Electric fuel pump with carb OK?

[68 Sport Satellite]

I'm running an Edelbrock 600 manual choke carb right now with stock fuel tank and new carter mechanical fuel pump. In parallel I'm in the middle of my 451 stroker build, which will eventually have EFI. In preparation for the new motor install, several months ago I purchased a brand new stock dimension fuel tank from Hot Rod City Garage, complete with internal baffling, sump, and in-tank electric fuel pump. I plan on swapping in the new tank when I put the new motor in. This will also allow me to delete the mechanical fuel pump up front, making room for my down-low location of the new Buchillon A/C condenser when I add A/C to the car after the motor is in.

In the meantime, is there any downside to running my new fuel tank with in-tank electric fuel pump while running a carb? Will it give me better cold starting even without EFI?

What about if I leave the mechanical fuel pump in at the same time? Can I also do that? I currently have a diaphragm type Mr. Gasket fuel pressure regulator with fuel gauge and have it set to 4.5psi. When I install the new fuel tank I plan on using the new Aeromotive fuel pressure regulator that came with the tank, also dialing down to 4.5psi.

 

[Seax440Dodge]

nope, no downside, just make sure your fuel pressure is low enough that it doesn't blow fuel past the needle


as far as cold starting, no, I don't think it'll help with that (as far as the carb is concerned, it's still just fuel getting pressurized and sent to it)

 

[67 coronet]

i would check with the fuel pump manufacturer to make sure dialing down the presure that much wont damage the pump.most efi systems use over 45 psi.

 

[Meep-Meep]

As long as the fuel pressure is at 7 PSI (carb pressure) you will be fine. However, depending on your pump, it may require you bleed off some of the fuel back to the tank to get the pressure to the point the regulator can deal with it. if the tank pump is 25 PSI that might be too much for just a regulator, so run a return line (you will need to anyway) then put a Holley jet as a restrictor to get the pressure down before you hook up to the regulator. This is the cheap temporary method until you get EFI.

 

[scotts74birds]

An adjustable fuel pressure regulator with a quality gauge should be mandatory. Holleys like 4-6 lbs. Others prefer 7-8lbs. I would NOT use the EFI pump on the carbed motor, and try to choke it down with a regulator. Asking for problems. Till you do the EFI conversion you want, just use a mechanical pump with a regulator. Cheapest and easiest.

 

[dpstark2]

If they used a good pump, you'll be fine as long as you have a return line. What you don't want to do is dead end the system with a regulator acting as a brick wall for you fuel supply when pressure gets too high. That can and will eventually damage a pump that is not designed for that type of operation. Virtually all EFI systems use a return, though some actually regulate pressure and volume through the computer and a controller that man-handles the pump directly.

I have my in-tank pump that puts out 90 psi dead ended- with a regulator and return the carburetor is quite happy. And no, I haven't made any further EFI progress... Yet.

The only issue I've heard of is people massively over-supplying their system such that virtually all fuel is constantly circulated, which can lead to heat and eventually boiling in the tank. Not good... You're highly unlikely to have that beefy of a pump.

 

[68 Sport Satellite]

thanks for all of the great feedback everyone!

I already have a return line, so that's one less thing to worry about...

I believe my in-tank pump is rated to put out > 70psi, not sure on the exact #.
I mainly wanted to install the new tank sooner than later so the new motor has a fresh, non-corroded fuel tank. Maybe I'll be fine with my old tank until the EFI switch is ready to go? Although, dpstark2 says he's having no trouble.

 

[Photon440]

One thing to keep in mind is making sure your mechanical pump is in good condition. If the diaphragm springs a leak, the electric pump behind it will happily keep pumping gas past the leak and fill your block with fuel. Yours being new shouldn't give you any worries.

 

[dpstark2]

To be clear, I am not running a mechanical fuel pump in addition to electrical. I guess you could, you but you probably need the return to come off before the mechanical pump. Regardless, I don't see the point of having both. Just remove the mechanical and block it off.

Pressure is a result of restriction, so a pump doesn't put out 70 or 90 psi unless there is a restriction somewhere (carburetor seat, pressure regulator, or a dead end). What tends to hurt pumps like this is when there is no way to pass gas (yeah, laugh at that one... go ahead) and the internal bleeds on the pump are forced to overwork. At least, this is my understanding. Still, plenty of people have run dead end systems without issue for years. No sense in fooling with that if you have a return ready.

I was shocked to learn that my beater commuter uses the computer as the pressure regulator- it modulates the pump electrical supply and monitors the fuel pressure gauge to control fuel pressure. Seems a bit hoaky to me, but I guess it saves a buck and it's worked fine for almost 200k miles.

For what it's worth, I have found the electric pump to be a worthy upgrade to a carbed car. It has helped with what I perceived to be some fueling issues and definitely helps with the fuel evaporation issue as the car sits all week. In the future, I'd skip all the fuel tank fab work and drop in one of the new Aeromotive Stealth units.

 

[68 Sport Satellite]

The fuel evaporation issue after sitting all week is what I was hoping to improve! I may just go ahead and get that fuel tank installed then even before the big block is done. One more thing out of the way. I have never done that before and may enlist your help for safety sake. The tank is ready to go and it would be fun to get your feedback on how it ends up comparing to your setup.

To be clear, I am not running a mechanical fuel pump in addition to electrical. I guess you could, you but you probably need the return to come off before the mechanical pump. Regardless, I don't see the point of having both. Just remove the mechanical and block it off.

Pressure is a result of restriction, so a pump doesn't put out 70 or 90 psi unless there is a restriction somewhere (carburetor seat, pressure regulator, or a dead end). What tends to hurt pumps like this is when there is no way to pass gas (yeah, laugh at that one... go ahead) and the internal bleeds on the pump are forced to overwork. At least, this is my understanding. Still, plenty of people have run dead end systems without issue for years. No sense in fooling with that if you have a return ready.

I was shocked to learn that my beater commuter uses the computer as the pressure regulator- it modulates the pump electrical supply and monitors the fuel pressure gauge to control fuel pressure. Seems a bit hoaky to me, but I guess it saves a buck and it's worked fine for almost 200k miles.

For what it's worth, I have found the electric pump to be a worthy upgrade to a carbed car. It has helped with what I perceived to be some fueling issues and definitely helps with the fuel evaporation issue as the car sits all week. In the future, I'd skip all the fuel tank fab work and drop in one of the new Aeromotive Stealth units.