Gas leaking from primer bulb

[jimhokie]

Craftsman mower model 917.377530, Briggs and Stratton engine model 12H802-2675-E1: I pulled this mower out of my garage for the first time in about 5 years to clean it up to sell. It worked last fine time I used it...I just replaced it with a new mower with a larger bag capacity. I added about a quarter tank of gas just to see if it would fire up, and went to get some Seafoam to add to the gas assuming the carb would be likely gummed up. When I got back to the mower, I noticed gas was dripping out of the primer bulb, apparently from a hole in the tip. I figured the bulb had dry-rotted and formed a hole. But wanting to just see if it would start, I pushed the primer bulb 3 times, covering the hole in the tip, and it started on the first pull! I let it run for only a few seconds since I'm sure it needs fresh oil.

Assuming I needed a new primer bulb, I took the cover off the carb and pulled the primer bulb out. But it appears that the hole in the bulb is by design, which I later read could be the case for a primer bulb. So my questions are, is there really supposed to be a hole in the bulb for this engine, and if the hole is supposed to be there, why does gas leak out of it? Is there a bad seal somewhere else that is providing a vent to allow it to leak from the primer bulb hole? Any ideas for what may be the problem?

Thanks for any thoughts!

Jim

 

[Rivets]

Yes, the hole is supposed to be in the primer bulb. I suspect that the float needle is not seating properly and you will need to replace the float needle and seat. Part number 398188. This is a procedure to do so.

Needle and seat replacement

Remove the carb, and then remove the float bowl. Check the float bowl jet (which is the bowl screw) and make sure the jets both horizontal and vertical are clean and open. Tip the carb upside down and remove the float pin and float with needle attached. Look in the float needle passage and you should see the red float seat at the bottom of the passage. This is where a #5 crotchet hook would come in handy as you need to remove this seat. If you have no hook, but compressed air, you can blow through the fuel inlet and try to pop the seat out. Put your thumb over the passage to prevent the seat from flying who knows where. No air or hook try bending a stiff paper clip to dig the seat out.

With the seat out clean the passage way with carb cleaner. Now you must find a drill bit slightly smaller than the passage way, to be used to press in the new seat. Apply a very, very small amount of a very light lube to the new seat. 3-1 oil or lighter, to help seat it better. Carefully insert the new seat in the passage way with the rings on the seat down toward the carb body. Slowly and carefully force the seat down with the back end of the drill bit. Once it is seated, check to see that it did not flip and the rings are up. If everything looks correct, attach the new needle to the float and install with the float pin centered. It everything is correct, the float should seat level to the carb body, when looking at it upside down. If everything looks good reattach the float bowl, making sure that both the bowl gasket and the nut gasket seal properly. Reinstall on the engine and test unit. Remember to have patience and take your time. Good luck, but I don't think you'll need it.

PS: *On the side of some Tecumseh carbs you will find a plastic cover. *Under this cover will be an idle jet. *Remove it and check to see that theist is open both horizontally and vertically. *You should be able to push the old float needle wire through the vertical opening.

 

[jimhokie]

Thanks for the great info and instructions, Rivets! I took the carb apart, and it was very gummed up. The float would not pivot easily...it would pretty much stay in whatever position I put it, so the needle wasn't closing against the seat for sure. I have a whole new carb overhaul kit on order that includes the float needle seat. Meanwhile, I cleaned everything with carb cleaner, including the pin that the float pivots on, and the holes in the float and carb that this pin go through...now it pivots freely. I pretty much destroyed the seat trying to get it out. I had to thread a wood screw into it to get enough traction to pull it out...it was really glued in there. Hopefully, the new seat goes in OK.

One question though, on your comment "Check the float bowl jet (which is the bowl screw) and make sure the jets both horizontal and vertical are clean and open." I could pass a paper clip completely through the horizontal hole. I assumed the vertical hole meets the horizontal hole like a "T", but the paper clip doesn't go all the way down to the horizontal hole. Does the vertical hole somehow curve toward both horizontal holes? It appears that carb cleaner blew out of both side holes when sprayed into the top center hole, so I think it's clear.

I should have the carb overhaul kit by Thursday, so hopefully that will do the trick.

Thanks again!

 

[Rivets]

You are correct about the main and as long as carb cleaner came out both sides, you're good to go. One thing, look on the bowl screw again, some had a very small jet at the top of the threads. This manual might help also.

http://dl.dropbox.com/u/12502267/B&S Service Manuals/01_270962SingleCylinderLHead.pdf

 

[jimhokie]

Well, I finally received the carb overhaul kit (after having to reorder when the first kit arrived with the boxes crushed and several small parts were missing, including the float needle seat). I installed it and everything seemed to go together correctly, but when I added gas to the tank, it started leaking through the primer bulb again, just as before. I used the flat end of a drill bit that just fit inside the hole to press the float needle seat into place. I sprayed a lot of carb cleaner through the hole before installing the seat. Is it possible to over-compress it into place? Or what else could I have done wrong?

 

[Rivets]

There are two things to check. First, did the bowl gasket twist or fall in when you tightened the bowl screw? If the gasket does not seal properly, it will cause the float to not seat properly. Second, did you check the float level? If you tip the carb upside down it should be level or tipped up a little. (Meaning the side away from the needle is slightly higher than the needle side). When I finish setting the float level, before I install the float bowl with the carb upside down, I blow as hard as I can (with my mouth) through the fuel inlet. I know it tastes bad. It should take a pretty strong blow to open the valve. Reassemble and attach the fuel line to check before you install on the engine. You should not see fuel coming out anywhere. Let me know what happens.

 

[jimhokie]

Rivets, before seeing your last response, I took the carb apart again to check the float action. I confirmed that the float was almost level while holding the carb upside down. It did stick on the edge of the post that the bowl screw threads into, but I don't think that would be possible with the bowl attached. I was careful about ensuring the bowl gasket was seated properly while attaching the bowl. After reinstalling the carb on the engine, I left the air filter housing off so I could see any leakage right away. When I added gas to the tank, it did start leaking again. I then tapped the bowl with the end of a socket wrench a couple times, and the leakage stopped! So apparently the float was not freely floating as gas filled the bowl, but a little "percussive maintenance" freed it, allowing the needle to seal. (Maybe the needle point was not aligned in the seat hole initially...maybe it was stuck on the edge until I tapped it?) It started up fine several times, but I needed to press the primer bulb each time to start it. Usually, once it was warm, it would start without having to prime it. But the leakage problem has apparently been fixed.

But now that it is running, I remember another reason why I stopped using this mower and bought another...it runs too slow! There is no manual throttle control to adjust the speed. It is painfully slow to walk behind at the speed the self-propelled wheels turn. I can manually nudge the throttle control on the carb to speed it up, and I remember trying to wedge something against it to hold it at a higher speed back when I was still using it, but could never get that fix to last for long. Is there any speed adjustment in the carb? I don't remember seeing any kind of adjustment screw, but wasn't really looking for that either. Or is there an adjustment to be made in the throttle cable? This mower has one of those bars you have to pull up against the handle to start it and keep it running. Maybe this bar no longer pulls the cable far enough? Any ideas for me here?

 

[Rivets]

On the governor link which runs from the air vane to the throttle shaft, you should have a governor control spring. On the end of the spring, not attached to the link, should should be able to bend the metal tab it is attached to. By bending this tab you will be adding more tension to the spring and increasing the RPM's. I would also go back and make that float move very freely, so you will have no problems in the future.