For the Lords of Wisconsin

[NCmau]

While back I have posted a problem on a Wisconsin TJD mounted on a Yazoo mower. Even though I have received great suggestions, the problem is still existing. Here is the problem and the diagnostic history.

First start, the engine runs perfect. After few minutes stops. Starts and runs again for few minutes, then quits again. (I like to point out that when the engine runs, it runs great).

Things I have done:
Right after engine stops, checked spark. GOOD SPARK consistently!!!
Installed carburetor kit and tested with spare carburetor.(Air intake adjusted)
Cleaned fuel lines, fuel filter and bowl.
Checked fuel pump output (.8 oz. in 30 sec.)
Installed new spark plugs and wires.
Installed new coil, points and condenser (last year)
Cleaned air filter and engine cooling fins.
When engine stops, cylinder head temperature is 225 deg. (normal??)
There is NO heat cutoff switch installed.
Oil level is okay.
Checked gas cap vent
Removed head and removed carbon build-up. Valves appear to be in fair shape. Did not see any major burns.
Spark plugs, especially #1 fouls quickly.
Did not see any manifold gasket problem.
Compression is 98 psi on both cylinders

What I also noticed that the engine is starving for gas. When the engine is about to die, I gave a shot of starting fluid and keeps going.
Also, after the engine quits, there is hardly any gas left in the bowl, but the pump out put seems to be adequate. (Fuel lines and filter have checked several times)

What I plan to do now, unless I get advices to the contrary, bite the bullet and order a new set of valves, new fuel pump, head and manifold gasket.

I just have to resolve this problem. (My grass is getting tall). Thanks again.

 

[Jim k]

Did you take the petcock out of the gas tank and clean the inlet screen.

 

[Bob]

GOOD GRIEF, put your wallet away and fix your fuel flow or carburetor problem! (ASSUMING the engine has spark even while stalling.)

You could start by connecting a fuel pressure gauge by "teeing" into the line between the fuel pump and carb and watching the fuel pressure from startup 'til it dies.

If there's less than probably 3 to 5 PSI and/or it drops to nothing as it begins to die, the problem is BEFORE the carburetor. If the fuel pressure holds up, yet the engine dies from lack of fuel, there's something wrong INSIDE the carburetor.

(BTW, any chance there's a clogged screen on the carburetor side of the fuel inlet fitting?)

Actually, it sounds like a failing fuel pump to me.

 

[Loren in MN]

Just a thought- Does this mower have a fuel cut-off selenoid? I've seen this make it hard to start or stop after starting by closing off the fuel at the carb on some engines. Had one that would only run with the choke on all the way.

 

[NCmau]

Thanks Bob for the good tip of measuring fuel pressure. The reading between the pump and the carb was .1 PSI, which is obviously too low (filter is clean). Also, I ran the machine in place and did not stop. So I guess that it was not getting enough gas under load.

Now a question, instead of ordering a mechanical fuel pump, why not an electric pump? And if so what size should I be searching for, 3-5, 4-7? Last year I tried a car electric fuel pump I had, but I guess it was too big. Gas was everywhere. The reason I like to try an electric pump is that the mechanical one I used, lasted only a season, and the electric one is probably cheaper.

Another question. I believe I do have a compound problem. The valves had lots of carbon built-up, especially in the #1 cylinder area. (They were cleaned before I put the head back). The #1 plug gets fouled up quickly, much quicker than #2. Also when I remove the #1 spark plug wire, there no change in the running rhythm, but when I take #2 off, there is a more significant change.
Is this pretty indicative of a valve problem? Spark pugs and wire are new, rings and walls are in excellent condition.

Hope I am not too big of a pain. Just trying to fine tune this problem.
Again, thank you.
.
Maury

 

[Tramway Guy]

This sounds like a problem I had with a Wisconsin engine many years ago, with vapor lock. Caused by (of all things!) the wrong muffler. Exhaust restriction caused overheating of the manifold and the carb would get too hot, the fuel line got too hot. The engine would not run very long before it starved for gas, same symptoms--the gas in the bowl disappeared.
Installed the right muffler and no more problems.

 

[greygoat]

I second JIM K, if it has a fuel shut off valve,
they usually have an intake screen that goes up
into the tank. when they get dirty the engine
starves for fuel. after it sits debris that was
sucked onto the screen, when running, falls off,
a restart resumes the cycle. Try cleaning the
screen/tank. ALSO, a good spark when cold, but
loosing spark when hot is the sign of a failing
magneto coil.

 

[NCmau]

That's excellent food for thought.

 

[lucas boy]

mine has a fuel pump on it and was doing this same thing. i rigged up a gravity flow tank temp and it ran fine. checked for blockages in fuel lines and ended up getting a new fuel pump to fix it.

 

[NCmau]

That's another good idea. I actually have a rig set up in this fashion when I troubleshoot my 8N tractor. I have already ordered a 3-5 PSI electric fuel pump so I am going to this try the new pump. I am sure at this point the pump is one problem. I will keep the board informed.