Sound like a bad needle and seat on my demon?

Great68

Founding Member
May 16, 2002
691
0
16
Victoria BC
Last night my car was running REALLY bad, I was lucky to get it home. It started sounding like it was not running on all the cylinders.

I took a look at it today, and the level of the front float bowl was all the way up at the top.

I adjusted the needle and seat until the float level was 1/2 way up the sight window, and it started running again. I then re-did my idle mixture on all 4 corners using a vacuum guage, got it to 15" of vacuum and it was idling great.

I took the car for a long drive today and for the most part it was driving great, no part throttle bog, no rich exhaust smell. Until near the end of my cruise waiting for a light the car just died on me. I had to put the pedal to the floor and crank the starter for 20 seconds to get it going again. At the next light, it happened again. Then at the next light, it was idling fine again.

When I got it home, I looked at the float level and noticed it was all the way up at the top again. I tried backing down the needle and seat again, but the float level would not go down. I took it for a short spin around the block to use the excess fuel in the float bowl, and the level still didn't go down.

Does this sound like a stuck open needle and seat to you?
 
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I have a Performer Mech. Fuel pump that says it does not need a regulator, as well as an autometer fuel pressure guage that says my fuel pressure is between 6 and 7 psi, so I don't think it's pressure either.
 
Instead of removing the needle and seat trying blowing (or introduce low press air) in the inlet side - if the needle and seat are working you shouldn't be able to get any air past them.
 
Is the fuel pressure measurement you are reading flowing or "deadheading"? Also are you running any type of bypass and what is the pressure at the pump? Where is the regulator located in the system? and have you done a flow test? For some reason your floats are getting pushed up, but if they are fuel should be flowing from the fuel bowl vents...

Ron