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B&S Engine won't stay running


AndyK's Avatar
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09-12-09, 06:38 AM   #1  
B&S Engine won't stay running

B&S 15 hp Model 28N707, starts, runs fine for about 30 minutes, then starts sputtering, and dies. Will start up again, but the same thing happens. Will run at about 90% of full throttle just fine, but when moved to full throttle, it begins surging and dies. I've replaced the fuel filter, spark plug, air filter, and positive battery cable. Any thoughts? Thanks

 
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09-12-09, 08:38 AM   #2  
Check to see if the ignition module/armature is producing spark when engine dies. This can be done by installing an inexpensive inline spark tester to see if ignition is taking place when engine quits. If no spark, the ignition module/armature is the problem.

This year I have had a dozen or so riding mowers in my shop with a problem as you describe. The ignition modules were OK. I found the fuel lines damaged from ethanol mix gasoline. The damage is internal to the fuel line and cannot be seen externally. You can feel the line and may find hard and soft spots indicating deterioration. When you open these fuel lines, you see swollen material restricting fuel flow.

If fuel lines are the problem, replace ALL fuel lines. Replace with a methanol resistant fuel line.

 
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09-18-09, 12:57 PM   #3  
B&S Engine won't stay running - thanks Airman

Airman, thanks for the help. I tried your second suggestion first and replaced the fuel lines with automotive fuel lines. Began mowing my yard today and made it about 20 minutes before the same problem appeared. What should I replace next? Should I get the spark tester or just replace the Armature (I'll need to look at the manual to determine what this is.) Thanks so much for the help.

 
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09-18-09, 02:12 PM   #4  
In addition to the model number of your engine please post the TYPE number.

The surging does sound fuel related but could be ignition related. Does your engine use a fuel pump?

Yes, get an in-line spark tester. Install it and operate the mower. When the engine quits observe for spark as engine dies or while attempting to start.

Testers like the one in the link below are what I like best. They are easy to see. You may find one at an auto parts store.

Tool Aid 23900 In-Line Ignition Spark Checker

 
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09-18-09, 03:16 PM   #5  
B&S Engine won't stay running - thanks Airman

On the way to the auto parts store to get the in-line ignition spark checker. The information on the motor is: B&S, Model 28N707, Type 1118E5, Code 0108167D.

 
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09-18-09, 06:38 PM   #6  
Try loosening the gas cap when it starts surging and see if the problem persists.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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09-19-09, 08:33 AM   #7  
Andyk.....Don't go buy anything else to test the firing of this engine. You have a fuel problem. Most probably trash in the carb, fuel line or tank. These engines have an eletronic ignition so it will either have a spark or it won't. There is no in between unless you have a safety switch shorting out on the seat or deck.
The first thing I would try is a good carb cleaner. I use Chemtool. You can buy it at most any auto parts store for a few bucks. If the trash can be desolved this will do it. If not you'll need to check through the fuel system from tank through the carb to find the trash. It is also possible that you have water in the fuel. In which case you'll need to drain the old fuel, replace it with new fuel and add the chemtool to help dry the rest of the moisture from the system. If you can't find the chemtool, seafoam will also work. Good luck..

 
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09-19-09, 01:37 PM   #8  
Posted By: needhelp123 Andyk.....Don't go buy anything else to test the firing of this engine. You have a fuel problem. Most probably trash in the carb, fuel line or tank. These engines have an eletronic ignition so it will either have a spark or it won't. There is no in between unless you have a safety switch shorting out on the seat or deck.
The first thing I would try is a good carb cleaner. I use Chemtool. You can buy it at most any auto parts store for a few bucks. If the trash can be desolved this will do it. If not you'll need to check through the fuel system from tank through the carb to find the trash. It is also possible that you have water in the fuel. In which case you'll need to drain the old fuel, replace it with new fuel and add the chemtool to help dry the rest of the moisture from the system. If you can't find the chemtool, seafoam will also work. Good luck..
Actually it is fairly common for defective electronic ignition coils to fail when they are hot but work normal for periods of time after cooling. I wish I had a nickel for everyone I have seen.

My advice is just a step in the process of elimination.

Here is part of what Briggs and Stratton has to say on the subject:

"As coil temperature can aggravate minor coil imperfections that normally wouldn't be a factor, the same test can be done on a warm engine. Engine quits while running? Hook the tester up in line with the spark plug and start the engine. When the engine quits, monitor the window. If spark is present, the problem is not in your ignition coil. By the way, this test stresses the coil well beyond the demand it would see in operation. Think about it. We're asking the coil to build enough voltage to jump TWO gaps - the tester as well as the plug. If your engine starts and runs OK cold and hot, you've got a healthy ignition coil."


Read about Ignition System Theory and Testing at this link:

How does the Magnetron Ignition System function? How can it be tested?

 
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09-20-09, 08:30 AM   #9  
B&S Engine won't stay running

Thanks for the help with this. Couldn't find the spark tester at several auto parts stores, so I'll order one through the internet. Mowed my yard Friday afternoon when it was about 80 degrees here and the problem was apparent. Mowed it again Saturday morning wanting to see if loosing the gas cap would help, but since the temperature was only about 65 degrees, the mower never acted up. I'm ordering the spark tester and will also try the Chemtool. Both won't cost that much and both will help run this into a corner. THANKS AGAIN TO EVERYONE FOR THE HELP.

 
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09-23-09, 05:05 PM   #10  
B&S Engine won't stay running

Got some Seafoam and put in about 3 oz in two gallons of gas. Mowed yard, same problem. Should I mow it again to let more of the solution pass through the carb?? Dump more Seafoam in the gas? Haven't got the spark tester yet.

Thanks

 
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10-06-09, 09:43 AM   #11  
B&S engine won't stay running - update

So I've used the Seafoam and the problem persisted. I took apart the carb and found a hair or something like a paint brush bristle in there, but the problem didn't go away. I got the ingnition tester, mowed the yard with the testor installed, and the problem didn't appear. It is however much cooler here now so I'm wondering if the ignition coil is not getting hot enough to show the problem? Any thoughts? THANKS

 
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