Briggs 16HP Vanguard on Sabre 1642HS won't start

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  #1  
Old 11-18-13, 08:46 PM
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Briggs 16HP Vanguard on Sabre 1642HS won't start

I've been having problems getting my John Deere Sabre (1642HS w/ Briggs 16HP Vanguard engine) to start for several months now, but normally if I just persist, play with the choke, etc., it'll get going, then run fine, seemingly at full power for a good 40m or so.

Usually, I can even shut it off during the mowing, let it sit for a minute or two (while doing something else) and it'll start right up again.

My battery is a little weak and probably about in need of replacing, and sometimes when I try to start, it'll turn over very sluggishly for awhile, then sometimes somehow change and crank really hard for awhile. Usually, I can get it started within a few minutes even if it's pretty cold out (40 - 50 degrees maybe).

The past couple of days, however, I've not been able to get it to start at all, so I think whatever problem has been festering is now worse.

I noticed my air filter was getting wet, I assume with gas, so I researched that a bit and heard that the needle valve on the carb float might be sticking. So I took the float bowl off, and loaded up the parts that were exposed with carb cleaner. It looked very clean, and the operation of the float seemed very smooth and non-sticky to me.

When I put it all back together, it behaved badly still. I got several cranks on it, but no sound of firing at all. When I pulled the plug and cranked, I got zapped a bit, so I think the spark is fine.

Also, the plug is a little black on the end, but not seriously fouled. I think I've been flooding it pretty hard with all of these cranks, and I wonder if that's a symptom of the real cause.

When I take the filter off, and can see what I think is the breather hose connected to the crankcase, after I've cranked for awhile, I see fuel back up in the carb and see what I assume is gas spraying out of this breather hose!

I think that's the main (only?) way I was getting gas into the filter in the first place.

Oh also, I did replace the filter with a brand new one thinking maybe that was the cause, and now I'm thinking that was probably unnecessary.

So, I'm kind of stuck at this point -- anyone have some more diagnoses for me to try or think they know exactly what my problem is?

Thanks!
 
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Old 11-19-13, 04:31 AM
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Take the carburetor completely off and disassemble and clean it with the carburetor cleaner.
Ethanol fuel is the cause of most fuel system failures. It destroys fuel lines, and gaskets.
Try to find a place that sells non ethanol fuel, your local power equipment deal or marina will know where to get it.
Short of that buy some additive to counter act the effects of it.
 
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Old 11-19-13, 06:27 AM
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It sounds like you may have a leaking inlet needle on your carb. During storage the fuel leaks through and gets into the intake and floods the engine when you are trying to start it. Usually the symptom is many, many cranks before it starts. Occasionally the cranks can get held up by a form of hydrolocking of the fuel. In any event, if you do not have a manual fuel shut off valve on the mower you should install one between the tank and the fuel filter. Most likely this will resolve the problem and it is only a $10 and a 15 minute fix, however the optimum fix is this shut off valve installation as well as a carb overhaul to fix the needle. If that leak gets larger and larger it may flood it when it is running and then you will have no choice but to rebuild the carb.

2ndly. If I am right, a lot of that leaking fuel has now made its way to the crankcase, diluting your lubrication. If the shut off valve works, your very next move is to change the oil in the crankcase.
 
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Old 11-19-13, 07:44 AM
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Thanks for the replies guys. I have heard the advice about installing a fuel shut off and am not necessarily opposed to that, though if my anti-backfire solenoid is functioning properly, there should be no need for one (to stop flooding of the carb), right?

I'm talking about a solenoid like this, that screws on to the bottom of the bowl:

694393 Fuel Solenoid Briggs Stratton w Walbro Carb | eBay

Also, once I get my starting problem fixed, I do plan to change out the oil, just in case.
 
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Old 11-19-13, 08:18 AM
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Those solenoids will not stop the leak. I forget exactly what they do but I know from personal experience that they will not stop the fuel from flowing through a leaking inlet needle.

Obviously your leak is not that large since the mower doesn't seem to flood itself when you finally get it going. I have had the same problem that you have, with the exact same symptoms and the shut off valve resolved it...and my solenoid did not do anything to relieve the problem.

To run a flooding test, you could take out the spark plug and crank over the engine 10 times or so. Put the plug back in and start it quickly. It should start better, since you blew out all the extra fuel. If it doesn't, then perhaps I am wrong.

In any event, a $10 part, readily available, will not hurt, even if your problem is something else.
 
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Old 11-19-13, 11:20 AM
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Take the bowl off and remove the needle and check in the area where the needle seals for debris. Clean the needle tip as well. You might have the carb with the white plastic insert. If so, pull it out and replace the o-ring around the needle opening. This is where the problem usually lies with those carbs, not the needle. The shutoff solenoid closes the main jet. That doesn't stop the carb from overflowing into the intake though if the fuel level gets too high. I am betting that you have gas in the oil too, so check and see if your oil smells like gas. If so, change the oil and oil filter (if your model has an oil filter) before using it. Any time an air filter gets wet, it's time to replace it, so you did good.

A model number for the engine would help, since a vanguard 16 hp could be a regular briggs single cylinder engine or it could be a japanese twin cylinder engine, very different from each other.
 
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