Craftsman mower won't start. Cleaned carb. What else to check?

[ilyaz]

This plastic part, which the rubber o ring fits over, was cracked/broken all the way around so that it came away in two parts when I replaced it.

Thank you much for all the details! Since it cracked, I would expect it to leak fuel -- was it?

 

[Fish]

Take off your air filter and look into the throat, and then press the primer bulb firmly several times. You should see a pulse of fuel splash up with every button press. The gasket between the air filter base needs to be perfect for this operation to succeed, sometime beefed up with a little smear of sealant on the gasket sides.
If you see the fuel pulse up, and still no start, then your problems are elsewhere.

 

[seattlepioneer]

Thank you much for all the details! Since it cracked, I would expect it to leak fuel -- was it?

No. This part was the intake manifold that conducted fuel/air mixture from the carburetor to the engine valve.

Because it was broken/cracked, the vacuum developed by the piston sucked in air from the crack rather than atomized fuel/air mixture from the exit of the carburetor.

So---- no leak, but no fuel/air mixture for the engine to burn either!

Hope that enables you to visualize what was happening. And one other thing to check when the engine wont start.

 

[ilyaz]

Take off your air filter and look into the throat, and then press the primer bulb firmly several times. You should see a pulse of fuel splash up with every button press. The gasket between the air filter base needs to be perfect for this operation to succeed, sometime beefed up with a little smear of sealant on the gasket sides.
If you see the fuel pulse up, and still no start, then your problems are elsewhere.

Trying to figure out where precisely I should be looking. Pressed the bulb but heard/saw nothing. I took a few photos -- anything there seems out of whack?

(In the 1st photo I took off the plate, then put it back on)

 

[ilyaz]

No. This part was the intake manifold that conducted fuel/air mixture from the carburetor to the engine valve.

Because it was broken/cracked, the vacuum developed by the piston sucked in air from the crack rather than atomized fuel/air mixture from the exit of the carburetor.

So---- no leak, but no fuel/air mixture for the engine to burn either!

Hope that enables you to visualize what was happening. And one other thing to check when the engine wont start.

That'll be my next thing to try.

 

[Scrubcadet10]

I think you have the wrong carb, you shouldn't have a Choke and a primer....
I don't think the primer will function on a choke style carb.

 

[ilyaz]

I think you have the wrong carb, you shouldn't have a Choke and a primer....
I don't think the primer will function on a choke style carb.

Are you saying you can install a wrong-type carb and it will fit?

FWIW, the mower did run when the previous owner gave it to me. He said he had to occasionally take of the air filter and spray carb cleaner(?) to be able to start it.

 

[Scrubcadet10]

Yes, there were 3 types for that series of engine, one with a choke, or a auto choke, and one with a primer. and I've never seen one of those engines from the factory with a choke and primer. Was there a cable or anything hooked up to that choke valve on top of the carb? the correct part number you need for the primer system is 799868

PartsTree - Home of OEM Parts for Outdoor Power Equipment

Parts lookup and repair parts diagrams for outdoor equipment like Toro mowers, Cub Cadet tractors, Husqvarna chainsaws, Echo trimmers, Briggs engines, etc.

www.partstree.com

 

[Scrubcadet10]

Choke carb is on the left, primer carb on right... on the primer carb you can see a small hole drilled below the top left bolt hole, that's where the air gets pushed into from the primer. Your choked carburetor doesn;t have that, so it will not prime.

 

[Fish]

Put a piece of tape on the top that will hold the choke closed, and then try to start. It probably will.
But once it does, it will run very rich, unless you pull the tape off quickly.