Fuel Pump vs. Carb Question...

[DukesFin]

GM L6 250cid engine with a Holley 4160 390cfm carb...

Rebuilt the carb again, re checked everything again and I see the problem...

I'm getting fuel dripping down into my intake when I'm not advancing the throttle at all...

I called Holley and they said it is from either:

Improperly set needles/seats - They are definitely good (2nd set to be sure were installed today)

Bad Power Valve - 2nd one installed today to be sure and I do have the power valve saver kit installed as well

Too much fuel pressure - NOT SURE ABOUT THIS ONE!

Can a faulty fuel pump supply too MUCH fuel pressure? I have to go get a meter, but what pressure should be good for this carb?

I thought that if the pump failed, it would stop supplying fuel or supply too little! I do have the safety clear fuel bowl and it is bone dry so I assumed the pump was fine.

Thanks in advance!

 

[riverjet502]

Re: Fuel Pump vs. Carb Question...

If I remmember correctly your needle & seat should be good for 9 psi. I have my fuel regulator set for 7-3/4 psi feeding a 4150... 850 double pumper...

 

[Bondo]

Re: Fuel Pump vs. Carb Question...

Any Carbed motor should be supplied with 4 to 6psi Fuel Pressure,......5psi being Ideal......

 

[Haut Medoc]

Re: Fuel Pump vs. Carb Question...

ayuh!.......​

 

[riverjet502]

Re: Fuel Pump vs. Carb Question...

One thing to keep in mind is that if your showing say 4-6 psi at slow speeds, will you maintain the same psi at wide open on a non regulated fuel system? Doubtful. I had a 350 that would show just under 6psi at idle and at wide open it would drop to just under 3 psi. I changed the fuel line to a braided stainless to get ride of the stock steel line and several 90 degree bends. At wide open it then only dropped to @ 4psi. Just something to think about.

 

[79Glastron]

Re: Fuel Pump vs. Carb Question...

Also, the accelerator pump may be leaking. How do you like the 390cfm 4 barrel on your engine?

 

[DukesFin]

Re: Fuel Pump vs. Carb Question...

Okay, UPDATE:

I had to go down to Summit Racing to pick up the fuel pressure regulator...

I did have enough sense to pick up another power valve since they are so cheap and even though I have one of those power valve saver kits, an extra on board never hurts...

I got home and took the primary bowl off, then took the power valve that I had installed at my last rebuild... HMMM... Something isn't right here... The new one I just got from the pro's at Summit looks different... I put the new one on.

I finally got her started (I'm having to hold the choke closed as it took a while and the choke had already heated up). I got so excited and freaked out that it started, I TURNED THE KEY OFF!

It is dark now, so I had to stop for the evening.

Tomorrow, I'll go get some new plugs and start again. The ones that are in it now have just been soaked from all of the fuel pouring into them then carbon deposits from the occasional firing. I'll clean the old ones in the morning and get her cranked up. Once I am confident she will stay cranked, she's getting some shiny new plugs!

When it is running, I love the carb. I know I'm getting better mileage with the 4bbl Holley than I would be with the 2bbl that came stock on this motor, but I'll tell you what: Holleys are a bit "touchy" for sure! Once I've got her up and running, I'll be singing Holley's praises, but for now, it is a bit frustrating.

Being 100+ degrees up here or down here by Lake Lanier in Georgia, I'd sure love to be on the water!

I'll give an update tomorrow, but for now, I have found that the power valve that came in my rebuild kit was either crap or not the right one. The guys at Summit Racing saved the day...

BTW: Does anyone need a Holley Fuel Pressure Regulator (4.5 - 9 psi)? ;-)

 

[MikDee]

Re: Fuel Pump vs. Carb Question...

I've never met a Holley carb I've liked! Nor one that didn't run too rich? My Fav is, Carter as in Carter AFB, or it's spinoff Edelbrock. I hope you got yours fixed, I'd like to hear a success story about a Holley (Ford).