Timecutter Z420 runs fine for 8 minutes then starves for gas. Does this continually

[rickharp]

B&S engine. before and after the Tune-up kit and oil change, the mower would run and cut fine for about 20 minutes, then for no reason experience an immediate starving for gas, like it got air in the line or running out of gas. i could shut the blades off and idle it for 40 seconds, then rengage and rev up, and cut for anohter 6-8 minutes.
First thought it had somethign to do with riding on a hill, then thought it was the trigger for the safety seat.
I did change the gas filter and air filter.
could it be a gas line air leak. there is no leaking gas. fuel is full. mower is a 2005 with light useage.
starts up fine, runs as good as it did when it was new. outside temp: 75F. Grass not that high. Load or no load would starve but never shut down.
Any thoughts or other threads you can think of. Thanks

btw, for the past 4 years or less, when we turn it off after cutting the yard, we get one really loud backfire. a work around to prevent this is to shut it down with throttle still on pretty high. so maybe its the fuel shutoff solonoid. if it is, how can i check this or make sure it is the "fault".

i will try the fuel cap idea i read about. since it runs initially at 20 minutes, then the gaps are at 8 minutes.

 

[Rivets]

Two things I would check. First, do you have a clear fuel filter to see if you are running low on fuel? If it is running low, it might be the fuel pump. See if you can see the filter getting fuller while you are idling, wait to reengage the blades. If the fuel solenoid is bad the engine would normally shut down very quickly. It could also be a crack pulse line to the fuel pump which would make the pump look bad.

 

[rickharp]

Thanks for the reply.
I have the typical pancake filter (Briggs and Stratton394358S (replaces 394358)
FILTER-FUEL). and I can't really see through the white plastic.
i dropped the fuel solonoid just to look at it. seemed ok.
someone said i could cut the wire or plunger portion of the solonoid as it wasn't doing much. is that an option?

here is an update to the circumstance, which is very consistent from a cool engine:
runs and cuts 100% fine for about 15 minutes, then for no reason, coughs and rapidly goes into a almost shutdown. most of the time i can salvage it quiting by disengaging the blades and bringing the throttle down. I can leave it running idle for about 2 minutes and throttle back up and start cutting again, works good for 6-8 minutes this time, will do same cool down and again, same 6-8 minute stall or cough... i do this till the lawn is done.

I have played with the gas cap and even partially opened it with same results. Not sure but seems to be a hot engine issue or a gas issue. weather has been in the mid 70's. load is not too much. Still hopeing for some more opinions. Thanks so much.

 

[Rivets]

Sorry I have not gotten back to you, had something's that needed attention. Two things I would try. Install a clean inline fuel filter. This way you will be able to see if you are getting fuel to the carb. Kohler makes two, get the smaller one. If you are not getter fuel you probably have a fuel pump issue. There I would check to see if I would have a cracked pulse line which opens when hot. Finally DONOT CUT THE FUEL SOLENOID WIRE. This would kill the engine.

 

[rickharp]

Thanks so much Rivets for checking in with me. I am still trying to figure this out.
in your reply, I am pretty sure my Z4200 from 2005 does not have a fuel pump. a valve sits under the tank and it appears to be gravity fed to carb. Could that be the case, and if so, then your pulse line comment would not be a concern.
i am going to install new fuel lines, and a new filter that i can see through, and see if that changes anything. next i'll rig up a IV like they have in the hospital and run with that for 20 minutes to see if it happens with a secondary source.
keep thinking about that 15 minute and 8 minute cycles. Thanks

 

[Rivets]

Please give me the model, type and code numbers on the engine.

 

[rickharp]

i replaced the new fuel filter with another pancake one that is clear so i can monitor the flow and look for air. I also disconnected the fuel line from the carburator and noticed a very slow flow, so i blew forced air into the line and at that point experienced a much better flow from the tubing. perhaps there was some sort of buildup in the line. will cut the grass today to see if that fixed it. i feel confident it made a difference.

I wonder, if the 2005 models, no fuel tank pump, that Toro introduced the pump in later models because it may of had some issues with gravity feeding. hmmm. Let's see. thanks

update: I just finished cutting the grass with no stalls. Very happy. feel it was more the fuel line blockage than the filter or a leak in the fuel line. Thanks to all.

 

[Pete.S]

If changing the little pancake fuel filter helped I suggest that you go to your NAPA or other store and buy a larger fuel filter with a see through bowl. Bring along the pan cake filter so you can match up the fuel line size on the filter to what you need. I would also suggest that when you run your tank to nearly MT take it off, safely drain off the remaining gas and then clean the snot out of the tank. Make sure there's no water left in the tank when you reinstall it.