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

[greynold99]

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

 

[Rivets]

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.

 

[greynold99]

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

 

[motoman]

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.

 

[Rivets]

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.

 

[packardv8]

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

 

[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.

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

 

[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

 

[packardv8]

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

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

 

[Deerlane]

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.