snow blower does not like running for more than 10-15 minutes

[Vikas]

I can feel it losing power after 10-15 minutes. The problem becomes obvious if I put it on the slow idle and just park it. The engine eventually dies after very slowly losing the speed. It is Craftsman 9hp Tecumseh engine. Just before dying if I push primer, the engine gets reprieve until it starts dying again.

The obvious answer is "go clean the carburetor" but I am trying to find if there are any non-invasive "dump miracle chemical" in the tank procedures.

It had been working pretty well after I had removed the bowl nut and cleaned and squirted the carb from below before the start of the season. Of course, I only did that because it was not starting at that time! This particular problem of losing power after 10-15 minutes has plagued this blower for last couple of years and I thought I had nailed it but now it is back again. I suppose there are dirt or some disintegrating parts in the fuel system causing the problem.

Do I have any choice but to at least remove the bowl nut again and clean all the orifices on it? I don't really want to do it if it can be avoided but Gumout and/or Berryman has not helped. On the contrary I wonder if it is making it worse by causing more disintegration inside.

 

[WobblyElvis]

Check the fasteners on the intake and the head bolts. Make sure they are tight.

 

[KGMtech]

I would start with inspection of the fuel line, it might have debris clogging the flow of fuel. That it works when you pressurize the line with the primer bulb supports that the line is not allowing the normal flow of fuel.

 

[Vikas]

Originally Posted by WobblyElvis
Check the fasteners on the intake and the head bolts. Make sure they are tight.

Can you explain your reasoning? Won't it get progressively worse aka fasteners would have fallen out by this time? The electric start motor bolts *did* fall out on this blower.

 

[Trav]

Check the carb vent.

 

[Donald]

Unscrew the gas cap immediately when it stops. Hear anything?

 

[c502cid]

Not going to help with anything resembling diagnosis, but I have a lawnmower I got free off Craigslist. Original owner said it quit running. Had half a tank of fuel when I got it. Filled it up and it fired right up. Dies when it hits half a tank. Fill it up, runs fine again....

 

[Whimsey]

Try running it with the gas cap loose so it can vent and see if it runs and doesn't quit after 10-15 minutes like it does now.

Whimsey

 

[EdwardC]

Originally Posted by Donald
Unscrew the gas cap immediately when it stops. Hear anything?



This was my guess too, see if the fuel was getting stopped up. Did you check for spark when it wasn't running? Maybe a hot coil issue?

 

[Vikas]

Originally Posted by Trav
Check the carb vent.

Is there a separate carb vent? I thought it was gas cap that was vented.

 

[emmett442]

These engines have a reputation for the exhaust valve receding as the engine ages. That eliminates the appropriate valve lash. Then, once the engine gets hot and everything expands slightly, the exhaust valve doesn't quite close until it cools back down.

Pull the breather cover off and check valve clearance or check compression when it starts acting up.

 

[Trav]

Most do, a clogged cap vent hole will prevent fuel from reaching the bowl but so will a clogged carb vent which is usually very small and easy to clog. An example I have no idea what carb you have. It will be very small and hard to see.

Red= Vent hole
Green= Fuel inlet
Yellow=Idle adjust
PurpleBlue

 

[javacontour]

Carb freezing?

 

[Vikas]

what does the primer bulb do? it only adds extra air, right? the engine speed goes up because extra air must cause extra fuel to get in too; is that coming from main jet then?

does that not imply that carburetor is able to supply extra fuel when asked for? does that still square off with clogged vent theory?

 

[CharBaby]

Check/change the spark plug. It may have a hairline crack in the insulator that causes the engine to quit after that 10-15 minutes. The engine may start & run fine at first but then quits afterward.

Just a thought as this has happened to me and you can't see the crack or tracking...sometimes!

 

[Trav]

It just draws fuel into the bowl but a clogged vent in either the cap or the carb can prevent it from free flowing into the bowl once its running. Some bulbs force fuel in place of a choke like in some lawnmowers with not throttle or choke levers.
Its just something to check, it can also be something electrical, make sure it still has spark when it does this, you can also give it huff of starting fluid and see if it keeps running.

 

[Dave9]

I vote gas cap since the primer bulb helps. You're probably drawing a vacuum in the tank because the gas cap one-way vent has become ineffective. Thanks EPA!

 

[irad]

I have same snowblower. If it is not the carb/gas cap, all above suggestions were good, I just added gear oil to the gear case at the point where the power/impeller shaft turns the auger shaft. It is the top front bolt on the gear housing.

 

[StevieC]

Check gas cap by leaving it really loose, check the vent on the carb.

 

[Vikas]

It does not die like an electrical fault would do. It definitely seems to slowly runs out of enough fuel to keep it running and the lack of vent would be the most probable cause.

Can those gas cap be cleaned or I will need a new one? I guess I could drill a tiny hole in it?