B&S 10A902 Engine Primer Mechanism Not Working - Primer Bulb is OK

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  #1  
Old 03-20-11, 06:38 AM
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B&S 10A902 Engine Primer Mechanism Not Working - Primer Bulb is OK

Hello,

I have a lawnmower with a B&S Engine. The engine numbers are:

Model: 10A902
Type: 2171-E1
Code: 98111025

The engine was originally running rough (surging and sputtering) and the primer was working fine. I removed the carb, cleaned it all up, replaced the diaphragm/gasket and it will now not prime. I used strating fluid and it started right up and ran great. Once it's warm, it will start every time and run great. I let it cool and filled the tank to about 3/4 to be sure that there was enough gas and no matter how many times I prime, no gas squirts out anymore. I removed and isnpected the primer bulb and it seemed fine. I replaced it anyway and the problem still exists. I removed the check valve in the priming cavity between the primer and the carb air intake and cleaned the cavity, spring, ball, etc. and still no priming.

One thing I just noticed is that the B&S web site calls out for Diaphragm Kit 495770 for Date Codes prior to 07080800 and I was given Diaphragm Kit 795083 which is used for Date Codes after 07080800. Is there a chance that this incorrect Diaphragm could be the source of my primimg issue or are there other things that could be looked into. This seems like such a simple mechanism and I would like to avoid the purchase of a new carb even though it's only about $30.

Thx,


Joe
 
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  #2  
Old 03-20-11, 11:57 AM
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Hello Joe,

The diaphragm is just fine, The 495770 number superseded to the 795083 number which is a direct replacement part.

Now, You said you removed the primer spring and ball along with the ball seat for cleaning. This ball seat must be installed with the ring impression facing out toward you and the smooth side facing inward to the ball, If you happened to install it backwards the ball would likely not seat and cause a non working primer system.

Also make sure you push the primer bulb in all the way when installing so both tabs on each side of the bulb retainer lock into their respective slots.
 
  #3  
Old 03-21-11, 07:55 AM
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Hello 31YTech,

Thank you for the feedback.

I removed the ball seat, ball and spring only after the priming mechanism was not working. I did install the seat properly as I noted the orientation when I removed it. I also was sure to install the bulb properly and the tabs seated in the slots as intended.

Is there anything else that I should be looking at? It seems to me that there is an air leak somewhere.

Thx,


Joe
 
  #4  
Old 03-29-11, 06:44 AM
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Update: I ended up troubleshooting the priming mechanism by using the bulb and blocking the hole where the gas shoots out while the bulb was sucking back air. This simulated the functionality of the ball valve between the priming bulb and carb as it should not suck back air but gas from the tank. It worked fine and gas shot out as I pushed in the priming bulb again. If i repeated this, it sucked gas from the tank as I released the bulb (and put my finger over the hole where gas should shoot out) and shot gas into the carb as I depressed the bulb again. This meant that either the ball seat is defective or the carb body where the seat, valve and spring reside is deformed. I purchased a new seat, ball and spring, installed and all works fine now. While the ball seat looked fine upon inspection, it must have had a leak somewhere not visible to the naked eye.

Thx,


Joe
 
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