PMO gas leak

[zenithblue71T]

Hi guys, have any of you seen this type of PMO gas leak on my right side? See pic. It’s a dribble at best. I did get a heck of a backfire once. Any idea how I can fix this?

[1QuickS]

Possibly it is that fuel in the galleries feeding the accelerator squirters percolates thereby discharging fuel onto the closed throttle valves, this fuel then migrates along throttle shafts which then exits on the middle throttle bore. The ends of the PMO throttle shaft have seals which preclude gas exiting there.

Why the right side only? Maybe the oil cooler and oil tank being on that side contribute more heat than on the left side.

Try installing insulators or perhaps two sets.

See my posting about this here:

https://www.early911sregistry.org/fo...ht=percolation

[Scott A]

Mr Paul Abbott,
To be simple, I think you are a national treasure.

I’ve always been into carburetors, maybe because I needed them to get me places.
I really enjoy your write-ups on this site and online.
I find it immensely helpful. I feel very fortunate to read from someone that spends so much time with these mixers, and someone who is so willing to share even the tiniest detail.

I often thought of trying to learn the trade from you and continue your knowledge.
But I moved away from Oregon to the East.

Thank you. Scott

[1QuickS]

Wow! Thank you Scott!

"One is glad to be of service." Robin Williams, Bicentennial Man

[zenithblue71T]

I spoke with PMO factory tech and they said to snug the nuts at the accelerator pump. This seems to have worked. I also used brake cleaner to clean the grimy areas, which I know is not approved, but I quickly did it anyway. I also reset the Jets Airs and Etubes to factory spec going with 125 jets 170 airs and F 11 emulsion tubes. Unfortunately, the stumble I corrected at 3500 RPM is back in a more pronounced way. But at least the car shouldn’t be lean anymore.

[Nickelplated5s]

Mr Paul Abbott,
But I moved away from Oregon to the East.

Thank you. Scott

Pretty sure he is in the upper NE now. There is always shipping...

[zenithblue71T]

Hey Paul, my cylinders are now filling with gas. Could the leak you mentioned be flooding my spark plugs and preventing start up? I used to leave the throttle level next to emergency brake up a bit. I now make sure it’s all the way down when I shut off the car. Perhaps that’s flooding the engine? Carbs are only 5 years and 10k miles old.

[1QuickS]

If an air correction jet for the idle/progression circuit is blocked by debris then this would create a siphon that would drain your float bowl into your cylinder. This can happen since the air corrector is located at the top of the throttle body and when the suction created by intake manifold vacuum is stopped, fuel in the gallery feeding the progression circuit would normally drain out into the engine. This is the fuel from the idle jet down to the progression drillings and mixture screw. Fuel in this circuit on the float bowl side of the idle jet would return to the float bowl. The idle air correction jet provides a break of the siphon that would occur if this air correction jet was blocked with debris.

A blocked idle air correction jet is not uncommon with PMO carbs. Richard Parr has recommended to EMPI (buyer of the PMO product line) to revise the top cover of the carbs to make it more difficult for debris to block the air corrector jets. (He has found EMPI to turn a deaf ear to his inputs.) I have provided information regarding "Sources of Debris in Webers" on my website; mostly due to imperfect sealing of the air cleaner housings with the air cleaners. I applied self-adhering, foam strip to the edges of my air cleaners to provide positive sealing with my air cleaners housings. These interfaces are not precision surfaces and the chance of debris being sucked into the carbs through discontinuities in the sealing surfaces may allow crud to enter the air cleaner chamber.

Fuel forced out of the accelerator squirter nozzles after shutdown by heat soaking would not have sufficient volume to hydro-lock a cylinder. The gasket in the accelerator pump body positively seals fuel delivery from the float bowls after an acceleration demand (pedal depression) has been completed.

My hot restart posting addresses issues with fuel being forced out of the accelerator squirt nozzles and using your throttle lever to open your throttles after shutdown is a good start but I recommend going a step further as discussed previously.

https://www.early911sregistry.org/fo...ht=percolation

Now, after all this writing, I fully expect to have someone with more sage experience to provide a one sentence response which rectifies your issue. I look forward to this as I may advance my knowledge.

[72targa]

I sure hope EMPI gets it together to provide a fix. All this talk about leaking fuel (and related potential for fire) is starting to concern me.

[edmayo]

After you turn off the engine look down the barrels and see where the gas is dripping from.