Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minutes

[ajwgator]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

sounds like your fuel pressure pump is loosing pressure after that 30 minute run time , when it gets hot the pressure drops to below 25 psi or lower , runs very poorly , stops , can re-start after 5 minutes or so and the efi system cannot lengthen the pulse width to compensate ( minimum adaption limit exceeded) and the o2 sensor is sensing the excess air ( lean ) I have seen this very problem in kohler efi mt 26 ghs walker - replace your fuel pressure pump and filter
system fuel pressure should be 39 psi

you can test this by installing fuel pressure gauge at the schrader connection and running engine at full noise with bales running , keep watchin and listen for when the engine starts running poorly , check the fuel pressure gauge , it will be dropping below 25 psi or more and almost stalling and have no power

Pauly50 it helps a lot and glad to hear that someone else has experienced this same problem. I was glad to see you use terms "minimum adaptation limit exceeded" because I had been struggling to really understand what that meant when I read the code meanings in the manuals. I had first went to the TPS sensor (see the first post of the thread) and the readings on the new one were exactly the same as the original one (that was & still installed) so I didn't change it. ILEngine pointed me towards maybe a fuel pump issue which I hadn't even considered before that. I have been posting my experiences & findings to document and help others out here in the future. I am definitely going to change the fuel pump and the filter too.

I'm now trying to get a consensus from others here about using an OEM replacement or better priced (lower) alternatives.

If it is not oem I would not touch an online identically-looking unit. OEM should have sourced a better product. Auto pumps and regulators fail , but not in great numbers (old memories). My experience was if they don't fail near new they go on and on. I have a 1985 Pontiac with its original regulator (45 psi) , and the pump which replaced the new one after it failed. Still running strong. These are not rocket science. I would try a Taiwan, Canada, Australia etc not mainland China.

Thanks motorman. Do you know where I might find the specs of (liters per minute or gals per hr & max pressure output) the OEM fuel pump that Kohler uses? Some of the alternative pumps I have found list pressure close to max of 100 psi and other just say high pressure pumps. Since the fuel pressure regulator after the pump limits the pressure when operating to 39 psi, I'm thinking that 100 psi pump output is quite a bit and maybe too much. Do you think the same or does it really matter as long as the regulator can handle it?

 

[motoman]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

Hopefully IL ENG will respond with specifics. My knowledge is only general. I think you are right to be concerned about "just any" pump. Although the reg "should" be key and provide the pressure the injectors want , with so many later (and higher pressure ) systems you could overwhelm the regulator. I know my 85 PONT wants about 45 psi ( I think), my old Audi wanted 80 (I think) and the current direct injection engines want (?1000). I would grab any Japan sourced part. Sorry cannot provide more. Might look into bike pumps.

 

[ILENGINE]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

From what I can dig up the bosch injection system which would be your system, has a minimum rating of 25 liters/hour at 39 psi. the newer ECH system has a minimum rating of 13.5 liters/hr at 39 psi. Something that may need to be verified prior to confirming the injection pump is bad, is to make sure the lift pump is putting a steady flow of fuel to the injection pump. The older systems used an electric lift pump, and the newer systems use a mechanical, or electric lift pump.

 

[ajwgator]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

From what I can dig up the bosch injection system which would be your system, has a minimum rating of 25 liters/hour at 39 psi. the newer ECH system has a minimum rating of 13.5 liters/hr at 39 psi. Something that may need to be verified prior to confirming the injection pump is bad, is to make sure the lift pump is putting a steady flow of fuel to the injection pump. The older systems used an electric lift pump, and the newer systems use a mechanical, or electric lift pump.

I do believe I have a bosch injection system but not 100% certain, but as far as I can tell I don't have a lift pump in the system at all. The fuel lines on the mower extend down into fuel tank to pull the fuel from the bottom of each tank. The lines then to a manual selector valve (left or right tank),from there through the fuel filter, on to the electric fuel pump, to the fuel pressure regulator, then to an additional fuel filter (I think it has been added by previous owner), and finally to the injector manifold.

Concerning the pressures, yes the 25 lph @39 psi is what is required for proper operation of the engines with EFI systems, but I was trying to find out what pressure the electric fuel pump puts out before being regulated. Any excess pressure is bled off and sent back to which ever fuel tank is selected through the manual selector valve.

What I'm trying to find out is the maximum pressure the OEM electric fuel pump produces before the output is regulated by the fuel pressure regulator. For the sake of discussion, if the OEM fuel pump max press is 50 psi and I replace it with an alternative brand but its max press is 100 psi, would this cause problems such as overwhelming the fuel pressure regulator? (I may be worrying too much) I really hate having to pay $200 for an OEM fuel pump when I have found new high pressure electric fuel pumps for a third of that price.

Hope that better explains what & why I am trying to find out.

 

[ILENGINE]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

the service manual talks about a lift pump, but the parts diagram for your engine doesn't list it. Kohler is not forthcoming on the specs of their fuel pump, so I don't know what to tell you about the full output pressure. One thing about using the OEM pump though even though it may be more expensive is you know it is the correct pump with the correct outputs specs.

 

[motoman]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

A random thought. Don't know about "lift" pumps, but my Pont, and Nissan have gas tank immersed pumps which pressurize the entire plumbing right to the injectors. Maybe IL ENG can explain why they use a lift pump on a relatively small system?

 

[ILENGINE]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

The first Kohler EFI engines had the pump mounted on or near the fuel tank. So maybe the charge pump was built into the injection pump. the newer Kohler ECH engines have the injection pump mounted on the engine and use a mechanical or electric pump to supply fuel to the injection pump since it isn't self priming.

 

[ajwgator]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

The first Kohler EFI engines had the pump mounted on or near the fuel tank. So maybe the charge pump was built into the injection pump. the newer Kohler ECH engines have the injection pump mounted on the engine and use a mechanical or electric pump to supply fuel to the injection pump since it isn't self priming.

Like you said ILEngine, the IPB for my engine doesn't show or list a charge pump. Both the Kohler & the Gravely IPB I have only show the injector pump. It is mounted on the frame/platform in front of the battery and is between & below the two tanks. The fuel lines in the tanks exit from the tanks almost at the top so they definitely do not gravity feed. The intake fuel line comes from the tank selector valve that is mount on the front panel under the seat. Each fuel tank has a supply & return fuel line that goes to the selector valve. No evidence of a charge pump anywhere that I can find. Wiring diagram for the mower doesn't show any either. When I turn the key to the on position the injector pump comes on, builds pressure to 41 psi and continues to run for another 10 seconds or so then turns off. Then it comes back on to repeat the cycle two more times. I can hear fuel running back into the fuel tank once the pressure get to 41 psi. The Kohler manual states this is the purge cycle that takes place when ever the key is turned on without starting the engine.

In my opinion the injector pump has to be powerful enough to suck the fuel from the bottom of the fuel tank, up to the top of the tank, on out through the selector valve, filter, and to the intake of the pump. As long as there is fuel in the tank and all the fuel lines have been purged of any air this task of sucking the fuel shouldn't be much of a problem. Simple physics so I really don't see a need for a charge pump as long as the injector fuel pump is supplying an excess of 39 psi +/- 3 psi. The excess is directed back into the fuel tanks from the fuel pressure regulator. I may have already said all this in a previous post and if so, sorry for repeating myself.

Still having a hard time considering an OEM replacement pump for $200.... but might just have to bite the bullet! The way it stands now I can always just mow for 30 minutes and take a little break...lol

 

[pauly50]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

hi , the lift pump is only lifting fuel from the tank, with no appreciable pressure and the output from the lift pump is filtered with a pleated paper filter 10 micron filter
and supplied to the pressure pump , the pressure pump supplies fuel to the metal can filter before the injectors ( injector filter screen can block up too) ( the filters inside the pressure pumps are 20 micron ) and can block up , pick up filters inside the tank are 75 micron i think the lift pump number is 808656 the number on the pump , these pump are vacuum and pressure pulse activated via the positive and negative crankcase pressures

is your system a in tank pump and regulator system or internal pick up and external pressure pump , with return line to tank and is the fuel pump mounted under the tank inside the chassis rail or on the rear cross rail behind the no2 cyl ? if it was me i would be putting kohler oem pump on , if using non oem pumps with higher output pressures can run into problems ie causing regulators to fail , possible overfueling , running rich

hope this info helps with your decsion


cheers pauly50

 

[bertsmobile1]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

A random thought. Don't know about "lift" pumps, but my Pont, and Nissan have gas tank immersed pumps which pressurize the entire plumbing right to the injectors. Maybe IL ENG can explain why they use a lift pump on a relatively small system?

To limit the amount of high pressure fuel line to a minimum.
The mower will shake areound and bounce around a lot more than your car.
Common method for most deisel engines for donkeys years.

Have seen some equipment where the lift pump inside the fuel tank is not replaceable as it went into the tank before the tank was welded together.
Thus it is part of the tank assembly so will not show as a seperate item in a parts listing.