Starting issues

JBob · May 30, 2013

I have a Grasshopper zero turn mower with a Kubota 25 HP diesel engine. I'm finding that through the past couple months I am having to push the throttle up to get it to start. It is getting worse as mowing season goes on. Right now I'm having to go to nearly half way throttle before it will start.

Once it starts I can pull it all the way back down for a smooth idle. Engine runs great once started. I've changed all fuel and air filters. Fuel is fresh and clean. I'm running the same fuel in my tractor with no issues. It does have glow plugs and I do use them. I'm assuming they are working. Not sure how to tell. There is a substantial amount of black smoke that rolls out when it starts with throttle up. I'm thinking fuel issue but not sure how to diagnose.

Any suggestions appreciated.

Blaneypark · May 30, 2013

Could have dirty injectors. Get some "Power Service" and put the correct amount in the fuel tank and keep on doing that. I use that year round in my Grasshopper, or any other diesel engines i have.

moretzb · May 30, 2013

I would check the glow plugs. They are simple heaters and can usually be checked with an ohm meter. A quick web search will find some directions I am sure. Hope that helps.

Grandad4 · May 30, 2013

I'm no expert on diesels but I have a couple of Kubota diesels, so take these thoughts for what they are worth. First, the black smoke is definitely not normal... you've probably already concluded that.

Next, about the glow plugs. With my equipment, they heat temporarily and then turn off. If you turn the key so the glow plugs go through their heat cycle 2 or 3 times before you crank it, it should start instantly even at idle because it raises the cylinder temperature higher than only a single heat cycle. If it doesn't make any difference and you still have to give it more throttle to start, I'd be re-thinking the "I'm assuming they are working" comment about the glow plugs.

If you had fuel problems, it wouldn't make sense for the engine to run perfectly once it starts. I've heard others describe removing the injectors to visually confirm they are indeed supplying fuel, but I've never had to do that. Maybe someone with more knowledge will have more/better advice.

Hope you get it resolved.

Egon · May 30, 2013

Have you checked out the throttle linkage ajustments for any change?

JBob · May 30, 2013

Egon said:
Have you checked out the throttle linkage ajustments for any change?

I considered that but once it starts the linkage appears correct. It requires the throttle to be pulled all the way back to obtain low idle. As soon as I bump it up any it starts to rev up. I do think this needs to be verified. Thanks for the suggestion.

JBob · May 31, 2013

moretzb said:
I would check the glow plugs. They are simple heaters and can usually be checked with an ohm meter. A quick web search will find some directions I am sure. Hope that helps.

It's a glow plug issue. Found one bad. Thanks for the input. Saved me some money at the dealer.