15HP Command (cv15s) Running Rich

[Wazza65]

I have a John Deere LT150 with a 15HP Kohler Command engine (CV15S) that appears to be running rich, and the spark plug has black sooty deposits consistent with a rich mixture. I replaced the unserviceable air filter and fitted a new spark plug.

It has a Walbro carburettor that does not have a fuel solenoid, and the choke Is opening and closing correctly.

I removed and cleaned the carburettor, drained the fuel tank, and filled it with fresh fuel to no effect.

I performed a pressure test on the carburettor in an inverted position, and it successfully maintained 5psi, indicating that the needle and seat are sealed and there are no grooves on the inlet needle.

I removed the carburettor a second time and bent the plastic tab on the Plastic float slightly, as it appeared to be a little high. While I had the carburettor off, I filed off the limiter on the idle speed mixture screw to allow fine-tuning. Adjusting the idle speed mixture screw had some effect but not enough to correct the problem.
A carby kit here in Australia is $74.

It has hydraulic lifters, so there is no valve lash to set.

I had considered that the fuel pump might be supplying too much fuel, but the float should prevent an oversupply if this were the case. I tested the fuel pump pressure at the carburettor, which is putting out 2.9 psi. I was unable to find the specs for this plastic manual pump. A new pump is $181.


Any thoughts?

 

[Bertrrr]

Has this happened all of a sudden or a gradual thing ? Is it smoking Black / blue / white ?

 

[Wazza65]

Has this happened all of a sudden or a gradual thing ? Is it smoking Black / blue / white

Has this happened all of a sudden or a gradual thing ? Is it smoking Black / blue / white ?I

I

t doesn't blow any smoke while it's running.

Has this happened all of a sudden or a gradual thing ? Is it smoking Black / blue / white ?

Thanks for the reply.

The initial problem was it would run for a while and then stop. This was fixed by replacing the coil. It was then that it began to run rich. It sounds to be running rich, and the spark plug echoes this.

It doesn't blow smoke while running, maybe a little when started with the choke on.

I need to know the maximum pressure that the fuel pump can exert.

 

[Bertrrr]

If the needle and seat are holding , it will only allow so much fuel into the bowl, I've used electric fuel pumps on these guys with no problems as to fuel pressure being too high etc.
To my way of thinking only the carb or it's settings would make it run too rich, not sure there are any adjustments on that particular carb some don't have any , think Id run it like this and see if it clears up over time.

 

[Wazza65]

If the needle and seat are holding , it will only allow so much fuel into the bowl, I've used electric fuel pumps on these guys with no problems as to fuel pressure being too high etc.
To my way of thinking only the carb or it's settings would make it run too rich, not sure there are any adjustments on that particular carb some don't have any , think Id run it like this and see if it clears up over time.

Yes, I agree with you.

I have tested the fuel pump pressure, at 2.9 psi, I don't think that would be a problem. So that leaves the carburettor as the likely problem, so I have decided to take a chance on an aftermarket one.

 

[7394]

Might try & run some Seafoam in the gas, & run it thru thoroughly.

 

[Wazza65]

7394:
Might try & run some Seafoam in the gas, & run it thru thoroughly.
We are unable to get Seafoam here in Australia. I do, however, run the fuel stabiliser Sta-Bil in all my equipment.

 

[Tiger Small Engine]

7394:
Might try & run some Seafoam in the gas, & run it thru thoroughly.
We are unable to get Seafoam here in Australia. I do, however, run the fuel stabiliser Sta-Bil in all my equipment.

If you are counting on Seafoam to fix the issue, you might as well piss, and then pull down your pants.