Help with diagnostics

rb608 · Jun 29, 2009

Well, I'm into the summer; and I've managed to keep my grass mowed, despite this weird but chronic problem. I originally posted it as an overheating problem, but I'm less than convinced, and I'd like some advice on continuing to troubleshoot this thing (Cub Cadet 2135).

The basic problem is that it will start and run normally; but will begin to sputter and fail at inconsistent intervals. I've had it run as little as a few minutes to as many as 45. Once it stops, it will not restart within a short period of time. A few hours or overnight seem to be necessary before it will start again.

Here's what I know. The carb, muffler, fuel filter, & air cleaner are new. The problem predated all of these parts, and their installation did not fix it.

Because I initially thought it was an overheating problem, I tried mowing at about 3/4 throttle. That seems to help prolong the operation, but it has not always worked every time.

I have however noticed a few things. First of all, the fuel filter is not full of fuel. When the engine gives up, the fuel filter actually looks empty. Secondly, because I hate pushing the thing all the way back to the barn, when I first sense it starting to run poorly, I shut down the mower deck, and can make it back if I pull out the choke a bit. It still runs like crap, but I usually make it back. In fact, this little bit of choke sometimes "resurrects" the engine for a while; but it won't last.

I don't want to prejudice anybody's opinion, but I'm starting to think it's a fuel issue. I've peered into the gas tank and can find no debris or particles. I don't think there is any obstruction. This problem has also persisted through several fuel tanks of gas, so I don't think it can be bad fuel.

I'm left with maybe a leak in the line from the tank to the filter that's causing it to suck air instead of gas, but I've not seen any evidence of a fuel leak when it's not running.

So who has a test/experiment I can try to narrow thing thing down?

TIA,
Joe

carpenter383 · Jun 29, 2009

rb608 said:
Well, I'm into the summer; and I've managed to keep my grass mowed, despite this weird but chronic problem. I originally posted it as an overheating problem, but I'm less than convinced, and I'd like some advice on continuing to troubleshoot this thing (Cub Cadet 2135).

The basic problem is that it will start and run normally; but will begin to sputter and fail at inconsistent intervals. I've had it run as little as a few minutes to as many as 45. Once it stops, it will not restart within a short period of time. A few hours or overnight seem to be necessary before it will start again.

Here's what I know. The carb, muffler, fuel filter, & air cleaner are new. The problem predated all of these parts, and their installation did not fix it.

Because I initially thought it was an overheating problem, I tried mowing at about 3/4 throttle. That seems to help prolong the operation, but it has not always worked every time.

I have however noticed a few things. First of all, the fuel filter is not full of fuel. When the engine gives up, the fuel filter actually looks empty. Secondly, because I hate pushing the thing all the way back to the barn, when I first sense it starting to run poorly, I shut down the mower deck, and can make it back if I pull out the choke a bit. It still runs like crap, but I usually make it back. In fact, this little bit of choke sometimes "resurrects" the engine for a while; but it won't last.

I don't want to prejudice anybody's opinion, but I'm starting to think it's a fuel issue. I've peered into the gas tank and can find no debris or particles. I don't think there is any obstruction. This problem has also persisted through several fuel tanks of gas, so I don't think it can be bad fuel.

I'm left with maybe a leak in the line from the tank to the filter that's causing it to suck air instead of gas, but I've not seen any evidence of a fuel leak when it's not running.

So who has a test/experiment I can try to narrow thing thing down?

TIA,
Joe

I'm not familliar with your exact model, I always like to check the simple things first. From your description it sounds like a fuel issue. My first thought would be to make sure the fuel cap is vented good. If it's not it will create a vaccume and starve the carb for fuel. Carefully blow compressed air backwards through the fuel line to blow out any dirt. If the fuel filter is getting empty I'd be looking at the lines from there to the tank. You could always bring an air tank with you while you're mowing and when it starts acting up carefully pressurize the fuel tank to see if it helps.

VinceSMTA · Jun 29, 2009

If it is indeed a fuel problem the fuel cap is one area to check. It is an easy thing to check as once the tractor starts acting up us loosen the cap, if it runs better then you've found the problem. One other thing I've found when garage tinkering are ASIAN BEATLES (ladybugs)...they are the perfect size to plug the fuel outlet on the 2000 series tank. Plus they float around in the tank so the stalling out is rather random. Blowing air back through the fuel line will remove the obstruction but over time it will be back. If it were my tractor I would remove the fenders (not too bad of a job) and check the fuel line and/or drain the fuel tank. If that checks out you'll need to check your fuel pump. There is a possibility it could be an ignition problem (coil), but since you say it responds with the choke I'd start with the fuel.

Scooby074 · Jun 29, 2009

Im not all that familiar with your machine, but is there anything electric in the fuel system, like a fuel cutoff or anything like that, that could be getting hot and causing your issue?

savageactor7 · Jun 30, 2009

Yup sounds like a fuel problem. With an empty tank disconnect the fuel line from the tank to the fuel filter and blow it out with some compressed air. If you hold a clean rag over the end of the hose perhaps you'll find the culprit.

rb608 · Jun 30, 2009

Thanks to all so far. To answer a few issues raised -

The fuel cap ventilation was something I'd considered. It's an idea with real merit that does seem to fit the symptom, but I haven't been able to confirm it with "field testing". For some reason, the vent appears damaged; but I've tried mowing with the cap partially unscrewed; but to no avail.

There is no electronic fuel shutoff.

The fuel line exits the tank at the front left of the tank, travels forward a bit through the frame, then crosses behind the engine to the fuel filter on the right. The cross over part is enclosed in a foam insulation sleeve. I've also considered that this cross over may be getting hot enough from the engine to vaporize the gasoline inside the line such that I'm not getting liquid fuel to the engine. I think that's a long shot.

That portion of the fuel line is very difficult to get to, so I haven't checked the portion of the line inside the frame, but everything else looks okay, so I'm narrowing my guesses to what could be going wrong there.

irvingj · Jun 30, 2009

I'm making the assumption that your engine is gasoline, not diesel--?

I'd stick with fuel, too. I once had a chainsaw that would stall out --seemingly randomly-- until I discovered it only happened at 1/2 tank or less; fuel pickup line --inside the tank, no visible leaks-- had a hairline crack that would suck air when fuel was lower, but work fine when tank was full. Never saw it until I pulled the line & happened to flex it in my hands.

You might try running a separate line --temporarily bypass the original-- and see if that clears it up; if it does, then you can replace the original. If it doesn't, then you've most likely eliminated that piece of the puzzle. (Sometimes the inner layer of fuel lines can "collapse" too...remember alcohol in the fuel?)

Does it use a diaphragm type fuel pump, or is it just gravity feed? Is there a strainer on the pickup inside or just outside the tank? Is there a shut-off valve that's getting flaky?

Well, a few suggestions. If you get it running maybe you can help me with a 1971 Honda CB100 that's being very difficult!

Good luck & keep us posted.

savageactor7 · Jun 30, 2009

Joe you don't have to remove the gas line. Jack the rear of the tractor up so the left wheel can be removed. Unhook the gas line from the tank and the fuel filter. Grass or cotton like spider egg nests will eventually work there way the the lowest part of the fuel line.

The safety cans with the long funnel tubes are a magnet for spiders. When you pour the gas you don't notice 'em but over time enough collect in there to restrict fuel flow.

ToadHill · Jun 30, 2009

I hope you post any solution you come up with I have very sim ilar problems with my Huskvarna GT2548.

cubmaster · Jun 30, 2009

rb608 said:
Well, I'm into the summer; and I've managed to keep my grass mowed, despite this weird but chronic problem. I originally posted it as an overheating problem, but I'm less than convinced, and I'd like some advice on continuing to troubleshoot this thing (Cub Cadet 2135).

The basic problem is that it will start and run normally; but will begin to sputter and fail at inconsistent intervals. I've had it run as little as a few minutes to as many as 45. Once it stops, it will not restart within a short period of time. A few hours or overnight seem to be necessary before it will start again.

Here's what I know. The carb, muffler, fuel filter, & air cleaner are new. The problem predated all of these parts, and their installation did not fix it.

Because I initially thought it was an overheating problem, I tried mowing at about 3/4 throttle. That seems to help prolong the operation, but it has not always worked every time.

I have however noticed a few things. First of all, the fuel filter is not full of fuel. When the engine gives up, the fuel filter actually looks empty. Secondly, because I hate pushing the thing all the way back to the barn, when I first sense it starting to run poorly, I shut down the mower deck, and can make it back if I pull out the choke a bit. It still runs like crap, but I usually make it back. In fact, this little bit of choke sometimes "resurrects" the engine for a while; but it won't last.

I don't want to prejudice anybody's opinion, but I'm starting to think it's a fuel issue. I've peered into the gas tank and can find no debris or particles. I don't think there is any obstruction. This problem has also persisted through several fuel tanks of gas, so I don't think it can be bad fuel.

I'm left with maybe a leak in the line from the tank to the filter that's causing it to suck air instead of gas, but I've not seen any evidence of a fuel leak when it's not running.

So who has a test/experiment I can try to narrow thing thing down?

TIA,
Joe

I'm going to say it is your fuel pump, I have seen this before and by choking the engine you are cutting back the air and allowing what little fuel you have in the line to make it to the cylinder. If the engine is actually running hot it is because of a extreme lean condition ( starving for fuel ) I hope this helps you....