Sears ZTS 7000 B&S 21hp leaking & burning oil

12 years ago

A few weeks ago, I was mowing winter weeds & picking up leaves with my Craftsman ZTS 7000 (Briggs & Stratton 21hp Platinum Series) and noticed a little blueish smoke. After about 15 minutes of mowing it let out a big puff of blue smoke. I immediately headed to the garage to check it out. I noticed oil on the deck under the carburetor and it appeared to be coming from the fuel pump. I called Sears service and scheduled an appointment.

Fast forward 2 weeks and the Sears service tech showed up. We discussed the problem and he diagnosed it as a sticking needle in the carb, causing gas to flood the crank case, causing oil to be forced into the combustion system. He replaced the carb and fired it up. Unfortunately, it's pouring rain, so he let it run on the carport for a few minutes and called it fixed.

A week later it dried out enough for me to get back to mowing and within 10 minutes it sputters and let out a HUGE cloud of blue smoke. I parked it and there's oil dripping from from a hole on the fuel pump again.

In conversation, while replacing the carb, the tech mentioned that sometimes on a sloping yard like mine, the mower will "vent" oil from the crank case into the combustion system when the carb is on the downhill side of the slope. I take it back out on the yard and test it. Sure enough, on even a slight slope, it smokes. On a bigger slope, it sputters and fogs the neighborhood. During my short test run, the oil level went from full to about 1/8" below the add mark. We're talking maybe 10 minutes of total run time.

I bought the mower mid season last year, mowed the yard every week and used it to bag leaves all winter on my sloping yard with absolutely no signs of oil use or smoke.

Sears is scheduled to come back out next week, and I wondered if anybody here has any theories in case he can't figure it out and tries to tell me it's just the crank case vent. Why would that have just started & what can I do about it? I've got a 1 1/2 years left on the warranty & need to figure this out. Obviously, I can't smoke out the neighborhood on every mow.

Sort by:Oldest

Comments (6)

rcmoser
12 years ago
oil level not over filled? (if gas filled the crank case this over filled condition could of causes down stream problems (blown head gasket???) IMO if it didn't do it last year it should not be doing it now. Probably head gasket, cracked head or even ring problem.I would keep calling and complaining till they Change the engine while it's still under warranty. It should not be using that much oil in 10 min. Even on slight or steep slop, IMO it will just get worse. Usually with fuel pump anti-sihpon problems are minimal due to the fuel pump higher than the gas tank. If the gas tank is higher than the carb. most recommend fuel cut-off valve placed before the fuel pump to cut any static fuel pressure that may work it way pass the fuel pump and carb. Your fuel pump has diaphram thats vacuum controlled off the cylinder head.
caulk_king
Original Author
12 years ago
Thanks for your reply rcmoser. I don't think the oil was ever overfilled by the gas. I never smelled gas in the oil or saw a change in oil viscosity. I considered the head gasket, but wouldn't it leak regardless of engine angle?
Related Professionals
Simpsonville Landscape Architects & Landscape Designers · Bellflower Landscape Architects & Landscape Designers · Waterbury Landscape Contractors · Chelmsford Landscape Contractors · El Segundo Landscape Contractors · Fort Wayne Landscape Contractors · Mequon Landscape Contractors · Siloam Springs Landscape Contractors · Tehachapi Landscape Contractors · Tustin Landscape Contractors · Hueytown Landscape Contractors · Auburn Window Contractors · Jacksonville Window Contractors · Oviedo Window Contractors · Wilmette Window Contractors
mownie
12 years ago
I did not read where you had changed the crankcase oil after the new carb was put on.
If the old carb had been leaking there would certainly have been a quantity of gasoline in the crankcase oil.
What happens is that when the engine is started with gasoline in the crankcase oil, after the engine begins to get warm........the gasoline begins to boil out of the oil.
The evaporated gasoline then vents out through the intake manifold carrying a mist of oil with it. This oil laden mist is then burned in the combustion chamber.
This scenario has been repeated countless times.
If ever your engine gets gas into the oil this will occur.
In addition to the new carb did the "tech" suggest that you need to install an inline fuel cut off valve and shut the valve off except when you are actually using the machine?
Having an inline cut off valve and using it consistently is the ONLY way to ensure you never have this issue again.
Even after you change the oil (and filter if equipped) you can expect some smoke for a few minutes until all the residual oil is burned out of the exhaust system.
caulk_king
Original Author
12 years ago
@mownie7 - No, the tech never mentioned that I needed to do anything. No oil change, no nuthin'. I still don't smell gas in the oil.
mownie
12 years ago
From your opening statement.
***"Sears service tech showed up. We discussed the problem and he diagnosed it as a sticking needle in the carb, causing gas to flood the crank case, causing oil to be forced into the combustion system."***
Causing gas to flood the crankcase.
The crankcase is where the engine lube oil resides.
The carb might not be leaking additional fuel now.........but the fuel that was already present will continue to result in smoking exhaust until it is all gone.
Just go ahead and change the oil and oil filter, then operate it normally for about 20 minutes to see if the smoking persists.
If the heavy smoking persists, then your head gasket may indeed be at fault.
caulk_king
Original Author
12 years ago
Update: The sears service tech came out today & test drove/ mowed for about 15 minutes. Not only did it smoke & drip oil from the fuel pump, but it began stalling, dying, & blowing oil from the dip stick. He theorized that it was either a blown head gasket or a broken ring. Either way, thanks to the warranty, he'll be installing a new engine in a two weeks.