So I have a carbed 5.0 in my ranger. All the work was done by the previous owner. It has been running fine up until the other day, when it started bogging like its running low on fuel. I added gas and it hasnt started since. So me being dumb I bought a new fuel pump (forgetting it has an aftermarket fuel pump down the line) so all that time and money was wasted because it did nothing. I wasted more time trying to trace out why it has no voltage to the fuel pump connector, nothing to the relay, same with the inertia switch (all because it was bypassed for a different pump). So I crawl down there and see the inlet hose (coming out of the factory fuel pump leading to the aftermarket pump) is bone dry (I can see that through the glass fuel filter housing), but farther down the same line there is another filter that leads straight into the regulator, which for some reason makes bubbles and even fills up the filter a little bit. That leads me to believe it is getting pressure through the oulet tube somehow, but I could definitely be wrong. So my question is 1: why would I be getting no fuel through the inlet but I see fuel down the line in the same inlet tube near the regulator side? (and no there is not leftover fuel in the line from when it ran because it all drained out replacing the aftermarket pump) and 2: what could have caused/ be the cause of me getting next to no fuel pressure all of a sudden? I have replaced the aftermarket fuel pump (because I ran the previous one dry trying to get it to start to the point it seized). I made sure the inlet line was not clogged (and the factory pump is brand new so it should be sucking fuel just fine). Yes I also have an adequate amount of gas. Anyone have any ideas? I'm assuming the aftermarket pump is sucking fuel through the oem pump off of pressure because idk how else it would work

 

Welcome to the forum

Can you make a simply line drawing of the fuel system

Gas tank------------------filter-----external fuel pump----------pressure regulator----------------carb

Is there a Return fuel line on the pressure regulator?

Is there a pump in the tank?



A word about fuel pumps
Diaphragm fuel pumps, like the old style mechanical pumps on the engine can create SUCTION to pull fuel out of a gas tank, i.e. from bottom of tank and up and over the top of the tank
But diaphragm pumps are low pressure, maybe 10psi at most

Centrifugal fuel pumps have NO SUCTION, most electric fuel pump are centrifugal style, these can do up to 80psi output pressure so used with fuel injection systems
So an IN TANK electric pump is fine since its sitting in gasoline it doesn't need to suck in gasoline
An external centrifugal pump won't work, unless another in tank pump feeds it fuel, it can't suck fuel out of the tank, well up and over the top, if you drill a hole in the bottom of the tank it would work, lol

On a carb V8 you could use just one low pressure electric pump inside the gas tank and then a filter and then to the carb, but they are expensive usually

 

@RonD thank you for the detailed reply! You were right about the external electric fuel pump not having enough power behind it to pull the fuel up and out of the tank. I ended up getting it to work by force priming the pump with a shopvac and after that is has worked perfectly! I also took out the oem pump and just ran more fuel line to droop to the bottom of the tank and cut up the new filter off the bottom of the oem pump and zip tied it around the line to make it work. All is great now and it's running better than ever

 

@RonD one thing I should ask though: there is a return line going back to the tank, the previous owner left the plug on the bottom of the return line (on the oem pump) and I went ahead and did that again. It runs great the way it is but im almost wondering if it would be better if I took that cap off. What would be your opinion on that?

 

Yes, what you did is create a Siphon in the fuel line from inside the bottom of the tank to the outside where the pump is slightly lower than the bottom of the tank
Works great until fuel in the tank gets too low or if you go around a corner and the fuel line at the bottom of the tank is exposed to air as the gas sloshes around
So heads up on staying above a 1/4 tank

The return line is only needed if there is a Fuel Pressure Regulator(FPR) used/needed

Carb's float bowl needle valve can hold back pressure up to about 20psi, above that and fuel pressure can cause carb to overflow
If your electric pump is a low pressure model then no FPR is needed

FPR allows a fuel pump to run at maximum efficiency, lowest AMP draw, so least wear, over its life
So if you have an electric pump with 80psi out pressure and you only want 10psi out, you install an FPR with return line, between pump and engine
The return line allows 70psi pressure, and fuel, to go back to the tank
So pump can still run at max efficiency but carb only sees 10psi

 

@RonD I do have a FPR but im not sure what it is set at, and this pump is just an edelbrock 4-7psi right off the shelf at oreilleys. There is a return line, so would you suggest I open it up, or leave it be since it works fine? It's been running just like this ever since I bought it and God knows how long before. And yes I definitely know I need to keep it well filled at all times or it will lose the siphon effect

 

If fuel pump is rated as 5-7psi then FPR was not really needed, and no return line is needed, leave it as is

 

@RonD thank you sir! Have a wonderful night