Frustrating Intermittent Problem with Scag Turf Tiger Koehler Engine

EngineMan · Aug 7, 2013

Start with the bad fuel and heat shield, renew the fuel pipe and fit some heat shield material between the pipe and engine and then try it, have you got a manual for that engine..?

JRonascag · Aug 7, 2013

I have the basic manual that came with the mower. I replaced the fuel line and applied heat shield tape over whole length. Now I just have to wait for the grass to get high enough to challenge the mower. Will be a couple weeks dang it...
Thanks to all for the great help and I'll keep you posted.

EngineMan · Aug 7, 2013

This may help you.

https://www.dropbox.com/s/7nsje7myszbbovb/SM_2469006_CH18_thru_CH750_REV1_12.pdf

Fish · Aug 7, 2013

Well, your engine has "Smart Spark" or the S.A.M. module, so hopefully you found your engine's problem. If not, you might just take a quick look at the backside of the keyswitch, many mowers that have had on-off SmartSpark troubles had badly corroded keyswitches.

JRonascag · Aug 8, 2013

Wow! That manual is MUCH better than what I had. Thanks EngineMan!

And Fish, I'll give the ignition switch a look next time I'm at the mower. Sure hoping the fuel line was my problem, but will let you know how it comes out.

I'm curious though: Apparently the Smart Spark system has significant issues?

Thanks again. This is a great Forum!

Fish · Aug 8, 2013

JRonascag said:
Wow! That manual is MUCH better than what I had. Thanks EngineMan!

And Fish, I'll give the ignition switch a look next time I'm at the mower. Sure hoping the fuel line was my problem, but will let you know how it comes out.

I'm curious though: Apparently the Smart Spark system has significant issues?

Thanks again. This is a great Forum!

Yeah, it is a different critter. Unlike all of the other ignition systems, this one requires voltage to be supplied to the S.A.M. module for it
to function correctly, and old corroded connections can wreak all kinds of havoc.

They just came up with a system where it has an extra hundred things that could go wrong......

JRonascag · Aug 8, 2013

Interesting (and somewhat discouraging). So here's a possibly dumb question: If proper voltage is critical for the Smart Spark function, does that mean that a fully-charged battery is a key to this engine running properly?

Fish · Aug 8, 2013

JRonascag said:
Interesting (and somewhat discouraging). So here's a possibly dumb question: If proper voltage is critical for the Smart Spark function, does that mean that a fully-charged battery is a key to this engine running properly?

It can be a problem, which is why I ask questions about the mower, like if it has an electric pto, as that can drain a lot of juice.

The Smartspark requires a lower voltage minimum to operate correctly, like 10 volts or so.

But corroded connections or damaged wires are usually the problem, as they can drop voltages as well.

If the overall voltage drops too low, the pto usually starts cutting out first, but not always....

Keith O · Sep 8, 2019

JRonascag said:
Hi! I'm new to this forum, so I apologize in advance if I do something wrong with this post. I have a frustrating problem with my Scag and am sure hoping you can help:
It is an ~8-yr old Scag Turf Tiger with the 27hp Koehler engine, with ~300 hrs. I use it to cut my 5 acre lot.
I've always maintained it carefully and it's been a great mower. Now however, it's developed a very frustrating intermittent problem as follows:
The mower/engine runs perfectly for about the first hour. Then, right out of the blue, it starts sputtering and quickly dies if I don't quickly kill the blades and put the throttle to idle.
If I let it idle for a minute or so, then I can resume cutting for 15 minutes or so with no problems. Then...it starts the bobbling again. If I let it cool completely (i.e. overnight), it will run great for the hour or so and then start the issues again.
I thought I had found the problem: a clogged oil cooler. Embarrassingly, I hadn't noticed that it had developed a small leak at the cooler inlet and oil had dripped onto the fins, allowing it to collect a lot of dust, and the fins were completely clogged. I felt sure this was the problem, causing it to get too hot and shut down (heat or oil pressure sensor I hope?). I removed the cooler, cleaned it and the flywheel housing and fixed the leak, thinking that this would solve the problem. It definitely seems to have helped as it runs considerably longer (about 1.5hrs) before the problems starts again. One other item: I can't tell for sure, but the power also seems to be down a bit overall. It seems that the engine chokes down a little when I do a lot of hard turning and I don't remember that occurring before.
As FYI, I have also replaced the air filter, spark plugs, and fuel filter to no avail. The fuel pump is mechanical, so I wouldn't think it is heat sensitive and this sure seems to be a heat issue of some sort.
So....hopefully you can follow my confusing description and I'd sure appreciate your insight.
Thanks in advance.
James

I have the same problem and it has gotten worse. It is a fuel delivery issue for sure. I have a clear fuel filter and when the motor starts to shut down the filter is empty and bubbling. The mower is running out of fuel! When it shuts down I can see the filter fill with fuel again. When I crank it again it takes a bit for the fuel to pull into the motor and runs till the filter is empty again and starts shutting down. I suspect there is trash in the tank, fuel line and or both restricting fuel from being pulled up to the motor. What are your thoughts?

Luffydog · Sep 8, 2019

Drain the fuel out of the tank and take line apart and blow air back into the tank it sounds like it is clogged up in the tank where the fuels comes out. Take a bright light and shine inside the tank and look for debree. Give that a go and let us know how it runs afterwards. The fuel should come out of hose the same size as of the fuel line.

Frustrating Intermittent Problem with Scag Turf Tiger Koehler Engine

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