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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

On your fuel pump you will find three hoses attached. Fuel inlet coming from the tank, fuel outlet going to the carb and pulse line. The pulse line is what operates the pump, using pressure and vacuum from the crankcase. If the line is cracked or not sealing properly, heat will cause it to expand and reducing the pressure and vacuum to the pump.

Rivets,

Thank you for responding...
That answer's my confusion because the fuel pump I have only has two fuel line connections; the one that comes from the filter and the other end that goes from the fuel pump, connecting to the metal feeder tube thru the engine shroud to the carburetor on the other side.
From the new replacement unit I have, there is also a dog-leg angled piece of U-channel, brass plated coming out the back of the fuel pump where it connects to the engine by 2 small bolts that looks like it's driven up/down by a lobe on a camshaft or something.

I read in a separate post by Packardv8 that he had a somewhat similar issue on a HDS 2135 where he had to replace the cam due to it 'being made softer' and subsequently worn more quickly - but he didn't indicate the exact problem with the heat-connection that I'm experiencing...

Could I ask you another question, and this focuses on the other end near the fuel tank? On my Cub, you can't see much from the back except for the fuel tank cap and it looks like you have to take off the rear seat and fender to get to the whole fuel tank and mounting assembly.
On one of the Cub Cade Parts Supply schematics I found on the web, it looks like there's a component where the fuel line connects to the fuel tank underneath - Have you ever encountered a problem there?
If you've ever removed/replaced a fuel tank - how hard is it to do?

I can't account for the heating component causing the issue from back there but maybe it's a combination of restricted fuel flow and heat.
Anyway, I've already siphoned all the gas out at one point using a hose mounted on a piece of hanger-wire so I could get any solid residue picked up from the bottom and cleaned out the bottom of the tank afterward before filling with fresh gas.
That seemed to help the most but it was a lot cooler back in April/May when I did it.

Thanks for your help,
greynold99

greynold, everyone is concentrating on gas...try cooling the coils with an ice baggie (not wet, like a compress) for five minutes and see if it is better.

Please post your engine model numbers so we can better understand which engine we are talking about. This will also give us the info we need to solve the original problem.

Yes, I've had the identical symptoms on my 1990s HDS 2135 with the 11.5hp single cylinder Kohler. Definitely heat related. Definitely fuel related. As mentioned, fiddling with the choke and reducing the throttle opening can sometimes coax it to run.

But then, maybe sometimes spark related. Less load makes it easier for the spark to jump. I replaced the coil and cleaned the rust off my flywheel and that also helped.

One thing I haven't done is replace the spark plug with one heat range colder. It could be as simple as the plug getting too hot under load on a hot day.

The carburetor has some very small passages and I've had to remove the carb, clean the maybe-ethanol attracted water sediment out of the float bowl and blow out the carb passages.

Also, a new air filter every few months is a good investment. A clogged air filter definitely changes the air/fuel ratio.

It will be an easy and no-cost experiment to remove ALL the front and side sheet metal and see if that has any effect on the heat causing fuel flow problems.

jack vines

motoman said:

greynold, everyone is concentrating on gas...try cooling the coils with an ice baggie (not wet, like a compress) for five minutes and see if it is better.

Click to expand...

Motoman,
Thanks for taking the time to reply...

The ignition coil on a Cub is not easily accessible to apply an ice pack to and requires partial disassembly of the engine cover and drive-shaft shroud assembly before you can even see it.
Unless I'm not understanding correctly or there is some other piece of equipment on other makes of tractors that would be called a 'coil'...

Anyway, if the coil you're thinking about is the one mounted so the flywheel passes between the two-armatures to generate the spark, I replaced that with a new unit last year - and prior to that, never had any problem with symptoms like those I've experienced these last two years.

Given that I've come across at least 5 other similar postings on this forum and the DIY Forum on Cubs starving for fuel, I'm going to try to find that replaceable 'little piece' I came across on a repair parts schematic where the fuel line connects to the fuel tank and see if that would cause the fuel starvation when it gets old & degrades and maybe causes it to obstruct the fuel flow. I think the heating contributes by exacerbating the situation when little fuel is reaching the filter and on hitting the heat in the engine compartment - just vaporizes before it reaches the fuel pump.

Will let you know what I find out.
Thanks again,
greynold99

Had to mow with my Cub over the weekend between rain and the threat of rain... It was cool Saturday and I was able to mow a good two hours with no problem. I still have the right-side panel guard off and I'm sure that has helped disperse the engine compartment heat.

After my last posting, I took a chance and did a Google search on this issue which returned one workaround I hadn't thought of before.
The fella, working on his HDS 2135 with a similar fuel starvation/heating issue, took a 2 ft. piece of fuel hose and routed the fuel line from the fuel pump, where it connects to a metal fuel line thru the top of the engine to the carburetor. Anyway, he takes this separate piece of fuel line through the back side of the firewall to the carburetor.

He indicated afterwards that he didn't have any further fuel starvation issues associated with engine heating.

Anyone have any thoughts on this workaround? Of course, I'm very conscious of the YouTube video showing a HDS 2135 ablaze and wondered if anyone knew how that was caused - it didn't really say on the video?
greynold99

greynold99 said:

Had to mow with my Cub over the weekend between rain and the threat of rain... It was cool Saturday and I was able to mow a good two hours with no problem. I still have the right-side panel guard off and I'm sure that has helped disperse the engine compartment heat.

After my last posting, I took a chance and did a Google search on this issue which returned one workaround I hadn't thought of before.
The fella, working on his HDS 2135 with a similar fuel starvation/heating issue, took a 2 ft. piece of fuel hose and routed the fuel line from the fuel pump, where it connects to a metal fuel line thru the top of the engine to the carburetor. Anyway, he takes this separate piece of fuel line through the back side of the firewall to the carburetor.

He indicated afterwards that he didn't have any further fuel starvation issues associated with engine heating.

Anyone have any thoughts on this workaround? Of course, I'm very conscious of the YouTube video showing a HDS 2135 ablaze and wondered if anyone knew how that was caused - it didn't really say on the video?
greynold99

Click to expand...

So your working theory is vapor lock? Could very possibly be.

As to the safety issues. A longer rubber hose properly routed and secured, should cause no problems. I would use new EFI grade hose and new clamps. Let us know if it solves your problem.

jack vines

The metal feeder tube thru the engine shroud has been known to rust inside. This will shut off fuel from pump. Ethanol in gas attracts water, water rusts metal. I run a rubber fuel line outside the metal shroud from pump to carb on many engines.

Remove soft fuel lines from metal line on engine and get a piece of 1/4" X 18" hose slip on to one end and try to blow threw the to check.

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

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

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

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

greynold99 said:

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

Click to expand...

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

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

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

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

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

Ok! This past weekend I changed over the fuel line to bypass the metal fuel tube through the engine shroud and mounted it on the firewall. While I was at it, I changed the fuel pump as well. Aside from a slight bit of wear on the cam-driven pump-lever coming out the back of the old fuel pump, I couldn't see anything significantly wrong.
The only difference was that the fuel-line connections are now plastic/nylon instead of metal; and you have to use a split-ring tool to depress the internal locking retainer ring so the rubber O-ring seals on the plastic connection nipples aren't damaged when you insert them.

Other than that, pretty much a snap to install.

I ran the tractor a half-hour afterwards to check for any fuel leaks, not enough to verify that it has absolutely fixed the problem but the first thing I noticed was how fast it started up even with the additional length of fuel line. I mean there was almost no cranking before she started up. Plus it seemed like a smoother running condition - no noticeable additional power just more consistent power if that makes sense.

Soon as the rainy period is over here I'll be on it to test the heating/shut-off issue.
greynold99

Running the fuel line around back outside the shroud didn't cure the problem, but today, I removed both side panels and mowed in 90+ heat and no vapor lock! Now, the question is would just removing the side panels have been enough?

jack vines

packardv8,

Well I'm crossing my fingers as I write this - but since replacing the fuel pump and routing the fuel line to the firewall, bypassing the metal fuel tube through the engine shroud; I've mowed maybe 4 times and have had no problems with heat-related engine shut-off. Last time was this past Saturday when the temp was around 87 degrees F.

Though I must admit I've not reset the right side-panel cover - not wanting to tempt fate in thinking I've fixed the problem. But so far so good.

It does take a little bit more extra crank time on the starter to get the fuel through the extra bit of hose needed to route the fuel line directly to the carburetor; but once she starts, she's running.

As I mentioned, the new fuel pump seemed to even-out the fuel delivery for a smoother running engine but no significant change or increase in power as a result. So, it could very well be a combination issue as you thought earlier with the heat and worn fuel pump lever-cam.
If your Cub has any where near 500 use hours on it, might be worth replacing the fuel pump if you haven't done that already.
Later,
greynold99