit out of the crank but not so much out of the carb. I couldn't hear or feel anything coming from the crankcase.

Regarding the head gasket, it was tough to inspect given all the noise coming out of the carb, as well as my other hand was holding a monkey wrench on the pulley. Maybe some soapy water. But I'm guessing it's moot if I'm pulling the head anyway.

[KE4AVB]

Where these head gaskets blow soapy water will not detect it. They usually between the cylinder and the push rod galley which is why always suggest pulling the rocker (valve) cover listen at the push rod galley. If the air sound coming out of the valve galley is louder then the dipstick tube, it usually indicates a blow head gasket on the 210000, 280000, 310000, and 330000 series Ohv engines. Also when installing a new head the final torque is 21 ft-lbs now per Briggs.

[lefty]

The head gasket definitely looked buggered next to the galley.

[38racing]

The head gasket definitely looked buggered next to the galley.

facing the block is my guess.

[KE4AVB]

Usually...