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View Full Version : 1990 Kohler Magnum 18. Fuel starved


jeffbond001
07-26-2011, 02:28 PM
New at this so any info and help will surely be appreciated. I have a 1990 Kohler magnum twin engine on a Snapper lawn tractor. First of this mowing season it starts sputtering and dies after about 30 min or so of use. Slightly bumpy slightly hilly yard. Had carb rebuilt, put new fuel lines on completely, cleaned tank, put on clear type fuel filter. When cold has plenty of fuel in filter, then when starts sputtering filter is nearly dry. Pull choke to keep it running to get back to garage. Originally thought it was vapor locking so drilled a small hole in middle of gas cap and can easily blow air both ways through cap. Pull line from fuel pump and gas flows freely from tank through filter, so to me this means no clogged lines or filter. Starts fine after a few hours or the next morning, then back to same sputtering cycle. Only other thing I can think of is, will a fuel pump stop pumping after it gets warm? Any suggestions will be greatly appreciated. I already have no hair so nothing to pull out or do in frustration, lol. Thanks in advance. Jeff

piston slapper
07-26-2011, 02:34 PM
Is the gas tank higher than the carb?
If so, bypass the fuel pump, run the fuel line directly to the carb. (gravity feed)

jeffbond001
07-26-2011, 02:38 PM
Piston, not really. almost level with the fuel drain on the bottom of the tank. So I dont think it would flow well. Thanks though.

piston slapper
07-26-2011, 03:33 PM
Piston, not really. almost level with the fuel drain on the bottom of the tank. So I dont think it would flow well. Thanks though.

If its almost level with the drain, bypass the pump , Fill the tank and see if you can run for longer than 1/2 hour. Its cheaper than replacing the fuel pump, especially if its not bad.

topsites
07-26-2011, 10:46 PM
Nope, the fuel supply was not a bad path to pursue but I believe at this point we have eliminated it as a possible cause,
way things are sounding your fuel supply is healthy so now I'm leaning towards saying it's the ignition coil(s) that like to
act up like that when things warm up, being that it's a V it could be either or both but that would be my next guess.

jeffbond001
07-27-2011, 09:08 AM
Topsite, I definately agree with it could be and ignition coil, the only thing that gets me is that when it starts sputtering and nearly dies, I can pull the choke and it will continue running fairly well with the pto off, enough to get me back to the garage. Is the choke not compensating for being fuel starved. If the coil starts cutting out, would the choke have anything to do with it? Thanks for your advice. Jeff

jeffbond001
07-27-2011, 09:11 AM
Piston, the carb intake is just a tad higher than the outlet on the tank, so it didn't flow enough to run. Any more suggestions. Thanks.

topsites
07-27-2011, 09:15 AM
It's between that and I'm thinking the carburetor rebuild may not have done the trick, I wouldn't be too fast
to place blame, it's just one of those things to do with carburetors, rebuilds don't always work.

On another note how's compression looking?
You might test that right quick just to be sure we don't have a problem that's been completely overlooked.

Fact is I can remember playing around with one of my trimmers when it had a bad coil and choking may or may not
have helped but with a bad coil the choke might just keep it from dying completely, I can't recall for sure if choke and coil
works or how it keeps the engine from crapping out but the problem now is one of cost...

You are probably going to have to spend between $50 to $80 on a part and then again maybe...
Either buy a new carburetor and replace it.
Or buy a coil and replace either one, then if that doesn't help it's the other...

Once you purchase either part there's that chance you still have to buy more, the absolute worst case scenario would
be that you have to buy all three (as in two coils and a carburetor).

I also believe that on a carbureted lawn mower engine there is no fuel pump, it's all gravity feed so we can probably eliminate that.
I would probably go the carburetor route first, buy a brand new one.
Mostly because there's only one of those to replace, rebuilds don't always work, and it fits the choke scenario.

Beyond that we need to ask Restrorob lol

piston slapper
07-27-2011, 03:14 PM
Piston, the carb intake is just a tad higher than the outlet on the tank, so it didn't flow enough to run. Any more suggestions. Thanks.

Is the outlet on the bottom of the tank? Seems to me that if the carb inlet , and the tank outlet were within an inch of each other, When you filled the tank, the fuel level would be much higher than the carb. If this is the case, and it wont flow fuel, either your fuel line is kinked or clogged, or the screen in the tank has an obstruction.

piston slapper
07-27-2011, 03:35 PM
It's between that and I'm thinking the carburetor rebuild may not have done the trick, I wouldn't be too fast
to place blame, it's just one of those things to do with carburetors, rebuilds don't always work.

On another note how's compression looking?
You might test that right quick just to be sure we don't have a problem that's been completely overlooked.

Fact is I can remember playing around with one of my trimmers when it had a bad coil and choking may or may not
have helped but with a bad coil the choke might just keep it from dying completely, I can't recall for sure if choke and coil
works or how it keeps the engine from crapping out but the problem now is one of cost...

You are probably going to have to spend between $50 to $80 on a part and then again maybe...
Either buy a new carburetor and replace it.
Or buy a coil and replace either one, then if that doesn't help it's the other...

Once you purchase either part there's that chance you still have to buy more, the absolute worst case scenario would
be that you have to buy all three (as in two coils and a carburetor).

I also believe that on a carbureted lawn mower engine there is no fuel pump, it's all gravity feed so we can probably eliminate that.
I would probably go the carburetor route first, buy a brand new one.
Mostly because there's only one of those to replace, rebuilds don't always work, and it fits the choke scenario.

Beyond that we need to ask Restrorob lol

Its gonna take more than RestroRob to correct all the mistakes in this post alone.
For starters ....(not talking about the thing that starts the engine)
A kohler Magnum is not a V twin ...its an opposed twin
This "carbureted" engine has a fuel pump
TOO MUCH TO CORRECT,,...Help me out RR

jeffbond001
07-28-2011, 08:32 AM
YeeHawww, got her fixed. Took a chance and bought the $82.00 fuel pump, put her on, cleaned all the fins on the engine under the covers I had to remove (didn't really help in this problem but I couldnt believe how dirty they were), put her back together and the Ole Snapper is running like the day my Dad bought her brand new! This is a real machine, cuts so smooth, makes my yard look like a golf course, so needless to say I am very glad to get her going again. I have about 3 acres to cut and it was sure needing it! Thanks for all the info guys. I'll definately keep looking through this forum for other tips and tricks. Jeff Bond

Tact
07-30-2011, 10:43 AM
I have a very similar problem with my Cub Cadet with a Kawasaki FH721V engine. Mine works fine when cold but when it warms up and it is put under a load it will try to die right there in the yard, like it's starving for fuel or there is a electrical breakdown.

If I back up when it tries to die, the engine will catch it's breath and run fine until it is put under a load again.

I was thinking one of the coils was going bad, or both. Then I read this thread now thinking it might be the pump. But what I can't understand is how the pump would start to malfunction only when it gets warm.

I also thought about the governor adjustment, but again, the engine runs fine when cold.