I was working the throttle back and forth on my Motorcraft 2150 (with the engine off) when I noticed a little bit of fuel had settled right around the throttle shaft spring. I wiped it off, and nothing else came out of it. I went back a few days later, and it was still dry. I drove the truck, and it is still dry. But when I had to work the throttle again to make another adjustment with the engine off, the same thing happened. Just a little bit of fuel seeped out from the throttle shaft. Is this normal?

 

Could have a little wear around the throttle shaft, and working the throttle will actuate the accel pump squirting a little fuel in. If there is a little wear around the shaft, fuel could seep out under this condition.
It bears stating, the motorcraft carbs are not prone to wearing around the throttle shaft, but it can happen.

 

The accelerator pump discharges fuel above the throttle shaft and the fuel sits on top of the butterfly valves. Any wear in the throttle shaft and a bit of fuel can leak out.

 

Make sure a seal didn't break (from being old)

 

If you want to be sure, park it on a side hill, passenger lower than drivers side and do the same thing, if it doesn't seep out or comes out the other side then you know that its just running along the thottle shaft. Or open it about a quarter throttle and try to wiggle the throttle shaft. Doesn't need to be very loose to do what you are describing..

 

Actually, this is a pretty common issue as Motorcraft carburetors do not have bushed throttle shafts. Throttle shaft play is something important to look for when picking up a used carburetor at the junkyard. Some rebuild houses will bore and bush the throttle shaft during remanufacture.

The fuel seeping is not ideal, but pretty common. If it's just enough to get the return spring damp on occasion and it's not dripping onto the manifold, you should be fine. If it's a significant fuel leak, I would replace. Use your best judgement.

 

Thanks, fmc400. Pretty normal, eh? Did these carburetors do this when they were brand new? Will this seepage get worse the more it is used?

I'm not sure what my "best judgment" should be because this is my first carbureted vehicle I have ever owned. It's just enough to get the return spring damp, and not a leak that shows up on the intake manifold. But why does it only show up when the engine is off and I am working the throttle arm? Why doesn't is seep out when the engine is actually running?

 

Because with the engine running it is sucking the fuel into the engine.

 

Well now, that makes total sense, doesn't it!