2F Engine: Testing the HAC Valve (1 Viewer)

[cbmontgo]

Is there a way to test the HAC valve when off the engine? My manual says that you can blow "into any one of the three ports on top when the engine is idling. If the passage is open, the valve is in the high altitude position. If it is closed, the valve is in the low altitude position".

Would the same prove true if the engine is not idling? Since the bottom tube is only for atmospheric pressure and any of the others can be removed to test the valve, I just wonder if there is a way to test it off the engine.

I think mine has failed, and the passage is closed. It should be open for the high altitude position and lean out the mixture over 4,000' elevation.

 

[2mbb]

you would need to apply vacuum to the middle port near what's indicated as "port B" (the middle port).

 

[cbmontgo]

you would need to apply vacuum to the middle port near what's indicated as "port B" (the middle port).

Thanks! I applied vacuum and still no air passes through the other ports for the high altitude setting. Sounds like I'll be calling CDan on Monday.

 

[cbmontgo]

Well, the old stock is run dry and these are no longer available. Damn.

Anyone know if it is possible to rebuild or repair one?

 

[2mbb]

sor has used ones for sale, or maybe try cruiserparts.net or the for sale section.

There is a metal diaphragm that expands when at high altitude. If the diaphragm has a hole or has leaked it's "pressure" then it won't expand at altitude. You would have to fix the leak and fill the diaphragm to the correct pressure.

If you are spending all your time at high altitude you should be able to bypass the HAC by disconnecting the HAC tube from the distributor advance, plugging the tube and manually advancing the timing. Disconnect the three vacuum lines from the top of the HAC and put filters on them to allow them to lean out the carburetor.

 

[cbmontgo]

sor has used ones for sale, or maybe try cruiserparts.net or the for sale section.

There is a metal diaphragm that expands when at high altitude. If the diaphragm has a hole or has leaked it's "pressure" then it won't expand at altitude. You would have to fix the leak and fill the diaphragm to the correct pressure.

If you are spending all your time at high altitude you should be able to bypass the HAC by disconnecting the HAC tube from the distributor advance, plugging the tube and manually advancing the timing. Disconnect the three vacuum lines from the top of the HAC and put filters on them to allow them to lean out the carburetor.

SOR has them, but they are pricey and have no returns accepted. I bought my current one used, and it obviously got me nowhere. I just really hope that I can find one on 'Mud that works. Otherwise, I may need to bypass it like you said. Thanks for the help.

 

[FJ40Jim]

I have several HAC valves for sale cheap, from late model FJ60's.

Post up if you're still looking for one and I will test one to see if it is working at low altitude.

 

[cbmontgo]

I have several HAC valves for sale cheap, from late model FJ60's.

Post up if you're still looking for one and I will test one to see if it is working at low altitude.

I am still looking; one person has PMed me and he is trying to test it to make sure it works. I am needing to buy one that definitely works, so please let me know if you are able to confirm that one of yours does.

Thanks for your help, Jim.