# briggs and stratton engine change nightmare



## ajamieb (Jun 15, 2014)

hello all im here hoping to glean some knowledge and or advice that can wake me up from the night mare i am in. i apologize in advance that this post may get long. ill try to stick to the relevant info.
last year i hit a hidden tree stump with my john deere 's mower blade while cutting. the engine stopped instantly. tried to restart, no compression. assumed sheared crank pin. no such luck, something internal. some rainy day ill open it up to examine. it was a b&s 17.5 with 695 hard but loving hours.
got a new engine (b&s 17.5) installed it, put fresh gas in the tank and cranked it up. I was quite pleased it sounded awesome.
the next day i went to take it into the back yard. my house is situated on a hill. the only way to the back is down the road a few thousand feet and through a trail in the woods. She ran and drove great for about fifteen minutes then died in the woods. I determined no fuel to the carb i thought the line from the tank was clogged. i attached a funnel to a hose and clamped it to the carb. it ran great. i kept the funnel full and rode back to the house, at the house i saw that fuel was now pouring freely from the tank line and the engine ran well when i hooked it up. it took several more stallings to realize the problem only occurred on an incline. i tried different style filters with different micron ratings moved the lines to different positions nothing worked. the old engine never had any difficulty on the hills. i thought my only option was to install an auxiliary tank above the carb that i would switch on when needed. 
heres the embarrassing part.. i had a look at the old engine and noticed a small black disk with three lines. I learned it was a pulse pump and got very excited. i installed it and the tractor climbed and mowed the hills perfectly. i went to put it in the shed after about an hour of use. it backfired and died. the plug completely fouled with a very oily fuel. I thought maybe needle valve maybe wrong carb for pulse pump application (had to change dipstick tube to install pump, thats where the vacuum port is located) so my solution was to switch to the old engine carb which direct fit. i noticed maybe the linkage was not adjusted properly. when in the wrong position the engine ran rough and the choke didnt fully close. I started it up and mowed the back lawn. Perfect. went to put it in the shed and the surging backfiring loss of power began. pulled the plug soaked with oily gas. i walked away. came back later no crank. thought the battery died. hooked up the charger came back later still dead. but not really. hydrostatic lock up. cylinder filled with fuel, a lot of fuel. 
research points to needle and seat. took apart the newer carb which also flooded the engine and found it was pristine and did not appear to be defective.
both carbs ran about an hour before the problems began. now my head is swimming. does anyone have advise where to begin? Im stumped (which is funny because it was a stump that started this whole journey) looking forward to any response. thanks. ps i changed the fouled up oil and plug after each flooding.


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## jhngardner367 (Apr 5, 2011)

Welcome to the forum !
Since you are working on a hill,I'm going to presume that you are going down hill,forward.
Depending on how steep the hill is,and how long the tractor points downhill, the engine could get oil into the cylinder,and the float could unseat,and let fuel flood the engine.
Check the crankcase,and see if the oi level is high,and check for fuel in the oil.
Avoid running downhill for long periods,and check the float level to make sure it is not too high.


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## ajamieb (Jun 15, 2014)

good thoughts about hill riding JHN. the way the hill flows i kind of zig zag around never really going down or up the steep parts for more than a few minutes i guess it is possible that the incline can unseat the valve but this tractor has been riding and mowing that hill for years without incident. both the old and the new carbs have floats that are not adjustable. last night the entire cylinder was filled with raw gas. im compulsive oil checker and until the floods, the level was correct. today my plan of attack is to change the oil and switch back to the carb the engine came with. ive been searching the web for other causes of that much fuel dumping into the engine other than float valves and could not find any. i would try a third carb but something is telling me its too much of a coincidence that two working carbs suddenly went bad.


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## jhngardner367 (Apr 5, 2011)

Does that engine have the vacuum operated fuel pump ? If so,it may have a bad diaphragm,or spring,and is letting too much fuel leak through.
Also,check the engine's crankcase breather, to see if it is dirty,or oil-soaked . That could cause a flooding condition,also......especially under load.

One other thing,and it's a long shot. Check the fuel tank cap for venting.Some have the rubber disc,and in hot weather,with a full/half tank of fuel,the disc may get sticky,and,as the heat builds,it forces fuel out of the line . Sort of like the plastic fuel cans that swell up,on hot days.


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## ajamieb (Jun 15, 2014)

hi jhn, yes the pump is the vacuum type. i suspect it too but am hesitant to buy a new one just yet. i did check the lines the vacuum line had a little oil reside but its most likely from the big gas flood yesterday. enough fuel dumped to overfill the crankcase (about a pint maybe) i already tried a new cap (because they are cheap) i was sure a new cap was the answer to all my problems but no such luck. the breather tube is still squeaky clean. 
this morning i removed the carb and inspected the needle and seat. i thought i saw a tiny speck near the hole at the center of the seat. (maybe i just wanted to see it) so i asked my wife to come down and have a look but she had no idea what she was looking at. she thought the hole which appears black under bright light was the obstruction. who knows. anyway i cleaned everything up inside and out I put the needle and float in place, put a small piece of hose on the fuel inlet and gently blew into the hose with the float raised. it held pressure. i ensured the float hinge operated smoothly and reinstalled on the motor. i know the flooding occurred while running but i thought it might be wise to install a fuel shutoff valve, i changed the oil and started it up. it seemed to be running a little rough even after warm up might be wrong but i think the exhaust sounds heavier. i only had time to test ride/mow for about 20 minutes. it had no problems climbing or descending the hills. it seemed to break up and want to stall in low idle. every once in a while it would hiccup as if the spark or fuel were suddenly switched off then turned back on on a couple of those hiccups there was a back fire probably thru the intake. i did not see any evidence of running rich like the clouds of black smoke. I had no time to take a look at the plug or see if the oil level rose but i will first chance i get. think its worth looking at the valve adjustment?


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## jhngardner367 (Apr 5, 2011)

Yes,and you might check the muffler,to see if it is flooded with oil,as well.
If this happens,it will run rough(or not at all),and will act like a siphon,and keep flooding.
Try running it with the muffler off,for a bit.It will be loud,but won't hurt it, for a run of 10-20 minutes.


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## ajamieb (Jun 15, 2014)

Thanks for all your help. Its running smooth as silk with full power. Turned out to be an incorrect throttle cable to the governor linkage (for the running badly, hiccup, and backfiring symptoms), maybe the flooding too, not sure since i cleaned the needle valve one bad test drive before i corrected the governor. Now that everything is good the nightmare turned into an excellent learning experience.


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