Help!!!...fuel line issue at wits end!!

[pgapro112]

I'm able at my wits end trying to fix my older craftsman lawn tractor and I'm hoping you all can be of assistance. It starts up fine and runs for a while before stalling out (initially runs for quite a while). After trouble shooting several things I've come to believe it's a fuel line issue. I'm using a clear inline fuel filter so I can see what the fuel level there is and how's it's entering/leaving. The tractor runs fine and then slowly the fuel level in the filter drops as it uses fuel until it runs out - it's almost like it's not pulling enough fuel from the tank. Here is all I've done:

1. Replaced the fuel filter (no change)
2. Drained, rinsed, and refilled the fuel tank (no change)
3. I then started piecing everything thing back together to see if there were any clogs, etc. Nothing.
4. Gas tank drains perfectly by itself (good!)
5. When the fuel line from the tank is disconnected from the fuel filter the fuel gushes out and pulls from the tank (good!)
6. When the filter is disconnected from the line going to the carb the fuel gushes out and pulls from the tank (good!)
7. When the line connecting to the carb is disconnected fuel gushes out and pulls from the tank(good!)

As you can see there doesn't appear to be any obstructions from the tank to the carb and until the final line is connected to the carb everything flows freely and new fuel is fed/pulled from the tank. HOWEVER once you connect the line to the carb it uses the fuel available but doesn't pull more from the tank into the filter. I can watch the fuel being pulled from the inline filter but there is now no new fuel being pulled into the filter. Eventually it starves itself.

Any ideas?!?!?!?!?

 

[ericm979]

Make sure the gas cap is venting. A cap that's not letting air in will slow and then stop fuel flow from a gravity fed system.

 

[pgapro112]

Thanks but I forgot to mention this happens whether the fuel cap is cap is on tight or completely off. I thought of that myself... it's something similar to that though...the system is actively fighting gravity and not allowing the gas to flow freely into the filter however once the fuel line is vented, via disconnecting something, then the fuel runs free.

 

[RjCorazza]

I haven't messed with carbs in years, but wouldn't a stuck float valve result in the symptoms described?

 

[pgapro112]

Yeah, I'm thinking now its more than likely a carb issue... can anyone walk me through the carb part of this as I haven't messed with a carb in years either?!

 

[Diggin It]

I have a 10 or so, maybe more year old 24/48. The past Summer it started doing something similar. It would start and run for a while, then bog and stall. Maybe it would restart, maybe not, but if it did, it ran like garbage, spitting, sputtering, backfiring, etc.. I tried a few things, including replacing the fuel filter and plugs and using fresh gas and adding treatments. Nothing really seemed to help much, or for long. As it was getting towards the end of the season and I was getting more and more annoyed and the deck threw the belt (again), I parked it.

Couple of weeks ago, I started messing with it again. Over the winter I had been thinking valve clearances since they were a problem on the JD. Opened the covers and they seemed to release fine, but I didn't have feeler gauges handy. In the process of putting it all back together, I decided to check the air filter remembering a problem I had with the SCUT. When I pulled the filter, it looked clean, no obvious clogging, but when I whapped it, out came a cloud of very fine dust. Took an air hose to it and got a bigger cloud. Blew it out as best I could, put it back together and cranked it up. Right off, it ran quite a bit smoother. Not perfect, still some backfiring, but smoother than it had been.

Couple of days later I put the mower deck back on after replacing the idlers that had seized. It ran for most of an hour without any problems. Tried it again yesterday and it ran fine. Not great, but better than last year.

I now have a new air filter on order, so we'll see if that does anything. I'm not sure at this point if that's the problem.

If you haven't already, check your valves and air cleaner.