A tricky one: Simplicity Z-turn with a Briggs Vanguard cuts out

I have a 20 hp Vanguard V-Twin (model 358777) attached to a Simplicity Z-turn. I've had it about 8 years. I've had this thing in the shop now twice (to the tune of nearly $500) and still no luck.

Normally, right after it's been worked on at the shop it runs fine, allowing me to mow my 2-3 acre lawn... once or a little more. But then it starts acting up. It will run along fine, then start losing rpm. When I cut off the deck and choke it it will start back up running; it might run for awhile but then with the deck running, it'll cut out again. This last time after it was "fixed" it ran for awhile but now just starts up... then cuts out completely after a couple seconds, choke or no choke.

Here's what I've done:

- Replaced the fuel intake from the gas tank
- Replaced the fuel filter
- Replaced the fuel pump
- Checked that all the lines are clear (and blown back into the tank to make sure there wasn't any clog)
- Cleaned the carburetor (dealer)
- The dealer also cleaned out some valve in the fuel line that had clogged with rust - can't recall the name offhand.
- I also just ran a clear fuel line directly from the tank to the inlet on the fuel pump and started it (with starter fluid) just to make sure gas was running from the tank to the pump.
- Loosened the gas cap to make sure there wasn't a vacuum (it's a pretty new cap).

At this point, I don't know what else to do. Can anyone help? Thanks in advance; I'm about ready to chuck this and just pay someone else to mow my lawn!

 

Welcome to the forum.
If it wasn't for the dealer visits, I would have guessed the gasket for the carb is either leaking or missing.
The previous requirements for choke indicates it's getting too much air. The fact it needs it after running for a while...

I'll have to think this over a bit. Maybe someone else will come up with a possible issue in the mean time.

 

Having to choke can also indicate that it's not getting enough fuel (same as saying too much air). I'm suspecting the carburetor is ingesting some dirt. With the vibration of running it may eventually pass it or it may still be clogged.

Even though you've had the carb cleaned and fule lines & filter replaced you mention something clogging with rust. At the minimum I would shine a flashlight into the fuel tank to look for sediment or rust. You may need to drain the tank and clean it out. The problem with rust and mineral type contaminants (dirt) is that they cannot be dissolved so the normal carburetor soaking to remove varnish is little help.

 

I think I'd be suspecting the "rusty" part... most likely the petcock. If it is letting a minimal amount of fuel flow through, it could be causing problems. It's not getting enough fuel.

 

Just wondering, did they give you an idea as to how they cleaned the carb?
If they didn't remove it to clean, I would look at another shop.

 

I think you're right that I need to clean out the fuel tank. It's not gravity feed, though; do you have a suggestion as to how to do that? Would you suggest removing all the fuel (I do have a hand vacuum pump), then putting a small amount of clean in, then removing that again, etc?

I do believe the mechanic said he removed the carburetor to clean it.

Is it possible that it doesn't have to do with fuel at al, that it's losing spark or something? I thought it must be fuel since chocking it (at least used to) help it keep going... but what do I know?

 

Check all your fuel lines, if they are soft and mushy, replace them. but then again the mechanic should have caught that. The fuel lines may be closing off and stopping fuel flow. JMO