Briggs and Stratton carb # 798758 problems

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  #1  
Old 03-13-16, 02:43 PM
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Briggs and Stratton carb # 798758 problems

I believe the gas had some dirt and water in it when my son used it last. It will only start when you pour gas in the carb. then quickly dies. I removed the carb and cleaned screens. Cleaned the areas where the screen sat. I removed the pick up. I can blow through it but only when its not attached to the carb. The primer bulb when pressed stays pressed in so I assume there's a clog somewhere? Diaphrams appear intact and flexable. I tried an air compressor on the holes. Any suggestions other than a new carb?
 
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  #2  
Old 03-13-16, 02:51 PM
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If you can take some of the gas out of the tank & put it in a clear container, you'll be able to see right away if there is water in the gas. It will separate like oil & vinegar salad dressing.
 
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Old 03-13-16, 02:59 PM
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the first thing i did was replace the gas with fresh gas
 
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Old 03-13-16, 04:07 PM
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What piece of equipment is this on?
Is there a fuel pump, filter in the tank?
Just blowing air into it's not going to do anything.
Need to pull it off and use carb. cleaner.
Better yet buy a rebuild kit since you'll have it all apart anyway.
Been using ethanol fuel, sure way to have carb. and fuel line issues.
 
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Old 03-13-16, 07:44 PM
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its a bolens lawn mower. a rebuild kit is essentially the whole carb, otherwise you just replace the diaphrams which seem to be in good shape. The pick up tube has a screen, but you cant blow air thru it unless it's detached. I think thats the clog since thats the fuel feed. any way to clear that?
 
  #6  
Old 03-14-16, 12:40 AM
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If the primer stays depressed, the check valve behind it is likely stuck. Will the primer release with the carb off the tank?
 
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Old 03-14-16, 04:08 AM
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I've seen videos to replace the primer bulb , so I may just pull that off and see what I can find
Yes, it does release when the pick up is not in the tank of gas
 
  #8  
Old 03-14-16, 11:37 AM
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Those plastic carbs are so easy to work on.

get you a diaphram and gasket for 3 bux spray carb cleaner in the carb and in the tank.

Rinse tank out with a little gas. Put it back together and you should be good to go.

You have a bad diaphram most likely.
 
  #9  
Old 03-14-16, 12:23 PM
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My standard post:
You need to install a new diaphram kit, it is Briggs part # 795083 or old # 495770 also Lowe's has a kit #5083 which has the same parts.
Here we go:

Remove air cleaner, there are 2 bolts that hold things together, one on the front of the tank 3/8" and one into the block 1/2", remove these bolts, now "slowly" slide the carb/tank off the intake tube and breather tube, now tilt the tank in to release the throttle linkage and waalaa the carb/tank is removed. Check the intake tube to see if the O ring seal and plastic retainer are still on the intake tube, if so remove them and re-install them into the carb. Remove the 5 screws from the carb/tank remove carb(don't loose the spring) now spray all holes, cracks and crevases in both the carb and tank surface with brake parts cleaner, remove the main screen(looks like a thimble), now with a small screwdriver pry out the main jet(carefully) and clean it, check the O ring on the main jet for damage, if it is damaged it must be replaced, reinstall the jet, it can be difficult some times to get it to snap back in place(I use the rounded end of a screwdriver handle). Remove and clean the fuel pickup stem(not necessary if the fuel tank was clean). Clean any junk/rust from the tank. Install the diaphram on the tank then the gasket(no goo or sealer) now carefully replace the carb(the spring will try to misalign the diaphram), tighten all screws a little at a time so as not to crimp the diaphram until they are all tight. Install the carb/tank in reverse order and you are done. If I missed something one of the real mechanics will correct me. Have a good one. Geo
 
  #10  
Old 03-14-16, 02:26 PM
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Hummm , the diaphram appeared ok when inspected. The Bulb will not release when pressed. The pickup tube is clear, but when installed I cannot blow through it so I assume its something between the pickup and the primer. I haven't removed the primer bulb yet. Is there something in there that I can possibly clear? I don't see the point of installing a new diaphram kit if something else is the problem.
 
  #11  
Old 03-14-16, 05:52 PM
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The diaphragm is normally the problem and it should normally be replaced once you remove the carb. That's why so much emphasis is placed on it.
 
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