Briggs Engine starts, runs, then dies

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  #1  
Old 04-03-07, 07:24 PM
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Briggs Engine starts, runs, then dies

Howdy,

I have recently acquired a Craftsman mower with a 15.5 hp Briggs engine (28N707) that had been sitting for a few years. The previous owner started it for me by pouring gas in the breather and it cranked and ran for about a second or so. My initial guess was the carb solenoid was fouled - I pulled it and it was, so I cleaned it as best I could with some carb cleaner and a brush so I could at least rule that out as the culprit. I replaced the spark plug and the in-line fuel filter as well.

The maiden crank was positive (although I did have to jump it from the truck) and ran strong for about 5 seconds and then it started missing. Once it started missing, it ran for progressively shorter periods until it completely died, running for about 20 - 25 seconds total After letting the battery charge up again, the same thing happened, except it ran for about 3 seconds and then repeated the previous scenario. At this point, it seems like it will run almost every time I turn it over, but only for one to two seconds before dying. Every once in a while, it will "pop" like a backfire, but will crank and run for a a second the next time I turn the motor over.

It's been so long since I've fooled with an engine, I don't even know where to begin. Does anybody have any ideas where to begin to tackle this beast?

Thanks in advance.
 
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  #2  
Old 04-03-07, 09:30 PM
Azis
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For troubleshooting the fuel system with a solenoid, I use a like threaded bolt in place of the solenoid. I think yours is still a standard thread. You can match it up by finding a nut to fit the solenoid at your hardware store then use the thread size and pitch for a like bolt.
You may be able to test yours if it has two wires. Remove it and watch listen and feel as you turn the key to on, it should activate and suck the plunger in. Try it a few times and see if every time its sharp and quick.
If this solves the problem by chance then it could still be just a loose or poor ground elsewhere in the circuit.
 
  #3  
Old 04-04-07, 06:14 PM
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The solenoid is working correctly - I tested it at the office with at benchtop power supply and there seems to be no problem with it now. With all the fouling that I cleaned off it (black and very gummy), I suspect that there may be more further up in the carb.

I'd like to check for more fouling further up in the carb, but can't for the life of me figure out how to remove the bowl, any suggestions? The engine is a 28N707.
 
  #4  
Old 04-04-07, 06:42 PM
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Which Carburetor is on your engine???

Nikki or Walbro carburetor?

If it's a Walbro then the bowl will come of after the solenoid is removed. You might have to pry on it a little as it could be stuck to the bowl gasket and or gum and varnish may be causing it to stick as well.

For the Nikki carburetor there are two (2) retaining screws on the bowl that must be removed in order to take off the float bowl, in either case it's easier if you remove the carburetor from the intake manifold first.

Chances are if the solenoid had a lot of gunk on it, then there is more on the inside of the carburetor.

Best of Luck....
 
  #5  
Old 04-05-07, 02:27 AM
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Post back with the engines' type and code numbers and we can provide you with the correct carburetor rebuild kit part number. You'll want to remove the carb, soak it in a bath cleaner and install the carb kit.
 
  #6  
Old 04-05-07, 08:11 PM
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The engine code I have, as looked up by a Sears employee is 28N707-0173-01. Is this all of the code, or is there more to it?
 
  #7  
Old 04-06-07, 06:50 AM
Azis
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There is one last part of the engine #, an 8 digit date code.
It would be good to confirm, but if you have removed the solenoid and still can't get the bowl off, you likely have the Nikki carb with the two retaining screws Tech mentioned. The carb should also be marked with "Nikki"

If you do have the Nikki, the overhaul kit is part #695427 gasket set is #695428
If you do have the Walbro carb, the date code from the engine will be needed to determine the correct kit.
Bench testing the solenoid is good, however it will not completely illiminate it as the problem. The circuit could have a bad ground or the plunger may not operate as well under installed conditions, IE: full of fuel.
Since you found it gunked up, it is likely its not an issue, but good to keep in mind.
 
  #8  
Old 04-12-07, 04:48 PM
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Got a carb rebuild kit - have questions

The engine has a Walbro carb (the bowl was really stuck on), Briggs P/N 698620.

I checked the solenoid out of the bowl, and it fired, but very sluggishly so I replaced it and that seems to have solved part of the problem. After hosing the carb with carb cleaning spray, the engine started (with some gas down the breather) and ran for about 1.5 to 2 minutes before dying.

I pulled the carb this afternoon and completely disassembled it, and the inlet needle was so fouled it wouldn't budge, so much so that I cracked the float getting it out (doh!). While waiting on the new float to arrive, I'm left with two things to remove from the carb body: the emulsion tube and the needle seat.

The tube seems to be awfully tight, and I've already scuffed the edges of the drive slot, so I'm a little gunshy about getting forceful with it given my blunder with the float - any tips on how to get it out without any causing any further problems? Secondly, I can't figure for the life of me how to get the inlet needle seat out - any ideas?
 
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Old 04-12-07, 07:45 PM
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I wouldn't reccomend trying to remove the tube if it's that tight, and already damaged a bit. I suggest soaking the carb in a bath type carb cleaner, which should clean out the tube without having to remove it.

Does your carb have a rubber needle seat? If so, you can pluck it out with a thin pick or turn a wood screw into it just enough to grab it and pull it out. Don't let the screw or pick damage the brass inlet. Some of these carbs have rubber tipped needles, and the seat is solid brass...not a normally replaced part.
 
  #10  
Old 04-13-07, 09:23 AM
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The tube wasn't damaged much, but after soaking in some cleaner, it came right out. I'm going to replace it with the new one from the rebuild kit in any case.

The needle seat is brass, and there's no rubber component to it, that I can see. I was under the impression that it was replaceable because a replacement came with the rebuild kit, and it lists pressing in a new one in the B&S carb rebuild guide on the B&S website. I'll leave it alone and just clean it up as best I can.

Anything else I should watch out for when I start putting this thing back together?

Thanks for all the help!
 
  #11  
Old 04-13-07, 10:27 AM
Azis
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The rubber component is on the needle itself. The seat being brass and the needle tip being softer rubber, the needle tip may wear but the brass seat should not.
The kit may also come with welch plugs, which I have rarely heard of being removed and replaced. I have not myself as the need has not arisen.
 
  #12  
Old 04-14-07, 09:46 AM
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I got the carb put back together - haven't been able to test it due to a dead battery, BUT there's something else afoot.

I checked the oil this morning before trying to jump start it and the oil level has gone UP since I changed it last week. I pulled the case drain plug and it was full of gas. This had to have happened before I pulled the carb to rebuild, and after I replaced the solenoid. This one stumps me... maybe the new solenoid isn't seating?
 
  #13  
Old 04-14-07, 11:32 AM
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The gas in the oil is or was caused by a leaking needle in the carb. Your reconditioning of the carb should have solved the problem.
 
  #14  
Old 04-14-07, 04:42 PM
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I got a fresh battery and the engine cranked up without any hesitation and ran fine for several minutes. I killed it and restarted it a few times more, and everything seems to finally be in order with it. I appreciate the advice you folks have offered - it has really helped.

There's one more issue that popped up after I got it running - it seems that one of the safety interlock switches is not working correctly. When the pedal is fully engaged, it will start and continue to run, but dies when disengaged. I bypassed the seat switch while working on the engine for convenience, so I'm thinking it's the PTO switch. Any advice on how to troubleshoot this problem? The mower's model number is 917.256524.

Thanks!
 

Last edited by texagg98; 04-14-07 at 05:04 PM.
  #15  
Old 04-14-07, 06:26 PM
Azis
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Your seat switch is not bypassed and I bet the fault with the circuit. If you have the parking brake on, the circuit bypasses the seat switch. If the PTO switch shows engaged the engine will not crank even with the brake on.
Plug the switch in or replace it.
 
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