Two year saga of suspected fuel-starvation issue on Cub HDS 2135, Kohler 12hp engine

[greynold99]

Deerlane & Packardv8,

Good suggestions.
Ok! I'll be sure to check out the metal fuel tube thru the engine shroud for possible rusted blockage as Deerlane pointed out. I had actually come across that tip Searching this forum but didn't fully understand the implications towards my issue until recently.

Packardv8 - you mention 'EFI grade hose' in your reply and the reason I mention it is, because I don't have a local Cub Cadet dealer, I stopped by a John Deere dealer and picked up couple of feet of 'their' fuel hose, thinking it would be all the same - and when I looked at it more closely, it did not look as well made or as strong as the old hose on the Cub. As I recall, I think the Cub's fuel line hose was made thicker and had reinforcing threads embedded within the hose shell running lengthwise through the entire fuel line.
(At the time I was only thinking I would need the small piece of fuel line from the (new) fuel pump to the metal-tube; so I'll go with OEM Cub fuel line at this point...)

I think we're getting really close to nailing this problem down and I really appreciate your help.
Will post an update when I make any progress.
greynold99

 

[packardv8]

I've confirmed to my satisfaction we're dealing with a classic case of "vapor lock". That is, heat boiling the fuel in the carb and in the fuel line. This boiling raises the pressure to greater than that produced by the fuel pump and no fuel can be pushed through the line.

Yesterday, after thirty minutes of mowing on a 90-degree afternoon, the engine started to slow, struggle and eventually died. To test the vapor lock theory, I took a garden hose and thoroughly washed down the fuel pump and fuel line enough to cool it. It started right up and ran fine for fifteen minutes, until the fuel pump and lines got full hot again. Another cool shower and it was good to finish the yard.

I'll be bypassing the stock steel line going inside the shroud with a flexible line going outside in a slightly less hot environment.

Thinking about it, up here some tractors are used as winter snow blowers/plows and salt spreaders. If using in winter, the steel line through the shroud would prevent carb icing and fuel line freeze-up. I don't use mine that way, but if I did, I'd return to the OEM setup in the winter.

jack vines

 

[greynold99]

Packardv8,

At last I feel some vindication for how this issue has evolved and am glad you've identified what I came to suspect.
To be honest, I really have not been able to do anything service-wise on the tractor for addressing the problem except for removing the Right-side engine cover panel. And that has been sufficient to permit me to mow as much as two hours before any fuel-starvation issues are encountered.
My plan, however is the same as what you've outlined - run the rubber fuel line outside and bypass the metal fuel tube through the engine shroud.

Did you read my question about any difference between the fuel line I picked up at my local John Deere dealer and OEM Cub Cadet fuel line?
I seemed to recall the Cub's flexible fuel line appeared to be constructed better than the John Deere, but actually haven't compared them side by side.

Thanks and talk to you later,
greynold99

 

[packardv8]

Since we're dealing with a low-pressure system, probably either would work. The combination of ethanol added and 40-60 PSI pressure EFI systems are what required upgraded fuel lines for newer cars. The newest direct injection systems require a very special very high pressure fuel line.

jack viens

 

[drivered]

Hi everyone,

For the past 2 years, I've been dealing with what appears to be a fairly common problem with Cub Cadet tractors approaching 500 run hours. They run great for about an hour until the engine gets hot and then start to sputter and die - sometimes you can recover at least to the point that the engine doesn't die by disengaging the mower deck pto and gently choking it to richen the gas mix. Then if it dies, you wait an hour or two, and once it cools off - starts right up and may run an additional 45 min. to an hour before the same chain of events.

All the usual maintenance: new spark plug, coil, air filter, oil/trans fluid changes done last year. Cap has been cleaned and then left off to eliminate the vent issue - some things seemed to help but the problem still happens.

I tried removing the side cover off before mowing last night and without the added heat buildup inside the engine compartment, got 2 hours of mowing and it actually never died out but I didn't want to risk it dying in a location over the hill, where I couldn't push it back to the garage...

Someone has suggested checking the 'Pulse Port' on the fuel delivery - which I'm not familiar with and wondered if it was something someone on the forum might know how to check and if it's associated with the fuel pump?
Thanks,
greynold99

My LTX 1046 does the same thing and it only has 31 hours on it.

 

[mechanic mark]

Cub Cadet Professional Shop Manuals

 

[greynold99]

Mechanic Mark,
Thanks for the link to the shop manuals...

drivered,
I'm not familiar with the LTX1046 model, but 31 hours seems like a very short time to be encountering this issue... Also, if this was an engineering bug with the design, I would've run across a lot more similar posts with this issue.

What have you done to track down the problem?

Few things come to mind that would duplicate the issue in a tractor without having many operation hours..
1. Crap in the fuel tank blocking the outflow connection hole. I don't know how stuff gets in the tank but I found after completely emptying the tank with a siphon hose rigged up so I could get any small pieces of junk on the bottom of the tank picked up was helpful. That pickup outlet hole is a lot smaller than the 1/4" fuel line they use. Look for any fuel line restrictions further down the line up to the connections to fuel filter and pump. Also I replaced those clamp-on fuel line clamps with screw-band type clamps in case it was sucking air at those points.
2. The second thing I was advised to look at were electrical connections to Ground and to the various switches on the tractor that might heat up and lose connection (seat safety switch, reverse switch that disengages the mower when you go into reverse; stuff like that)

You might try running the tractor with the one side-panel off on the side where the fuel line connection to filter and pump are. Not having that excess heat build up really extended the run time for my tractor from a hour to two hours and pointed to the steel fuel line from the fuel pump to the carb on the other side as the culprit. I mean, depending on how your tractor was stored before you bought it - you could already have some rust in that steel line if they use that design on the LTX 1046.

Let us know how it goes.
greynold99

 

[packardv8]

Just to confirm it's a vapor-lock issue, same problem this week and same solution. On a 90+ degree day, after 1/2-hour of mowing, it starts starving for fuel. A quick squirt with the garden hose on the fuel pump and line to cool it down and back to work. Happened three times.

Yes, I've bought the necessary length of fuel line to go around outside of the shroud, as well as a new filter. Just haven't installed them yet. Next week for sure.

jack vines

 

[packardv8]

FWIW, re-routing the fuel line outside the shroud seemed to lessen the vapor lock but did NOT cure the problem. Today I still had two or three instances.

jack vines

 

[greynold99]

packardv8,

I got your update but did not get an opportunity to reply... Sorry to hear re-routing fuel line did not completely and finally resolve the problem...

Just curious, have you tried removing the right (fuel filter/pump) side cover panel from the tractor before you mow and seeing if that extra heat dissipation had any effect?
That seems to allow mine to run for a couple of hours rather than for an hour or less (although I've been scheduling my mowing for the coolest times I can, late afternoon or when a cold front moves through...)

In an earlier post to this thread I had suggested to the owner of a Cub LTX1046 that he siphon all the gas from the tank. I rigged up a 3/8" vinyl piece of tubing on a piece of coat hanger to it, so I could get the bottom of the tank as clean as possible. Hated to waste the fuel but I needed to be able to siphon enough gas so that I could be pretty sure of picking up anything floating or laying at the bottom of the tank or in the gas. Someone had replied on another post that crap getting in the fuel tank or just in the gas when you fill the can is a fairly common problem and that the outlet hole in the tank is small enough, smaller than the 1/4" fuel line diameter and that it can be easily blocked.
I discounted the advice at first, given the exact 1 hour of run-time I had before engine conked out since you'd think it would happen at various times. But when I ran out of other ideas I gave it a try and it did seem to help.

The only other thing I've read that might be related is there was a thread about 'soft' camshaft lobes wearing prematurely on another Cub tractor model. If that's the case, even replacing the fuel pump, which is driven by the camshaft, may not fix the problem.
Good luck,
greynold99