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View Full Version : Kohler CV730 looses power uphill under load


strysnie
04-10-2007, 01:44 PM
My first post here, I've read lots of useful info but cannot find anything on the problem I am having.

Motor is a Kohler CV730, 25hp in a Sears tractor. About 250 hours on it, all maintenance up to date. Recently replaced a head gasket, but the problem I am about to describe was the same before and after I did the head gasket.

Problem is I loose power/RPMs under load going uphill. Even slight grades are an issue. Steeper grades take me to the point of stalling unless I slow to a crawl. The same grades are not an issue if the deck is disengaged, so without that extra load there is no problem.

There are no obvious external signs from the motor, no backfiring, no missing, no smoke. It just progressively slows until I remove some load by going really slow or disengaging the deck. The problem clears within a few seconds when I return to level or turn downhill or disengage the deck.

I dropped the deck, cleaned, and inspected all of the bearings and belts. Everything is fine, no loose bearings, all spin smoothly by hand. I think this rules out excessive load from the deck components.

Next thought was fuel starvation so I pulled the carb, float level matches spec, and everything is clean. Fuel system is clean all the way from tank to carb and fuel filter is new. I swapped the fuel pump from a working tractor but this made no difference. Air filter is new as well. The choke, throttle, and governor mechanisms appear to be working correctly.

Plugs look fine, dark grey but no oil or soot, I'm not thinking they are indicating overly lean or rich. Battery is healthy with a full charge.

I'm going to make a leakdown tester next to see if there is a valve or ring issue, but I really do not expect anything here with only 250 hours on it. When I had the one head off to replace the gasket the cylinder and valves looked pristine.

Has anyone experienced something like this? Any troubleshooting tips?

ChadsLawn
04-10-2007, 02:43 PM
Sounds to like maybe your trying to cut tall/thick grass too fast. Is the deck getting clogged when your cutting? That could also be part of the problem.

Is the govenor(sp) set properlly?


Thats about all I can think of at the moment. Hope it helps..

khouse
04-10-2007, 03:27 PM
Put a set of plugs in it. You may have one breaking down under full load. It's harder for a spark to jump a rich environment. If that does'nt do it I have one more thing to try. Sounds like you covered most of the obvious areas.

Restrorob
04-10-2007, 07:05 PM
If that does'nt do it I have one more thing to try.

The floor is your's khouse....

strysnie, Welcome to LawnSite !

That's some good trouble shooting you performed and a well put together thread.

khouse
04-10-2007, 07:37 PM
Well, my first thought was that it was starving for fuel. But he said he had checked that. So then I thought that one plug was breaking down under load or one coil or coil wire. So I thought the plugs was the easiest thing to eliminate. Then I was going to move to the coils.

strysnie
04-10-2007, 08:38 PM
Yeah it does behave similar to when trying to cut too much or too quickly. I should have mentioned that I have this problem even when not cutting grass, like going back up a strip that has just been cut. Deck is clean and everything down there is spinning freely so I do not think that is the problem.

I do believe the governor is set ok but it is hard to say for sure that it is working correctly as I cannot watch it while the problem occurs. It responds as expected when I play with it sitting still. I've been thinking of rigging something up so I can see what the governor is doing when I have the problem, maybe put some kind of indicator on the throttle linkage that I can watch while driving.

Sounds to like maybe your trying to cut tall/thick grass too fast. Is the deck getting clogged when your cutting? That could also be part of the problem.

Is the govenor(sp) set properlly?

strysnie
04-10-2007, 08:41 PM
I will give that a try, I do have a new pair of plugs on the shelf.

I also have another working tractor with a Kohler 22, I will look at the coils on that engine to see if I can swap them to eliminate any coil issues.

Put a set of plugs in it. You may have one breaking down under full load. It's harder for a spark to jump a rich environment.

khouse
04-10-2007, 09:39 PM
It does'nt sound like your governor has issues. It's just really tough to diagnose engines with written words. If we only could put our butts in the seat and our hands on the engine! One "old farmer" way to check the coils under load is to connect a timing light up to each coil wire. Then watch the light as you pull that hill. This can tell you if the coil is breaking down under load. Don't forget to check both coils. Don't look directly into the timing light as your head will explode!

strysnie
04-10-2007, 09:48 PM
Thanks guys for the warm welcome and the ideas - I have a few things to try based on the above.

I did try the new plugs this evening but they did not make a difference. I'll try to get through the other ideas over the next couple of evenings.

Bill Kapaun
04-11-2007, 03:03 AM
You said you used a new fuel filter. Did you use the correct KOHLER filter?
On another website, there have been a couple cases of Kohlers not even starting when the correct KOHLER filter wasn't used. I don't know why, but it's apparently happened for some reason.

pugs
04-11-2007, 09:15 AM
How steep are the hills? How much fuel was in the tank? Where is the tank? I am just wondering if the fuel is moving away from the pickup or sump or whatever when you hit these hills.

stronics
04-11-2007, 07:04 PM
strysnie,
Did I understand that you put on a new fuel filter? If it isn't the correct one it will do exactly what your experiencing. A Fram filter with the hose kit with them will not work and I have found that some paper element filters won't. Once they swell up from the gas the engine will not get enough fuel. And the problem your having is fuel related.
David

strysnie
04-11-2007, 08:19 PM
Dave and Bill, yes good idea on the filter but I am using the Kohler one listed for this engine. I can see how a more restrictive filter could cause the problem I'm having.

strysnie
04-11-2007, 08:27 PM
Good thoughts but I think the fuel delivery system is ok... I'm running with a full tank of fresh fuel. The tank is under the seat, I have already removed/drained it and checked the pickup (really just an elbow). I did not try flushing out the line from the tank to the fuel filter, I could blow some compressed air through there to see if any blockage exists. I'll add this to my list of things to check. There is no screen on the fuel pickup so it is possible that something got into the line and is clogging it.

The hills are really not that steep, I can recreate the problem going up my driveway which rises maybe a foot every 10 feet. I have some lawn areas steeper than that, but this same tractor did fine on them for the first 240 hours or so, problem just appeared in the last couple of times I used it.

How steep are the hills? How much fuel was in the tank? Where is the tank? I am just wondering if the fuel is moving away from the pickup or sump or whatever when you hit these hills.

Restrorob
04-11-2007, 10:52 PM
What is your wide open no load RPM set at ?
Are you mowing at wide open throttle ?

Bill Kapaun
04-12-2007, 05:00 AM
Is the fuel pump "pulse" line intact? NO LEAKS ANYWHERE!???

strysnie
04-12-2007, 03:36 PM
I spent some more time on it today - fuel pump pulse line was intact and clear, fuel line from tank to filter was clear. Compression was around 165psi on both cylinders.

So I moved on to the coils, I was going to swap them with another engine I have. Before I took them off I noticed that the kill wire on one of the coils was on a different terminal that the other coil. That was the problem. I must have put that wire back on the wrong terminal while doing some maintenance a few weeks ago. I verified this by swapping the wire a couple of times and having it on the wrong terminal was definitely the cause. I used the mower for a couple of hours today with no problems.

So khouse you were definitely on the right track. Just instead of a failing coil I had made a wiring error. This alters my normal thinking of ignition as a binary system - either working or not. It was running so smooth a lower loads that I was focusing on the fuel system instead of the ignition. Good lesson learned.

Thanks again to everyone for your inputs. If nothing else this turned out to be a great thread for general Kohler 25 troubleshooting advice.

khouse
04-12-2007, 03:44 PM
I'm glad it's working! I probably would have missed the wire. Good thing you found it. I can tell your a good wrench bender. You just came to a fork in the road. It happens to all of us. Take care.
Kenny

thecrankshaft
04-12-2007, 07:08 PM
I always wondered if a Command 25 HP would power a Sears tractor only running on one cylinder, as 25 HP is wayyyy more than some of these tractors need.

The twins run very smooth on only one cylinder. There are some crude ways to test to see if it is only running on one cylinder as well.

What wiring did you mess up? - I'm curious

strysnie
04-13-2007, 11:41 AM
I messed up the kill wire connection to one of the coils (technically these are "ignition modules" but it seems that most folks refer to them simply as coils). Each coil has 3 terminals on it, 2 on one side and 1 on the other.

Looking at the Kohler manual I think the pair of terminals are there for testing purposes. That's the only reference I see to them, in a troubleshooting table. I could not find any text or diagram that explained the purpose of the 3 terminals. By process of elimination I figured out that the single terminal is the one the kill wire goes to. If the kill wire is on one of the other terminals it seems the spark is degraded enough to cause the problem I initially described.

pugs
04-13-2007, 02:09 PM
I dont think they use the same coils on the other system...but Kohler makes whats called "Smart Spark". The modules look very similar to the regular ones and the system uses a 3rd external "black box" that advances/******s the timing of the ignition system. I know those modules have a few connections on them, but I never looked to see if those modules are used in applications that do not use the Smart Spark box.

esignman
10-18-2013, 01:05 PM
This thread is pretty old. I hope the contributors are still around. I have the exact same symptoms. Same tractor, (GT5000), same engine CV730. The only difference being that I've never removed the kill wire from the suspet ignition module but you better believe that I'm going to check it tonight. I had a mouse problem. They ate all the insulation from every wire under the hood and they ate clean through an ignition wire. I replaced the eaten ignition wire with a new module but never touched the other module. So from what I've read: after I confirm the IM kill wires are on the correct terminals, the next step would be to replace the plugs. Failing a resolution here, should I replace the second ignition module? A little expensive to shotgun tho....Oh, I'm not sure that I understand what I'm looking for with the timing light....

Jeff in AL
10-18-2013, 09:06 PM
This thread is pretty old. I hope the contributors are still around. I have the exact same symptoms. Same tractor, (GT5000), same engine CV730. The only difference being that I've never removed the kill wire from the suspet ignition module but you better believe that I'm going to check it tonight. I had a mouse problem. They ate all the insulation from every wire under the hood and they ate clean through an ignition wire. I replaced the eaten ignition wire with a new module but never touched the other module. So from what I've read: after I confirm the IM kill wires are on the correct terminals, the next step would be to replace the plugs. Failing a resolution here, should I replace the second ignition module? A little expensive to shotgun tho....Oh, I'm not sure that I understand what I'm looking for with the timing light....

esignman,

What are ALL the numbers off your engine, Model, Spec. and Serial?

The reason I ask is Kohler has used several different coils/setups through the years. Depending on which version coils you have, it is possible that you may pay more for one coil of an older style that are prone to fail then to upgrade both coils to the almost bullet proof style they have gone back to that had almost no failures... Unless, mice eat the wires. :)

esignman
10-19-2013, 07:55 PM
Hi Jeff,

Model CV730S
Spec: 0017
Serial:3326617101
OEM Product Number:185615

The new Ignition Module that replaced the "eaten" module is 24-584-45-S CDI FIXED.

I also installed a new breather and breather hose, (old hose was cracked). I took the cover off last night and my wiring to the kill wire is the same on both sides. It goes to the single terminal. The other side of the IM has a double terminal, (unused).

My next step will likely be replacing the plugs, just because....

Do you think my remaining/old IM is bad or weak? Is there a way to test this?

thanks__mike

Jeff in AL
10-20-2013, 07:38 PM
Hi Jeff,

Model CV730S
Spec: 0017
Serial:3326617101
OEM Product Number:185615

The new Ignition Module that replaced the "eaten" module is 24-584-45-S CDI FIXED.

I also installed a new breather and breather hose, (old hose was cracked). I took the cover off last night and my wiring to the kill wire is the same on both sides. It goes to the single terminal. The other side of the IM has a double terminal, (unused).

My next step will likely be replacing the plugs, just because....

Do you think my remaining/old IM is bad or weak? Is there a way to test this?

thanks__mike

Mike,

I didn't forget about you... I will check the info I have at work, but I'm pretty sure the coil you have just has 1 terminal on it with a white ground wire to kill it... You say there are 3 terminals, but only one terminal is being used?

piston slapper
10-20-2013, 09:17 PM
I believe you're right Jeff....the coil he just bought is a standard induction coil...
If the other coil has 2 or 3 prongs on it...something is amiss....I'm guessing there's a black ignition box on it too...
To identify which ignition setup yo,u should have....identify the flywheel..
Near the flywheel bolt ....there will be a drilled indent...a drilled thru hole...or no drilled marks at all..
No drilled marks....standard coils...1 prong coils
Drilled indentation.....SAM ignition...2 prong sam coils..
Drilled thru hole.....DSAM ignition ...2 prong dsam coils...
Ventilated slots in flywheel...DSAI ignition....3 prong dsai coils..

esignman
10-21-2013, 07:22 AM
Here's a picture of the new coil. It looks exactly the same as the old coil. It's installed upside down in relation to other coil. The white wire is attached to the bottom terminal, (you can't see it here) on the top, which you can see are two other terminals that are unused. Piston Slapper, the only way for what you're saying to be true is that if I got this from Sears with the wrong coils. Possible I guess but it did run correctly for several years.

The original problem in this thread from Strysnie had three terminals as well and he found that he had put the wire on the incorrect terminal. I have the three terminals but the wire is correctly placed.

Jeff, I have to travel for work this week but will be watching this thread. I just won't be able to try anything.

It looks like this site won't accept a jpg and I have to catch a plane and cannot figure this out at the moment. I'll try to add the pic later.

Thanks__esignman

esignman
10-21-2013, 07:44 AM
Ok, got a handle on uploading pics. The first pic is of the original and remaining coil. You can see that the kill wire is attached to the single terminal on the top. If you look closely you'll see two more unused terminals on the bottom. The second pic is of the coil I just replaced. You can see the two unused terminals on the top. Like I said, they are exactly the same physically. Hope this sheds some light.

esignman

Jeff in AL
10-21-2013, 09:28 AM
Here's a picture of the new coil. It looks exactly the same as the old coil. It's installed upside down in relation to other coil. The white wire is attached to the bottom terminal, (you can't see it here) on the top, which you can see are two other terminals that are unused. Piston Slapper, the only way for what you're saying to be true is that if I got this from Sears with the wrong coils. Possible I guess but it did run correctly for several years.

The original problem in this thread from Strysnie had three terminals as well and he found that he had put the wire on the incorrect terminal. I have the three terminals but the wire is correctly placed.

Jeff, I have to travel for work this week but will be watching this thread. I just won't be able to try anything.

It looks like this site won't accept a jpg and I have to catch a plane and cannot figure this out at the moment. I'll try to add the pic later.

Thanks__esignman

Ok, got a handle on uploading pics. The first pic is of the original and remaining coil. You can see that the kill wire is attached to the single terminal on the top. If you look closely you'll see two more unused terminals on the bottom. The second pic is of the coil I just replaced. You can see the two unused terminals on the top. Like I said, they are exactly the same physically. Hope this sheds some light.

esignman

Mike,

Ok, I see where the confusion is from now...

First off, the correct coil for your engine is in fact the 24 584 45-S which has a single push on terminal.

The "other two terminals" that you see are NOT terminals, but rather grounding legs from inside the coil that are spot welded to the laminations.

For reference, here are a few pictures of the coils... 1 verses 3 terminals (I didn't pull a 2 terminal coil).

esignman
10-21-2013, 01:23 PM
Mike,

Ok, I see where the confusion is from now...

First off, the correct coil for your engine is in fact the 24 584 45-S which has a single push on terminal.

The "other two terminals" that you see are NOT terminals, but rather grounding legs from inside the coil that are spot welded to the laminations.

For reference, here are a few pictures of the coils... 1 verses 3 terminals (I didn't pull a 2 terminal coil).

Ok, so at least I'm working with the correct parts. Thank you for looking that up!
Posted via Mobile Device

Jeff in AL
10-21-2013, 07:32 PM
Ok, so at least I'm working with the correct parts. Thank you for looking that up!
Posted via Mobile Device

Mike,

Yes, you have the correct coil(s) on that Spec.

So with all that said, you now have 1 new coil, 1 original coil and have repaired ALL the chewed wires and still have a problem with the engine?

If so, you can replace the plugs as you wanted to (Champion RC12YC), get you a spark tester from any autoparts store and check the fire on each plug and see if both are firing the same... If the problem your having is only when engine is hot, then run the engine until the problem happens, then check for fire on both plugs.

Also make note of or post pictures of the old plugs... Are they both black, is only 1 black, which side was the black plug on and so forth.

Have a safe trip, we'll be here when ya get back!

esignman
10-25-2013, 10:29 AM
OK, On my way out to buy the plugs and a spark tester. Not sure about the spark tester. The only time the problem occurs is when the deck is engaged and I'm travelling up hill. Not sure I have the capacity to do all that.

Attached are pictures of the plugs, the one on the left is the suspect which is connected to the original IM. The plug on the right is connected to the new IM. I noticed that the suspect is a little wet. They both look the same to me beyond that.

esignman
10-25-2013, 10:37 AM
Actually upon a stronger inspection, the suspect plug looks less worn, maybe even newer. The center electrode is shiney and the insulator is clean as if the plug were new or not firing. Also the wetness suggests that plug was not firing. The plug connected to the new IM has a black, (carboned up) electrode and the insulator is yellowed, (as if from heat). Do I have another bad IM?

esignman
10-25-2013, 01:11 PM
That was it. Bad plug under load. Both plugs, both sides sparked against the block but the one plug that was wet was the likely culprit. Replaced both plugs and the machine now drags my fat arse up hill under load without loosing so much as a single RPM. Thank you both so much! I learned a quite a bit from you.

Esignman

Jeff in AL
10-25-2013, 02:52 PM
That was it. Bad plug under load. Both plugs, both sides sparked against the block but the one plug that was wet was the likely culprit. Replaced both plugs and the machine now drags my fat arse up hill under load without loosing so much as a single RPM. Thank you both so much! I learned a quite a bit from you.

Esignman

Esignman,

Glad to hear ya got it going!

IF the problem comes back, check the coil for that the left plug in the pictures. It is possible to foul out and not fire as appears to be what happened. However, it is very possible you may have a coil issue on that side causing the plug to be "wet" and foul out.

Jeff

esignman
10-25-2013, 04:31 PM
OK, I'll watch it and remember this. I just finished the whole lawn and it performed beautifully. If this plug reacts the same then I'll switch out the IM. I'm optomistic tho.

esignman

Jeff in AL
10-25-2013, 04:50 PM
I agree, I wouldn't just throw a coil on it if it doesn't need it right now... Just wanted you to be aware that you still might have a coil issue.

If it ain't broke, don't fix it :)

Jeff

esignman
10-26-2013, 09:50 AM
I agree, I wouldn't just throw a coil on it if it doesn't need it right now... Just wanted you to be aware that you still might have a coil issue.

If it ain't broke, don't fix it :)

Jeff

Jeff, Do you think the coil could possibly be burning out the plug? Bottom line is, if it happens again then the next step would be to replace the IM.

Esignman

Jeff in AL
10-28-2013, 08:02 PM
Jeff, Do you think the coil could possibly be burning out the plug? Bottom line is, if it happens again then the next step would be to replace the IM.

Esignman

Sure it is possible for the coil to get weak when hot... You should notice a decrease in power though I would think... Of put a spark tester on it and check it and compare to the known good side.
I don't think you have any other issues at this time with leaking gaskets, valves, headgasket but just a possible coil issue.

See how it goes and if you have problems again, post it again!

Jeff

esignman
10-28-2013, 08:31 PM
Thanks Jeff...Go Red Sox!

Jim in Mass
08-08-2014, 07:10 PM
Replaced MDI module 32 707 01-S, tractor ran briefly. I now have no spark on either side. Mower is not running at all now.