Technical HELP PLEASE Fuel pressure problem

First post...new to the HAMB So this has been an ongoing problem. I am running a carter p4070 electric about a quater of the way away from the tank on the Olds in attempt to solve vaporlock related problems. Im still running though the stock mechanical pump and also using a holley byp*** fuel pressure regulator... Ok heres where im stummped... So the guage reads somewhere around 4 ish psi as to be expected right? I then regulate the pressure down to about 3 pounds becuase thats what the rochester carb likes... Heres the stump... I drive the olds around the block a few times and the guage reads zero... No pressure at all... The engine is still running however and even if i regulate for a higher pressure i still get nothing at all... I can even pinch off the return line completely and still nothing... No pressure at all...but after i let it sit for awhile and it cools down then the cylce of pressure no pressure repeates itself... I am running a filter before the carter and it is getting sufficent power...and the gas tank is properly vented... Hambers Please help ! I am completey stumped

 

bad gage?

 

No becuase you can feel that the rubber line is easily squished

 

did you try to pinch both lines and watch the gage?

 

Sock in tank @ pick up ?

 

I can pinch both lines and the pressure will go up but just for a moment... But thats just becuase im squeezing pressure up

 

So here is how things work. Your gauge can only show pressure, if your needle isn't seated to stop fuel flow into the carb it isn't making any pressure. I've found that most carb's like 7-9 lbs of pressure so I'm thinking your running on low fuel in the carb keeping your pressure from coming up on the gauge. Just cap the feed line and see what happens on the gauge. 3-4 lbs is for old Flathead's not your Olds.
The Wizzard

 

It doesnt have a sock... justa straight tube

 

I have pinched the line between the carb and regualor and still get zero

 

Shoulnt the guage read pressure when the guage IS seated ?

 

You must have a closed system to measure the pressure. At 4 lbs you may not be pushing fluid past the stock pump.

 

Just byp*** the stock pump and see if your issue goes away.

 

So like a low float level ?

 

Re thinking here. Pull the line just ahead of the electric pump. Put the regulator on the loose end and drop a hose into a can. Turn it on see what happens. New don't always mean good.
The Wizzard

 

This was going to be my next step

 

Thought of doing the same thing

 

Float level would be correct but not getting enough volume to fill the bowl.

 

As I'm also considering monitoring my fuel pressure ... what mfgr and range gauge are you using? How much was it? Dry or liquid filled? Where is it plumbed in?

 

Keep the basics in mind when troubleshooting a problem. Pressure results from a restriction to flow. Pumps create flow, not pressure. When the flow hits resistance it results in pressure. If there is not pressure there is either a lack of flow, or a lack of resistance to flow, or a combination of the 2.

 

I didn't see mention of running or drivability issues.

Sounds like you might be chasing ghosts in the fuel system.
Those guages are notorious for reading wrong because of heat. Read up on it . there's a purge ****on on the better ones to get correct pressure readings as temp changes

 

Might try an inline gauge right after the electric pump

 

I've had the same problem for quite some time now and I still not sure if I solved it yet or not. I running 3x2 Stromberg My last fix


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Ooops the fuel inlet hole is about .100 on each carb so .100 x 3 = .300 total. I backtracked the fitting and found a few were like .180 thousands so I opened them up to at least.325 thinking I was starving the carbs. I'm still not sure if I fixed the problem yet. Just need time and I'm running out of weather here in the northeast.


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Had the same symptoms on my coupe. it had a Mallory gauge. final changed the gauge, no more problems. just my experience, not saying it is for sure your problem. only way to be sure is to try another gauge. if the vehicle runs ok, I would try another gauge.

 

If it is not the guage, you have a volume issue.[The engine is drinking more than the pump can supply]
Usually it's before the 1st pump.
Byp*** the filter that is before the Carter electric pump and try it again. And check for any blockages in the fuel lines Including screen filters in the tank.

Pressure is pressure and Volume is volume

 

Does the car run differently when gauge has a pressure drop?

 

If you brought your Car to me to fix I'd tell you up front you have to much Junk in the Fuel system. Make a choice, stock pump or electric. Band-aids are a headache and that's what you have currently.
Filter before the electric is good for a blockage and fuel starvation. Pull the line at the Carb, put a hose
on it to a catch can. Pull all the plugs, spin the motor and see what you have. Stock worked fine when it was new so I'd head back to that. If you want a filter put it between the Pump and Carb where you can get to it. Go to NAPA and buy a coil of 5/16 steel line and replace the stock line in one piece from tank to Pump. Make sure you don't have any place where the exhaust is heating the line. To many fittings, to many places for restriction. Most br*** fittings for 5/16 flair nuts are less than 1/4" id.
The Wizzard

 

In my experience running stock mech setups usually lead to vapor lock problems becuase of the higher vapor pressure of newer fuels

 

I'm not sure I'd buy into your belief however I'd go forward with that point of view for you as a Customer. I'd pitch the Mech pump and build a stand alone electric pump system. One or the other not a combination of both. That method clearly is not working for you.
To clear up why I think the way I do about "newer fuels" of today. In my personal case and the fact my Avitar now has near 40K miles on it. It burns today's pump gas with a stock manual pump and a Carb. I have never yet had a Vapor lock issue. My bone stock 59 Ford same thing. If new fuels were subject to causing this issue alone I probably would have delt with it by now, or at least had someone come to me for help.
The Wizzard

 

Have you driven through 100 plus degrees traffic with out any problems?