Carter WDO carb that is leaking from just one side/venturi

[m-mman]

 

This is a Carter WDO (1942 Hudson)  that I just rebuilt with a kit from the Carb King.

 

Everything works well EXCEPT that it is leaking fuel from one side/venturi.  

 

The metering rods move freely. I swapped the jets just in case there was a mismatch between the metering rods and the jets. Still leaking on the same side. 

 

I would think that the fuel would only be drawn out of the venturi if there is adequate vacuum etc, to do so. If both sides were dripping it should indicate an environment that is affecting both sides. 

 

What might be causing a drip from just ONE side? 

 

 

Another view

 

 

[Bloo]

Do both barrels feed into a common area? Is this a six or an eight?

 

Assuming both barrels feed into a common area, the most likely thing is one barrel is passing more air than the other. I would hold the throttle body up to a light, close the throttle, and see if one throttle plate has a bigger gap around it than the other, or if a plate could be loose.

 

[carbking]

The one side is pulling fuel through the main circuit rather than the idle circuit.

 

Do a compression test on the engine. 

 

If all cylinders are good, remove the carb, and check the throttle body where the idle mixture screws exit to see if there is a crack in the throttle body.

 

If no crack, again disassemble the carb, and interchange the idle tubes to see if the drip follows the idle tube.

 

And while you are inspecting the throttle plates as Bloo suggested, check to make sure some previous rebuilder has not installed one of the plates upside down (look at the taper on the edges).

 

Jon.

[m-mman]

1. It is an 8

2. Compression is 90-105. It runs smoothly 

3. Well, now I have something to check out tonight.  

Thanks, and I'll report back. 

[m-mman]

Report on today's work:

Pulled the throttle body - no cracks

Swapped the idle tubes - no change still leaked on the same side.

Examined the closing of the throttle plates (they were installed correctly) I could see light around the edges, but how much is too much? (are there specifications for this?) I loosened the screws (surprised that they seem to be adjustable) closed the shaft, and was able to decrease the amount of light I could see (at least I think it was less) 

 

Reinstall and insure that the throttle is as closed as possible (back the screw out and hold the linkage closed).

I could now get the leak to stop occasionally. I was opening, closing and hold closed the linkage. So I believe that the throttle plate is/was  not sealing 100% (I have never seen this before) 

 

Open up the parts carb and its throttle body has even less light shining through. So I swapped the throttle plates and now I can (reliably) get the throttle closed enough to stop the leak (on the problem side) This is at a low idle of maybe 500 or less RPM. Crack the throttle even a little and the leaky side flows sooner and fuller than the other side. (I am talking milliseconds) 

 

So it is working now such that I CAN get it to stop leaking at idle <hooray!> (but it must be a very low idle)

I am satisfied, the car is drivable, and I can go on to sorting out all the other issues. But is interesting how sensitive one side is over the other. 

 

I might clean up the parts carb throttle body swap the good throttle plates back in it just to see what happens.

But that will have wait for another free day.   Thanks for all your suggestions. 

[Bloo]

I think you still have something wrong if one side behaves differently than the other. The throttles don't normally run COMPLETELY shut, just almost shut. The idea of looking at the throttle was to see if one side might have a lot more gap than the other. I have seen carbs, newer ones, where the throttle shaft and bore wore out and allowed the plate to drag on the bore. Metal wore off of the throttle plate, leaving a larger air gap on the barrel that had the linkage and the return spring.

 

The two sides should behave the same. You might check for vacuum leaks. Do both barrels feed completely separate runners like they would on an older V8? I would expect both barrels to dump into the same plenum on an inline engine like yours, but if they are completely separated, that opens up more possibilities for the cause.

 

Anyway, I'm glad you are making progress with it.

 

Edited December 11, 2021 by Bloo (see edit history)