The Green Industry's Resource Center

Aussie12 · #1 08-06-2011, 12:35 AM

I have 3 walker mowers MTGHS all with 26hp EFI Kohler engines model CH26S. I bought this particular motor as part of a package buy of 2 walker mowers, 1 running and 1 not, so I have never seen this engine running (yet) the guy I bought it off said it ran fine but he was having problems with the fuel pump and just shelved it.... ok so my main machine just broke a crank shaft... 1.5 inch shaft broken clean through just inside the sump housing with only 750 hrs on it! ... anyway I have exchanged the broken crank engine with this one I have never seen running.... it turns over fine, it has spark but the fuel is not getting through... remember this mower was just running before I broke the crank in the other engine so it is nothing to do with the cpu or fuel pump, I can here the pump cycle just as normal...the wiring seems fine I checked it all twice.... but it seem as if the injectors are either clogged or are not working because of some electrical issue... I assume they work by recieving a signal from the TPS which I have replaced with a new one (not an original Bosch part but an equivilent) I can get it to fire up by putting fuel into the air intake but have no throttle control and the engine dies as soon as the small amount of fuel runs out, I am not a mechanic and will happily supply any additional information needed to help me get this thing running asap..... I guess my question is, is there anything electrical that would stop the injectors from letting fuel through? Or should I just pull it out again and remove the injectors for cleaning?

Thanks in advance, Les.

Snapper Jack · #2 08-06-2011, 08:08 AM

The TPS(Throttle opening) sends signal to ECM ,then ECM sends a pulse signal to fire the injectors for exact amount of fuel to be injected.( Just the basic format) There should be a fuel regulator some where near the fuel rail, need to find the exact fuel PSI required and test yours. Need to see if the injectors are getting a fire pulse command from the ECM.

fixer67 · #3 08-06-2011, 08:19 AM

Quote:

Originally Posted by Snapper Jack

The TPS(Throttle opening) sends signal to ECM ,then ECM sends a pulse signal to fire the injectors for exact amount of fuel to be injected.( Just the basic format) There should be a fuel regulator some where near the fuel rail, need to find the exact fuel PSI required and test yours. Need to see if the injectors are getting a fire pulse command from the ECM.

Kohler EFI runs at 40 PSI. Fuel pump is contoled by the computer though a relay. Turn the key switch on (do not start) you should see the ECM do a self test by turning the fuel pump on for a few seconds and then off. It will do this a few times until the system times out. If the fuel pump does not run at this point then find and test the relay. If the post pictures of your system I will help you find the right relay to test. On the older metal cased ECM the fuel pump relay is under the seat at the bottom of the ECM. On the new ones the fuel pump realyt is monuted at the top of the plastic cased ECM just in front of the blower box.

How long has it been sence the fuel filter was changed? They are rated at 1500 hours (hard to believe but that is what the books says) but I have seen more than one get clogged to the point that the fuel pump would not work.

Aussie12 · #4 08-06-2011, 10:01 AM

ECM, eletronic control module?... "Need to see if the injectors are getting a fire pulse command from the ECM." Thats right SJ do you know any way of doing that?

Fixer this mower was running another engine just 2 days ago, the pump and relays work fine there is plenty of fuel preassure .... all filters work best when dirty, fuel air or whatever type they just filter more and more until there is no flow .... no flow is easy to detect and one of the first things I would check for... I have flow but it is not getting past the injectors and into the cylinder .... when i squirt fuel into the air intake the engine will fire up briefly.

pugs · #5 08-06-2011, 11:23 AM

You said you changed the TPS? That could be the issue. There is a procedure for initializing a new TPS sensor. Different procedure depending on exactly what ECU you have I think. I dont mess with enough of them to keep the knowledge in my head. Grab the service manual and look at section 5b or whatever the EFI section is. It will be in there.

Restrorob · #6 08-06-2011, 11:56 AM

Quote:

Originally Posted by pugs

You said you changed the TPS? That could be the issue. There is a procedure for initializing a new TPS sensor. Different procedure depending on exactly what ECU you have I think.

Ding ding ding...... And we have a win'a !

The easiest fastest way to get this machine up and mowing is to treat this replacement engine like a long block, Swap your known working complete intake with injectors and TPS/crank position sensor harness and all to the replacement and call it a day.....

Snapper Jack · #7 08-06-2011, 03:06 PM

Quote:

Originally Posted by Aussie12

ECM, eletronic control module?... "Need to see if the injectors are getting a fire pulse command from the ECM." Thats right SJ do you know any way of doing that?

Fixer this mower was running another engine just 2 days ago, the pump and relays work fine there is plenty of fuel preassure .... all filters work best when dirty, fuel air or whatever type they just filter more and more until there is no flow .... no flow is easy to detect and one of the first things I would check for... I have flow but it is not getting past the injectors and into the cylinder .... when i squirt fuel into the air intake the engine will fire up briefly.

What I have uses a two led wired that inserts to make contact with the lead terminals of the female injector connector. This sends voltages to a 12V bulb that pulses the bulb. Should be able to pick one up any auto parts store.
Also listen to the advice given by other members who are familiar with the Kohler EFI system.

Aussie12 · #8 08-07-2011, 07:10 PM

I was able to test the power signal to one injector .... it is getting a signal ... thanks SJ ... I am guessing it is blocked injectors, it had some pretty $#!+/ looking fuel in the tank of the mower it came from and if any that ever did get in there.... well

I read about the TPS initializatioin and if I understand it correctly it needs to be running in order to do that ... thanks pugs.

Restrorob .... I dont know why I didnt think of that! Probably too tired ... Good job.

Engine out ... again :-(

But I have another question for you guys .... I am in the process of pulling the broken crankshaft out of the other engine and I am looking at the engine speed sensor on the flywheel .... I think it is on backwards! There is a picture in the service manual (section 5b) which shows the lead wire running back towards the engine and the small bolt in the sensor facing outwards ..... there is only around 1/4 to 1/3 of the sensor sitting directly above the flywheel on mine ... it just doesnt look right .... the lead wire on mine is facing out and the little bolt is facing in .... is there any real reason why somebody might have done this ... other than total incompetence?
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