SHED diaphragm or fuel bowl vent valve

[ryan427]

Does anybody have a tutorial with pics for sealing this shut? I am pretty sure (from the looks of it) that the diaphragm in mine is shot and causing a vac leak. I've read instructions on sealing it shut but I can't seem to grasp it. Pretty sure this has to do with some sort of learning disability I think I have. Makes it hard to visualize a concept at times. Anyway, I'm trying process of elimination before replacing the carb. I've read about the problems it can cause... Seems to be exactly what I am dealing with. Here is the link where I read about it:
89 Accord hesitation and shaking - Drive Accord Honda Forums

Really hoping I'm not sounding like a complete idiot here. Ryan

[g.frost]

I've never heard of such a thing on these carbs, nor can I find it on the vacuum diagram. I'll believe when someone posts a picture of what and where it is. As far as I am aware, the fuel bowl is vented through a (diagonal) tube that ends above the carb in the air cleaner box. There is no valve or diaphragm that I am aware of. ....but always ready to learn something new here. Thanks.

[ryan427]

I hadn't either until I started digging around. This is a picture of it with the cover off. Someone else took this picture as I found it on the web :-) The cover has a connection for vac hose...

I've never heard of such a thing on these carbs, nor can I find it on the vacuum diagram. I'll believe when someone posts a picture of what and where it is. As far as I am aware, the fuel bowl is vented through a (diagonal) tube that ends above the carb in the air cleaner box. There is no valve or diaphragm that I am aware of. ....but always ready to learn something new here. Thanks.

[airporter]

I hadn't either until I started digging around. This is a picture of it with the cover off. Someone else took this picture as I found it on the web :-) The cover has a connection for vac hose...

Ryan, that is the picture of the air vent cut-off diaphragm. The test for it is on pg. 11-80 in the Service Manual. You can look around and find a manual to download.
OR, as AC Mechanic said in your original post, You can suck on the hose attached to the diaphragm and see if it holds vacuum. I could not find a new shed diaphragm kit. If the diaphragm is bad you can seal up the cover and plug the vacuum hose ( NO. 8 ).. g.frost... The Evaporative Emission Controls diagram on pg. 11-76 shows the Air vent diaphragm.

[ryan427]

Gotcha. That's where I'm stuck. By "sealing up the cover", do you mean filling it with silicone and/or JB Weld? Do you also glue shut the plunger? I'm probably overthinking it. Ryan


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[airporter]

First I would make sure the diaphragm is bad. You need to get a hand vacuum pump. They are around $50. There are a lot of tests on your Honda that require a vacuum pump.
Or you could do like AC Mechanic did ( Its in your first post ......post #7 ) he sucked on the # 8 hose that is connected to the air vent diaphragm and determined that it was bad. He then forced the valve open & plugged line # 8. I have never had to do this.... my diaphragm tested good.
You may be able to remove the plunger I don't know. You can plug the hose with a plastic plug they use to plug drip hoses or if the hose is connected to a metal line you could cap it off. You need to either force the plunger open or remove it.
And you could seal the hole in the cover with JB Weld.

Do you have Smog check requirement?

Also this guy found a used diaphragm : Mr. Hankey Archives

[ryan427]

Good points. I did a vac test and it failed. No smog checks here so we're good. I still can't wrap my head around this. The reason is, if you take the cover off, there is a spring. So, when the engine is running, the plunger is pulled toward that cover you have pull off to access that very plunger (via vacuum). When the engine isn't running, the spring pushes the plunger closed. I understand pulling the vac line and capping off both ends. I can pull the plunger out (it only pulls out about 1/8inch toward the driver side fender.

But how would I keep the plunger from closing again? I can remove the spring but I would think vibration from the motor would eventually cause it to close again. Or does it matter since both the vacuum ports are capped off? I am sorry I can't seem to grasp this. If you're frustrated and don't want to reply, I'll understand. Thanks.




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[airporter]

No frustration here hell its raining and I have some time!
OK so you have a bad diaphragm basically a leak into #8 hose.
I have never done one of these ..... I was hoping one of the senior members would give some advice.

First.... plug the vacuum hose # 8 thats connected to the cut off diaphragm If the engine runs better then I would continue.

Referring to the Diagram on Page 11-76 if the plunger is open or closed the carb bowl is still vented. The air vent shutoff valve just diverts the fumes to the charcoal canister when the engine is off.So the engine should still run ok.

If the engine still runs rough you should consider getting the carb rebuilt. just my humble opinion

I had my carb rebuilt a year ago it was hard to start it runs great now.

PS I'm really having a hard time posting here. I submit a post and get message that I'm not signed in. Then , when I sign in again, some of my text is missing. ??

[ryan427]

Cool. I will give it a shot. I'm considering ordering a rebuilt carb from the import carb guy online. 180 bucks. After I make sure everything else is working, that'll be my last resort. Thanks for the advice!


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[ryan427]

Happy to report that this procedure improved the performance. I lodged a vacuum port cap in the plunger to keep it open at all times. DC'd the vacuum hose and capped off both ports. Smoother idle, better acceleration etc. The hole in my diaphragm was pretty small. My neighbor had a big one in his so the difference was more noticeable. But I'm happy with how this turned out.


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