Gas engine dies when hot, but will keep running with choke pulled out a little bit

ericm979 · Jul 14, 2017

Restricted airflow would cause it to run rich, not lean as he's experiencing.

Cedarsnapp, there's a couple ways in theory to check the float level. One is by disassembing the carb and measuring, the other is by using a hose attached to the float bowl to show the level outside the carb. I say in theory because different carb designs often make one of those easier than the other.

But like I said, low float level affects running all the time, not only after 10 minutes. So it's unlikely to be the problem.

The problem started after you changed the fuel filter and flushed the tank. Occam's Razor says that those are probably the causes of the problem. The filter may not be flowing fuel fast enough to keep the float bowl full. Or the tank flushing may have gotten gunk into the inlet.

You can measure flow by removing the feed to the carn and running it into a container. Turn on the gas tap or unblock the fuel line if there's no tap and measure the amount of flow in a minute. Your shop manual may have a spec for that but if it doesn't you can still see if its a good flow or a trickle.

Spanner · Jul 14, 2017

Cedarsnapp said:
Spanner,

Thanks for your thoughts. I know what and where the float bowl is, but I don't know how to check it. Would it fill up again by gravity once I turn off the engine? Do I just quickly remove it or is there a better way to check the level? Thanks.

I would think (without looking) that YouTube has videos showing this procedure. It has just about everything else for these tractors.
I'm also wondering about air-leaks downstream of the carburetor. Maybe at the inlet manifold? Adding choke would help compensate for air-leaks.

RSKY: The engine is apparently running lean and adding choke keeps it running. A blocked air filter is causing the mixture to be rich, not lean.

(Edit: Posted from P.1 and just seen Erics post above. Similar thinking.)
:wrench:

Spanner · Jul 14, 2017

Some good advice options in this earlier thread:

http://www.tractorbynet.com/forums/massey-ferguson-owning-operating/358097-mf-135-gas-wont-stay.html

:wrench:

s219 · Jul 14, 2017

An old timer's trick when your tractor is sputtering as it runs out of gas is to flip the choke on. I used to do that with my riding mower when it was out of gas, and it would buy me enough run time to make it the 400' back to the barn. I'd be inclined to think this is a fuel delivery / fuel starvation problem first, and then maybe think about conditions that could cause lean running second. Seems to me that if it started after you changed the fuel filter and cap, then one of those is at fault. Poor venting through the cap could cause fuel starvation. Wrong filter or filter with a lot of restriction could cause fuel starvation.

Tractorable · Jul 14, 2017

My FJ40 Land Cruiser had a similar problem. It would start and idle just fine but when I went to drive it it would stall and die after going about 100yds. I eventually put a vacuum pump on the fuel line and discovered I could barely suck any fuel through. It got enough fuel to idle but that's it.

Turned out the hard line going into the fuel tank was 90% clogged with weld when a previous owner welded the hard line to the fuel tank flange.

Run your fuel line to a separate fuel container to check for fuel starvation upstream of the carb. Once you eliminate that as a potential issue then move your focus to the carb.

Cedarsnapp · Jul 17, 2017

UPDATE: PROBLEM SOLVED. Thanks so much to everyone for excellent suggestions. I checked the fuel flow after the filter (excellent) and after the line from the fuel filter to the carb (also excellent). I checked all the hoses and carb connections, tightened them and found one hose connection from air cleaner to carb was slightly loose, probably allowing some air to leak. That seemed to help a bit but problem still lingered. Then I cleaned the inside of the carb (squirted some Gumout Carb cleaner down air intake while engine was running and that cleared it up. Now runs great. So probably was partial clog in a carb jet. Carb is a Marvel - Schebler and appears to be very basic.