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#4688668 - 03/08/18 11:59 AM Lawn tractor hard starting
Tom NJ Offline

Registered: 07/27/06
Posts: 2129
Loc: Virginia
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?


#4688678 - 03/08/18 12:07 PM Re: Lawn tractor hard starting [Re: Tom NJ]
BrocLuno Offline

Registered: 09/06/15
Posts: 5625
Loc: Kalifornia Kollective
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 smile

Edited by BrocLuno (03/08/18 12:14 PM)
Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.

#4688683 - 03/08/18 12:14 PM Re: Lawn tractor hard starting [Re: Tom NJ]
Squirrelee Offline

Registered: 09/11/11
Posts: 90
Loc: Ol' Kentuck

Edited by Squirrelee (03/08/18 12:17 PM)
Some guy's dog thinks I'm a good man.

#4688689 - 03/08/18 12:20 PM Re: Lawn tractor hard starting [Re: Squirrelee]
GravelRoad Offline

Registered: 05/30/15
Posts: 170
Loc: Virginia
Yes, check choke adjustment. We see this a lot on Husqvarnas with manual choke on B&S V-Twins. New and used.
2016 Subaru Outback Premium. PUP or PP 5w30 oem filter
2013 Hyundai Elantra loaded. lifetime free oil/filter change

#4688692 - 03/08/18 12:25 PM Re: Lawn tractor hard starting [Re: Tom NJ]
BrocLuno Offline

Registered: 09/06/15
Posts: 5625
Loc: Kalifornia Kollective
Yeah, a valve adjustment may help too. Run them a wee bit on the loose side. More TQ and better valve cooling. It's not a NASCAR engine smile
Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.

#4688713 - 03/08/18 12:55 PM Re: Lawn tractor hard starting [Re: Tom NJ]
WyrTwister Offline

Registered: 01/13/13
Posts: 1586
Loc: Texas
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 .
God bless

#4688718 - 03/08/18 01:00 PM Re: Lawn tractor hard starting [Re: Tom NJ]
boraticus Offline

Registered: 04/19/09
Posts: 2932
Loc: Canada
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.

#4688724 - 03/08/18 01:03 PM Re: Lawn tractor hard starting [Re: Tom NJ]
Tom NJ Offline

Registered: 07/27/06
Posts: 2129
Loc: Virginia
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 32F. 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.

#4688739 - 03/08/18 01:25 PM Re: Lawn tractor hard starting [Re: Tom NJ]
David2431 Offline

Registered: 01/28/18
Posts: 55
Loc: Missouri
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.

Edited by David2431 (03/08/18 01:27 PM)

#4688755 - 03/08/18 01:51 PM Re: Lawn tractor hard starting [Re: Tom NJ]
boraticus Offline

Registered: 04/19/09
Posts: 2932
Loc: Canada
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.

#4688759 - 03/08/18 01:53 PM Re: Lawn tractor hard starting [Re: Tom NJ]
JLawrence08648 Offline

Registered: 01/20/17
Posts: 259
Loc: NJ
Vacuum leak, water in the gas and bottom of fuel bowl, dirty carb replace or clean in an ultrasonic cleaner. Seafoam is great.

#4688780 - 03/08/18 02:23 PM Re: Lawn tractor hard starting [Re: Tom NJ]
Eddie Offline

Registered: 12/07/03
Posts: 9658
Loc: Florida, Cape Coral
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
CX5 Touring 2.5L :-)

#4688841 - 03/08/18 03:21 PM Re: Lawn tractor hard starting [Re: Tom NJ]
tig1 Online   content

Registered: 01/03/09
Posts: 13726
Loc: Illinois
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.
2007 Ford Fusion 228,000 miles
M1 0-20 EP
2017 Ford Fusion 52K
M1 0-20 EP
10,000 mile OCIs on both engines
M1 ATF and MC LV
M1 10-30 in all OPE
MC filters

#4688849 - 03/08/18 03:27 PM Re: Lawn tractor hard starting [Re: Tom NJ]
MNgopher Offline

Registered: 09/17/02
Posts: 4069
Loc: Lakeville, MN
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.

#4688852 - 03/08/18 03:30 PM Re: Lawn tractor hard starting [Re: Tom NJ]
oldhp Offline

Registered: 06/28/12
Posts: 1658
Loc: USA
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.

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