Can a stock fuel pump put out TOO much pressure?

[Kern Dog]

I have a strange situation here.
This isn't a question that is A body specific so posting here should be okay.
I have a stock 360 in a Duster, it has a Weiand 4 barrel intake and a Holley 600 single feed VS # 1850 carb. The Holley was rebuilt a couple of years ago but the car has been sitting.

This car will start and run, but within moments the engine starts to sputter and fuel starts puking out of the vents, then out of the boosters.
Float level too high?
I adjusted it and it still does it. I pulled the carb apart, soaked it awhile, blew out the passages and put it back together with a new power valve and needle valve.
It still puked fuel. I tried another carburetor, a Rebuilt ThermoQuad. Yeah, that one pukes fuel too.
I have no gauge to test the pressure but the inline fuel filter isn't getting full or bulging, it looks fine.
I'm going to try another carburetor on this engine tomorrow, maybe the one from Jigsaw. I know that one is fine.
This is weird though. I've never dealt with this before.

 

[toolmanmike]

Yes. I have seen over 10# from a stock mechanical pump.

 

[R413]

Did you remove and inspect the needle and seats? Anything small stuck in there will do this.

Yes a stock fuel pump can put too much pressure.

 

[Kern Dog]

With the Holley, I pulled the needle and seat and replaced it.
The ThermoQuad does the same thing.
At least a year ago, I wasn't getting fuel up from the tank so I went to the shed and grabbed a shiny looking pump and swapped it in. I have collected parts from friends and acquaintances for years and often times, I don't remember where a lot of this stuff came from. I don't recall any special markings on this one to denote any high volume design.
I have a few other cars here with Holleys that all run great. I can pull carburetors off of any one of them to test on the Duster.
It was 111 when I was out there working on the car. Usually I think of trying parts from other cars but maybe the heat was getting to me.

 

[Rusty knuckles]

I believe holley has a little o-ring on the needle and seat assembly that is prone to failing especially after sitting. I don't know anything about thermoquads.

 

[hunt2elk]

I had several Carter 6903 fuel pumps putting out 11 psi several years ago. At the time it was a well known issue. Don't know if they ever did get it resolved.

 

[moparedtn]

I had several Carter 6903 fuel pumps putting out 11 psi several years ago. At the time it was a well known issue. Don't know if they ever did get it resolved.

They did. I bought one from Mancini a few years back and it's on Fred ever since, running a steady 5-6 psi
according to the gauge I have on the line.

So...the answer to the OP's question is of course "yes" - but you won't know for fact until you put a gauge
on it.

 

[451Mopar]

I too have had a bad O-ring on Holley needle and seat assembly.
As for fuel pressure, it can be a problem. I have seen that at about 9-psi, the aluminum armed floats will bend. The brass arm floats seem to be stiffer.
Noticed this on a Six Pack where I think the end carbs had the nitrophyl aluminum arm floats and the center carb had the brass float. The end carbs would keep going out of adjustment, but the center was fine. Maybe this is more of a side hung float problem? I believe the Holley 600 VS single feed uses the side hung floats?

 

[lewtot184]

The only stock two valve pump I know of that is high pressure is the hipo 440 pump. All the others should be around 3-5psi. Get a gauge on it for test so you'll know exactly what you have.

 

[dfrazz]

Really need a gauge on it to accurately answer your question. Otherwise you are just guessing.

 

[DanielSlocum]

Perhaps if the fuel tank vent happens to be plugged fuel pressure could go up?

 

[Curiousyellow71]

Pressure gauge is probably next or your just guessing. It sure sounds like to much pressure.

 

[ckessel]

Does the carb have brass or the plastic/foam floats? The foam floats get attacked by alcohol over time. Brass does not. Or if already brass, maybe a bad seam etc letting fuel in and therefore not floating.

 

[furious70]

Since you've used 2 carbs probably psi related.

I'll make you feel better by saying I have one proform body Holley that I have never been able to keep from intermittently doing this. Even swapping bowls off another carb that works fine. I have no explanation for it.

 

[Kern Dog]

Does the carb have brass or the plastic/foam floats? The foam floats get attacked by alcohol over time. Brass does not. Or if already brass, maybe a bad seam etc letting fuel in and therefore not floating.

The front float is the black foam, the rear is brass. They both floated well in water.

 

[BSB67]

KD. Put up a pic of what you are calling a “stock pump”.

 

[RJRENTON]

Yes. I have seen over 10# from a stock mechanical pump.

The maximum pressure that can be developed is limited to the diaphragm area and the spring pressure that pushes on the diaphragm. The push rod or lever arm operates the diaphragm via the spring. The pump is a positive displacement design. At ZERO FLOW pressure will maximum, limited by the pressure spring...the pump's volume is detetmined by the diaphragm area. Its not quite a linear relationship between pressure and volume.
BOB RENTON

 

[PRND21]

KD, I believe khryslerkid had a thread about this very subject a couple of years ago.
BTW, nice Duster.

 

[Kern Dog]

Thanks again, guys.
To remind, this is a stock appearing pump in a 360. I'm going out back in a few minutes and will have more info soon.

 

[BSB67]

Does it look like this:

Or this: