Lawn tractor hard starting

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I have a Husqvarna 48" lawn tractor with a 24 HP Briggs & Stratton engine that has been used for three seasons cutting one acre of grass. I bought it new and up until last year it always started instantly, but during the last cutting season it became very hard to start.

I changed the oil, the oil filter, the air filter, the gas filter, and the blades, cleaned the spark plugs, sprayed solvent through the air intake, and ran a couple of tanks of gas with double-dose Techron, but to no avail (I always use non-ethnaol gas). I know the battery is weak as it dies after about 15 seconds of cranking, and I'll replace it soon, but even when I jump it with my car it still takes about 15-20 seconds to start in spite of the high cranking speed.

Now here's the kicker - when it does start it runs like a champ for the 1.5 hour grass cutting. I would think that some conditions that could cause the hard starting, such as a dirty carburetor, would also affect the running. I am wondering if a crack of pin hole in the gas lines is causing the gas to drain back to the tank, requiring more cranking to prime the lines (there is not obvious leaking to the ground or gas odor). That said I would also think that line priming would be rather fast.

Any ideas I should try next?

Tom
 
It may not be choking correctly. It could be weak spark cranking.

Can you get to the carb easily? Spray just a shot of starting fluid and then crank. If it starts right up, you have a choking early fuel issue. If it's still lazy it's prolly the ignition ...

New battery and clean both ends of the ground cable. Use some silicone grease to make sure no rust under chassis end. Loosen and re-tighten at least one engine mounting bolt to get a good chassis ground. Loosen and re-tighten the bolts or screws that hold the ignition in place so that they have good return path for the spark energy.

What's the plug gap? Are you using fine wire or platinum plugs? OPE (Outdoor Power Equipment) has some of the wimpiest on the planet. They do not age well. They get internal corrosion, etc. But we put the cheapest plugs in them and expect them to work well. They are candidates for the easiest plugs to fire to help them along ...

I'd get an adjustable spark tester off eBay and see what kind of spark energy you are actually making? Then go from there
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Look for a vacuum leak on the intake system .

We have a small B&S with a plastic " tube " that functions as an intake manifold . A loose mounting bolt allowed the " tube " to vibrate until it cracked .

This produced a vacuum leak & the engine would not start until you gave it a shot of fuel . After starting , it ran OK until / unless you shut it off / let it die .

Also , my SOP each spring is to check the air filter and install a new plug . Change oil & drain / fill with new gas .
 
How does the machine idle once it's warm? If it won't idle well and if the choke system is working, I'd pull the carb to look at the low speed circuit. The slow speed jet might be obstructed. If so, it's "wire time". Elixers are good at cleaning out your wallet, not so for cleaning carbs.

If it has an engine pulse pressure fuel pump, I'd also check that. Pull the fuel line off of the carb, put the end into a jar or can and spin the engine to see how the fuel flows. Do it when the engine is cold to replicate cold starting conditions. The diaphragms in the pump might be getting weak and not priming the pump as efficiently when cold.

If any of your fuel lines had a hole, you'd definitely be smelling gas.

Once the fuel system has been ruled out, I'd look at the electrics. Try a couple new plugs first. If you have healthy spark on both leads, the next step would be to look at valve clearance.

Let us know when you get it figured out.
 
This model does not have a manual choke. The choke is set automatically, but there a setting on the throttle for cold starts below something like 32°F. That said I should be able to see the choke under the filter to see if it is closed when cold. The tractor is at my farm and we'll be going there sometime next week.
 
You're doing correctly on keeping away from ethanol gas. Try this before tearing into any mechanical stuff: Add some SEAFOAM to the fuel - try 2 or 3 ounces per gallon of fuel. Stir it around if you're adding it to the fuel tank if you can. I'm a Techron fan myself, but try the Seafoam. Not Chemtool or anything else. Run it as much as possible. Repeat.

I run a John Deere 216 that has 3,000 hours (bought it new - NOT the original motor) and I think I know of what I speak.

The fact that you can run it for over an hour once it starts tells me it's a fuel delivery problem.

BTW, you HAVE cleaned the air filter, correct????

Keep us informed.
 
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One thing I forgot to mention was checking pulse pressure line from then engine to the fuel pump. If it's leaking or not well connected, that could be a contributing factor.
 
Vacuum leak, water in the gas and bottom of fuel bowl, dirty carb replace or clean in an ultrasonic cleaner. Seafoam is great.
 
I think that with only 3 years mowing a 1+ acre that the hours are probably less than 150 so I think it is not intake/exhaust valve settings. In addition; it sounds like the maintenance is very good so as suggested, fuel delivery could be the problem. I think the choke system or pulsed fuel pump could be the issue. Ed
 
Tom NJ,
I have a 6 year old B&S with the 21HP engine. Mine blew the head gasket 2 years ago. Very common on B&S engines. The repair guy miss adjusted the exhaust valves and the engine became very hard to start, because the compression release is connected to the exhaust vales. Mine was only 3-4 thou over the .005 clearance and would not allow the CRS to function. Check the clearance.
 
Given that he mentioned it seems to be cranking over at a good speed, I'd suggest that looking at the valve adjustment is probably not the culprit.

We've had lots of fun with valve adjustments on another Briggs powered lawn tractor, and as mentioned, the compression release tied to the valves being adjusted correctly. When the valves are out of adjustment, the engine will generally barely crank once the compression won't release...

Stick to looking at the fuel delivery in particular.
 
Next time it won't start, take the gas cap off. My JD lawn tractor was doing exactly what you describe. The gas cap venting became clogged because of whatever. I made all the vent holes just a tad bigger. Never had a problem after that.
 
If it were the gas cap venting, chances are that it wouldn't be able to run at high rpms very long due to creating a vacuum in the fuel tank. I doubt that is the problem in this instance.
 
Originally Posted By: MNgopher

We've had lots of fun with valve adjustments on another Briggs powered lawn tractor, and as mentioned, the compression release tied to the valves being adjusted correctly. When the valves are out of adjustment, the engine will generally barely crank once the compression won't release...

This is important; it will make you think that the battery is weak when it is not. The engine will crank part of a turn then stop.

Test for fuel delivery is to remove the air cleaner and drop a little starting fluid or gasoline into the intake, then crank. If it starts (or tries to) right away, there is a problem with lack of fuel or not choking.

If the idle jets are clogged it will be hard to start. When you pull the throttle control on the dashboard all the way to slow, it should idle smoothly without surging. You should also be able to hold the throttle lever on the carb against the screw stop and have it maintain a smooth idle without stalling.
 
NEVER jump start OPE and motorsports from a RUNNING car or truck, BTW.

A running vehicle is usually 14.5 volts -
that will kill the voltage regulator on the charging system of OPE/ATV's almost instantly
 
When it started, it ran fine. Later found the gas tank was sucked in to where it bent the plastic and stayed that way. I was squirting gas in the carb to get it to start.
 
My brother works on B and S a lot. The float valve has a tendency to leak, flooding the motor. Does it puff black smoke upon starting? Would indicate a rich condition.

Use some common sense to solve the riddle. Next start, spray in some starting fluid first. If it pops off, its too lean and probably a choke not closing OR air leaking somewhere (doubtful or it would not run well once started). Once you determine if it is rich or lean, drill down on causes accordingly.

My bet is it's a rich condition and the 15 seconds cranking is slowly clearing out the excess gas.
 
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