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Honda EM3500 SX auto choke not closing

2591 Views 2 Replies 2 Participants Last post by  Dave Hill
Hi Folks:
I have the above generator and this problem is driving me nuts!

I can start it using manual choke, once engine starts running the vacuum choke servo or diaphragm will pull the choke open. When I shut engine off, the choke remains open and the vacuum diaphragm continues to pull on the choke leaving it open.

If I disconnect the vacuum line to the diaphragm, it releases and the choke returns to closed position. Unless I disconnect the line, the vacuum stays applied to the diaphragm even when engine is off.

There is a check valve and an electric switch solenoid in line with the vacuum hose. Both appear to be working okay. If I apply 12 volts to solenoid it 'clicks' and closes, not allowing any flow. Disconnecting power to solenoid it 'clicks' and allows air to pass through it. The check valve also seems to be okay. I can blow through it one way but not the other.

For the choke to come on, there seems to be a need for the applied vacuum to the choke diaphragm to be released or dissipated before the diaphragm will move and allow the choke to return to closed position. This is not happening, in other words the vacuum applied to diaphragm is held constant or never removed preventing the choke from returning to closed position.

Even when this system is functioning properly, I cannot see how the vacuum that's applied to the choke diaphragm can ever be released when the check valve prevents it.

Something has to release the vacuum applied to the choke diaphragm when engine is stopped. What is it? I gotta be missing something here?

Any suggestions would be appreciated.

Thanks very much.

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Dave I'm thinking out loud here, because I work on these from time-to-time, but I've never had to chase a choke issue, nor have I really studied it's operation....because they always seem to work.

That said, are you sure you have a problem? As long as you can manually close the choke door using that metal hoop that you pull out, the generator will start, and then my experience has been; push the metal rod back in, and the engine will let go of the choke door as it warms up, thus opening the choke door fully after a few minutes of run time. It sounds like that's what yours does.

So when it's time for a restart, you just manually close the choke again, give one pull, and the engine is running again.
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To conclude the this thread, I believe this problem has been resolved.

I replaced the check valve which Honda calls a 'dashpot'. The part cost $28. Once installed the choke works like it should. Thanks to Robert from Honda in explaining how the autochoke operates on this model. It got me thinking the only possible culprit could be the check valve.
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