fuel issues
Post Fiend
Joined: Jan 2001
Posts: 5,121
Likes: 1
From: Springfield, VA
You didn't say if its a mechanical or electric pump, or where it's located. Also are you running an inline regulator anywhere? I need a little more info to help diagnose your problem. A common thing if it an electric pump located back near the tank is that if you run it to a dead headed regulator, the pump will get hot and die. When it cools, you get fuel feed again until the pump gets got again and it looses pressure. Just a thought.
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Elder User
Joined: Aug 2004
Posts: 620
Likes: 1
From: NE Wisconsin
mech. pump in stock location, no regulator. No hoses pinched or kinked,and all new. Hard lines newer in stock locations. I get fuel to the hard line connected to the low press. side of the pump when it acts up. If it is plugged, its between the tank diverter valve and the fuel pump. I haven't had time to look at it yet. Should be doing it now but I want a few ideas.
However, my hard lines look like what the quote in my sig. says. Been that way a while working fine though.
However, my hard lines look like what the quote in my sig. says. Been that way a while working fine though.
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Posting Guru
Joined: Mar 2006
Posts: 1,213
Likes: 0
From: Parma, MI
How about the carb inlet? Have to screw it out and check it. Happened to me once, full of gunk.
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Elder User
Joined: Aug 2004
Posts: 620
Likes: 1
From: NE Wisconsin
that would fill the fuel filter though. The thing that makes me wonder is the high load/high vacuum condition that causes it. Secondarys open and power valve opens=way more fuel required. Anything there spark intrest?
Post Fiend
Joined: Jan 2001
Posts: 5,121
Likes: 1
From: Springfield, VA
I just went through this issue on my Uncles 79. He has a 460 that ran well in the winter time, and as the weather got warmer, he would spit and sputter and be fuel starved. We ended up putting a small electric pump back near the tank to help keep up with the demand that the motor needed. If you said the pump had worked well in the past, your pump may be dying out and not pumping enough fuel when it gets hot. As a quick and easy test. run a temporary line to a 1 gallon tank that is near the pump, start the truck up and let it get warm. Idle it up and watch what happens to see if it starts to suck the filter dry. If you don't see a problem there, next thing is to check your lines or your sump. Possible you got trash in the tank and during times of high demand it just coincidentally clogs the sump.
Post Fiend
Joined: Jan 2001
Posts: 5,121
Likes: 1
From: Springfield, VA
If it's a mechanical pump, then a "high vacuum" situation on the motor would not have any effect on the pump. It is operated by a shaft that goes from the pump to the eccentric on the front of the cam shaft, not vacuum. What I was referring to about the pump dying out was not a heat issue, just the pump itself going bad. They vanes inside the pump may have a crack that expands when the heat of driving are there. Mechanical pumps had their day, but I prefer the simplicity and ease of an electric pump. 2 Wires to the ignition switch circuit, an inlet and outlet lines, and a return line regulator to make the pump run more efficiently and cooler. Nothing better!
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Elder User
Joined: Aug 2004
Posts: 620
Likes: 1
From: NE Wisconsin
Yeah, I know how the pump works. The high vacuum I was refering to,(should have been low manifold vacuum) would open the secondarys and the power valve for more fuel into the main system of the carb. Hate to go buy an elect. pump if I am not sure of the problem. Kind of think it's the pump though.
Return line regulator? What return line?
Return line regulator? What return line?
Post Fiend
Joined: Jan 2001
Posts: 5,121
Likes: 1
From: Springfield, VA
It's mainly an electric pump thing where the pressure from the pump needs are regulator. Most people just run a dead head regulator between the pump and the carb, this causes the pump to run hot over time and eventually will burn out. The solution is to run a return style regulator that will do the same job as the deadhead style, with the added bonus that the un-needed fuel that would just sit in the line getting hot, is recirculated back to the tank. The result is the pump will run cooler and more efficient and your fuel temps will be lower as another result. I've posted this before, but check here for more info:
Century Performance Center, Inc. :: Fuelish Tendencies - Understanding Fuel Pressure and Volume
Century Performance Center, Inc. :: Fuelish Tendencies - Understanding Fuel Pressure and Volume