Help.. I can't install diaphragms!!

[peteclark3]

Hey everyone, I am new here. My name is Pete; I got into repairing mowers because my son took an interest in lawn mowers in general when he was 5.. He just turned 8. Everything I have learned I have learned over the past few years.. YouTube, repair guides, forums, etc.. because he has had an interest in learning about engines and repairing them. He's very smart, has a great memory, and definitely knows more about repairing mowers than I do, but he still likes me to do the repairs with and/or for him, so I thoroughly enjoy it. It's also kind of cool that I can usually fix these things up.. I love to troubleshoot in general. I'm a 15 year software programmer by trade.. Right now am focused on mobile app development.

So now, my question! I've tried to replace diaphragms on 2 different mowers now. One older snapper (my son loves the older equipment) .. and just now a poulan .. Both push mowers. Problem is, no matter how clean I try to be, how precise, they always end up leaking after I reassemble. I just tried my second go on the poulan, and it still leaks.. Much worse than the first one I put on.

Can anyone give me some pointers on how to do this right and leak free? Could I be over tightening the screws?

Thank you and looking forward to being a member!!

Pete

 

[Duffer72]

Engine #'s on both would help to see what you are working on or at least some pics

 

[reynoldston]

I take it you are talking about the fuel pump or needle valve diaphragms on a Tillotson 2 cycle carburetor? Yes you can over tighen anything. That I have done with them is frist give then a light coating of light weight clean oil. Make sure all of the old gaskets and old diaphragm is cleaned off the carburetor and when you tighen the screws tighen them even and across from each other.

 

[peteclark3]

Snapper engine (Briggs) -
92908 1826-01 78091108
Mower model - v212

Poulan Pro (briggs) -
10T802 1098 08122354
Mower model - 961240002 00

 

[Duffer72]

I assume you are saying they leak between the tank and carb correct?

You are doing this with the assy off of the engine and the fuel tank flushed and empty? I always found the easiest way was to place the diaphragm onto the inverted carb and get it lined up with one or 2 screws thru the carb body and then put the the tank onto the carb and flip it over to normal position and install the screws. with phillips screws I dought you are over tightening them unless you are using an impact with a screw driver bit.

Are you using anything very strong to clean it that may be eating the diaphragm, I am at a loss somewhat as I have never had a problem like this in over 30 years, I have seen warped tanks that would not seal properly and wouldn't run correctly but not a leak.

 

[peteclark3]

Yep, tank assembly off.. No carb cleaner.. Just as soon as I start it, I see gas pooling up gradually on the tank, and it appears to be seeping out from the diaphragm.

Not using an impact driver.. Hmm. Maybe I have them on in the wrong order.. The "harder" of the two similar pieces of the diaphragm touches the carb side, and the floppy piece touches the tank, right? This is the poulan I am referring to. Unless the "harder" of the two pieces isn't supposed to be on there at all and was just in the package for shipping? Then I'd feel even more stupid than usual.

 

[Duffer72]

Yep correct on the placement, The harder one (gasket) goes against the carb and the floppy one (diaphragm) goes against the tank, are you installing them together in the same place either on the carb or the tank? your not trying to put it together with one piece on the carb and the other piece on the tank are you? when you took the first replacement one off did it looked damged or folded anyplace ? sorry for stupid questions but just really at a loss and am just trying to thinkl of what you may be doing or not doing.

 

[peteclark3]

Nah, didn't look damaged.. Just firm and crispy-like. Guess I'll just try it again.
Last questions..

Is it super duper important that all the holes line up perfectly?

Is there any kind of temporary sealant I can smudge on there to help with the seal?

 

[Duffer72]

If the screws go thru the carb and diap and gasket fairly easily then it should be lined up ok. actually you should be able to see the holes in the tank when you are ready to install the screws, if not then it isn't lined up correctly.

DO NOT use any type of sealer when installing.

Hope fully someone else will chime in with an idea.

As an after thought have you looked closely to make sure there is no cracks in both the carb and tank, it could happen if something has been dropped on it at some time, also when you take it apart
again put a small stright edge across the the mounting surface of the tank and check it.

 

[stampy]

Hi I have had in the past very similar problems. Make sure the filter tips on the pick up tube are REALLY clean. Use carb cleaner and blow out with compressed air. It sounds like as you are repairing older equipment and stale fuel blocking the filters makes a HUGE difference. If its a plastic carb the longer tube will pull off with force. Look through it ( Wear safety glasses) and you should clearly be abre to see through.

The problem with the fuel leaking between the car and tank is usually fixed by doing this. Also shortening the governor springs slightly may help but do the above first.