Pulsa-Prime Carburetor Won't Prime

[Merkava_4]

Briggs & Stratton Engine 10M902 0487 E2 05101754
Briggs & Stratton Carburetor Model 795475
Craftsman Push Mower Model 917388920
Serial Number 1129 05M 023952

This is that little tank mounted plastic carburetor. Primer bulb does not suck up fuel when I push it. The bulb is not torn and the carburetor is still pretty much new. I bought it last November 30, 2014. However, I have taken it off a few times to clean out the screens whenever the engine has had a surging issue. After cleaning the carburetor each time, the engine runs fine again. I'm in uncharted waters this time. I've never had the primer bulb not prime. Please help.

[KE4AVB]

It been a while since I have had priming problem on one these.

If I remember correctly the check valve (item 913) can be struck or not sealing. It is located inside the primer chamber. In order to get to it the primer bulb must be removed. Also the fuel pump diaphragm (item 394) can cause this problem especially if installed incorrectly.

[bgsengine]

It been a while since I have had priming problem on one these.

If I remember correctly the check valve (item 913) can be struck or not sealing. It is located inside the primer chamber. In order to get to it the primer bulb must be removed. Also the fuel pump diaphragm (item 394) can cause this problem especially if installed incorrectly.

Yup and repeated removal and reinstallation of those carburetors, especially if not paying attention to torque of the screws, can result in warped carburetor body causing same issue. should not have to clean that frequently - if you are then you need to change your fuel storage habits and/or refueling habits.

[Merkava_4]

Alright fellas, this is what I did today:

1. Went to yardage store and bought a #5 crochet hook.

2. Went home and pulled carburetor for a complete disassembly
including the primer bulb, rubber seat, check ball and spring.
I even removed the throttle valve and emulsion tube.

3. Performed a thorough cleaning using a jar of carb cleaner
and an acid brush.

4. Reassembled carburetor and mounted it to the tank using
the correct torque sequence as shown in the manual.

5. Reinstalled blower housing and air cleaner assembly.

6. Filled tank with fresh clean fuel.

7. Pushed primer bulb and after about 10 pushes, it
finally filled up with fuel and primed the carb.

8. Pulled rope and engine fired up on the first pull.

9. Took the mower out for a spin and cut some grass.
Engine running just fine.

10. Shut off engine and let it cool for two hours.

11. Went back to mower and pushed the primer bulb
several times. Primer bulb not drawing fuel. I'm back
to square one.

[bgsengine]

Alright fellas, this is what I did today:

1. Went to yardage store and bought a #5 crochet hook.

2. Went home and pulled carburetor for a complete disassembly
including the primer bulb, rubber seat, check ball and spring.
I even removed the throttle valve and emulsion tube.

3. Performed a thorough cleaning using a jar of carb cleaner
and an acid brush.

4. Reassembled carburetor and mounted it to the tank using
the correct torque sequence as shown in the manual.

5. Reinstalled blower housing and air cleaner assembly.

6. Filled tank with fresh clean fuel.

7. Pushed primer bulb and after about 10 pushes, it
finally filled up with fuel and primed the carb.

8. Pulled rope and engine fired up on the first pull.

9. Took the mower out for a spin and cut some grass.
Engine running just fine.

10. Shut off engine and let it cool for two hours.

11. Went back to mower and pushed the primer bulb
several times. Primer bulb not drawing fuel. I'm back
to square one.

carb or tank is warped - Get a second diaphragm kit for it and double up the gaskets using the new gasket and an old "good shape" gasket abnd see how she works then.

[Luffydog]

sounds like it alot time to buy a new carb after doing all that you almost or could have a new one..

[Merkava_4]

It was the diaphragm.

I disassembled the carburetor again last night but this time I tried priming the carb before mounting the tank back to the engine. While I was tipping the tank side to side, I noticed fuel running out from the carburetor/tank mating surface. Removed the carb from the tank and saw part of the diaphragm stuffed down in one of the holes for the mounting screws. The diaphragm had gotten wavy around the edge by being off the tank so many times. The service manual says the diaphragm is fine as long as it's not torn and as long as the flapper valves are laying flat. Well, lessoned learned here is that the diaphragm can't take too many removal and re-installations. Now I know why they sell them on ebay in packs of 10.

And another thing I learned from all this: The diaphragm and gasket must make an air tight seal between the carburetor and fuel tank in order for the primer to work! bgsengine should've told me all this ahead of time.

[Arkie]

I just can't seem to force myself and have any faith in my work re-installing a used carb diaphragm that has the small flapper valves, even if it looks ok. Seen failure too many times.

Just asking for intermittent troubles that I asked for by doing so.