This &%$#* lawn mower

[Sonny812]

I have a Gravely 812 with a 12hp Kholer bought in 1977. It has mowed a lot of yards and over the last 3 or so years has developed an intermittent problem. I can mow at times for 15 minutes, 45 minutes, an hour before the engine will slowly die down. Sometimes if I push the choke on it will keep running eventually clearing up until it repeats the above. More recently it has begun to simply die. When it does this it is not pumping fuel out of the fuel pump line. Because it was so intermittent I have just lived with it but I finally broke down and started to work on it. This is what I have done so far;
1) clean gas tank
2) replace tank fuel turn off valve and filter with an straight through pipe fitting
3) replaced all the fuel line except the steel but I can see through that
4) replaced the fuel pump
5) cleaned the carb where I found grass in the main jet (thought oh yeah gotcha now - wrong)
5) replaced plug, plug wire, points, condenser, and the wire going to them (insulation burned off)
6) replaced coil which had did have an issue
The lawnmower ran great for about 8 hours and then started doing the same thing. I have rechecked all the above and don't see anything wrong. When it sits for a bit it will push fuel about 1 to 1.5 inches out of the fuel pump line if held straight up. I was wondering if it might be vapor locking and was tryijg to figure how to insulate the fuel line to see or if anyone knows of an electric pump that would work. If anyone has any suggestions I sure would appreciate it.
Thanks in advance.

 

[Rivets]

I would check the fuel pump pulse line for cracks or a leak where it attaches to the engine. If it is cracked, when it gets hot it may open up, not providing the pumping Pulse needed to deliver fuel.

 

[taxidermist]

Did you make sure the gas cap is venting?

Rob

 

[taxidermist]

also read this.

Information about Valves, Seats, Guides, Porting, Camshaft and Exhaust Header Pipe

Rob

 

[Ariena]

Did you make sure the gas cap is venting?

Rob

This is really common. Just try running without the cap on and see what happens.

 

[EngineMan]

This is from the Kohler Service Manual that I have, saying about the same as above post.

Engine Starts But Does Not Keep Running

1. Restricted fuel tank cap vent.
2. Dirt or water in the fuel system.
3. Faulty choke or throttle controls.
4. Loose wires or connections that short the kill
terminal of ignition module to ground.
5. Faulty carburetor.
6. Faulty cylinder head gasket.

Engine Runs But Misses

1. Dirt or water in the fuel system.
2. Spark plug lead disconnected.
3. Loose wires or connections that intermittently
short the kill terminal of ignition module to ground.
4. Engine overheated.
5. Faulty ignition module.

 

[motoman]

Car barake lines can deteriorate internally and create "check valves" stopping flow. Also debris can do this . Run soft headed wire through and observe.

 

[Sonny812]

Guys thanks for the suggestions. I think (hands in prayer mode) I got it fixed. For future reference, this thing has a fitting that comes out of the tank and makes a 90* turn. It also has a filter there. The filter looks good and when I put water in the tank and watched it flowed well. I eventually (out of deperation) replaced it with a plumbing fitting with no filter and it has run fine since. I don't know if the suction caused a collapse or not.

 

[largesarge2]

Can you tell me where you found an 812 fuel pump? My has died after 41 years, but I so far cannot find one. Thanks

 

[Fish]

Can you tell me where you found an 812 fuel pump? My has died after 41 years, but I so far cannot find one. Thanks

Easy enough, just give your Kohler spec numbers...