Fuel pressure on 1968 440

[johnjjo]

Hello guys, cant figure out my fuel problem. I have new mechanical pump that been seating for a long time and original carburetor that was send for rebuild. also i install glass in line fuel filter right by the carburetor,  its usually half full when its running. So problem is that if i let it seat for a half a day it takes forever to start. whats happens that fuel leak down to the lowest point and then its takes for ever to pump it up back to carburetor, what is the problem?? isn't fuel pump supposed to have check valve so i wouldn't leak down like that??...
i test pressure and it showing me that it between 1 and 2 and gauge needle jumps, some time it reading between 2 and 2.5 also jumps. im using vacuum and fuel pressure gauge that i got it from year one, its brand new!
thanks for reply.

PS.
Picture of glass filter only stays half way now. This picture was taken when my electric pump was connected as well. Yes I do have a electric in-line pump under the car as a secondary. but now i keeping it off and use only mechanical

[69wannabe]

You may have a faulty fuel pump or the fuel pump push rod may be worn. The pump rods do get worn and will cause lots of fuel pressure issues. I have fixed several fuel problems by replacing the fuel pump push rod.

[johnjjo]

You may have a faulty fuel pump or the fuel pump push rod may be worn. The pump rods do get worn and will cause lots of fuel pressure issues. I have fixed several fuel problems by replacing the fuel pump push rod.

thank you
but what u think about pressure? what pressure supposed to be with this carburetor.
and is it hard to replace push rod??
Thank you

[ErikH]

I agree with the fuel pump push rod diagnosis.  I banged my head against my garage floor for a long time out of frustration due to a very worn fuel pump rod.  Remove fuel pump and look in the hole, you should see the stub of the rod.  Pull it out with some thin pliers.  My old one was worn 1/2".

[johnjjo]

I agree with the fuel pump push rod diagnosis.  I banged my head against my garage floor for a long time out of frustration due to a very worn fuel pump rod.  Remove fuel pump and look in the hole, you should see the stub of the rod.  Pull it out with some thin pliers.  My old one was worn 1/2".

i will definitely check rod but what about pump it self, what pressure i need and why would fuel drain down the hose while it seats like that, isn't return stop valve supposed to be in pump??
Thank you

[BLK 68 R/T]

Factory spec for a 68 440 HP is 6 to 7.5 lbs of pressure. The drain back you are experiencing could just be today's bad fuel evaporating or boiling out of the carb and the fuel line after you park it with a hot engine. Do you have a return line installed?

[myk]

Agreed.  Today's modern fuels do not play nicely with our cars.  I would check the fuel pump pushrod, but I would also look into a return line system if you don't already have one...

[c00nhunterjoe]

Mechanical pumps are not designed to pull fuel through an electric pump that is shut off.... huge restriction. If you are not going to use the electric pump, then bypass it and rerun you pressure test.

[BLK 68 R/T]

  definitely a good idea 

[Troy]

Mechanical pumps are not designed to pull fuel through an electric pump that is shut off.... huge restriction. If you are not going to use the electric pump, then bypass it and rerun you pressure test.

Depends on the type of electric pump. But most of them, you're correct.

Troy