EFI fuel pump considerations

I need some help putting together a fuel system on my Magnum swap. I am using a 94 5.2 with the stock MPFI. The injectors call for 35-40 pounds of pressure. My first thought was to use a cheap Summit inline pump in the frame rail and a regulator. However, my 70 truck still has the in cab tank. Technically the pump would be below the tank by about 9 inches, however the tank outlet is nearly 3 feet above the pump. Will that be an issue?

A return line could be an issue. Do the returns have to go back to the tank? or can they tee in to the line behind the pump?

I am not wanting to get to fancy, this is going to be temporary until the rest of the truck is done and back on the road. Then I will begin plans on a under the bed fuel cell which will hopefully utilize the Rams in tank pump and regulator. This is all new ground for me!

I'd give Auto Performance Engineering a call and see how they'd handle some of those issues. I think a Walbro in-tank pump could do the trick for you, as long as you could sort out the pressure regulation. At some point, Magnums went to in-tank regulation rather than a regulator on the rail, so you COULD handle regulation back by the tank somewhere and just run the single line up to the fuel rail. A tidy spot to run a return line is to the filler tube, but I'm guessing that's entirely inside the truck cab as well. Maybe you could fab up some sort of auxiliary fuel tank that houses the pump and return line separate from the main tank. Should be plenty of room under that monster...

Clair

I asked some similar questions when I was putting in a magnum for my car.

The return thing will work. you can put a t in the line and put the return behind the pump.
However someone that does that sort of testing in real life said their studies showed a 40 percent loss of power as the fuel heated up.
So if this is just to get it running, I would not worry about it, but it will not run as well.

Get a reproduction fuel line to use as the return, it is an aid to keeping the pump and fuel cooler. Pull out your sender unit and put the pump in it in the bottom of the tank, you should be able to do this with some minor fabrication. Run the return line down to the same level.

R.

Clair, actually I started down that road already. My Magnum is a 94, which was the first year for the tank mounted regulator. I took a apart a 94 pump unit and pulled out just the pump. It easily fits into the sending unit hole. I cut 6 inches of the pickup off and used a piece of fuel injection hose and some fuel injection hose clamps to attach the pump to the pick up.

I even pulled off the connection for the wiring to feed the extra wires into the tank. The problem then was the regulator. The regulator isn't actually in the tank, it is on top of the unit. It connects with a rubber grommet in a 1-5/8" hole. The problem is that the regulator is also a filter and the filter part is about 2-1/2" in diameter and sticks up about 2". There isn't room between the tank and the cab to fit this. I am afraid the regulator might make contact with the cab and come loose.

I have also been second thinking the idea of having pressurized fuel in the cab. This is a Crew Cab, so that means the fuel connections are just behind the seat from where my kids will be. If there was a leak...

Here is another thought. The Ram had the regulator on top of the tank, so it maintained the a single line pressure over a nearly 8 foot line. My line will be about 9'-10'. Why couldn't I mount an external regulator on the frame rail, just few feet from the pump? Then the return fuel wouldn't be heated by the engine, right? Or is the fuel pump a bigger source of heat than the engine bay?

Dogdays, not quite sure I follow you. Are you describing the typical plumbing, with the regulator right at the intake, and 2 full length lines from the motor to the tank? I understand this is the typically recomended method and obviously does have advantages. But my goal is to have only one line and no regulator under the hood. Mostly because I don't want to rework that part with the new fuel cell.

I am open to any suggestions also!

Hey great to see you on here. Go to www.pro-touring.com and ask the question. There are a ton of very knowledgable guys over there that specialize in fuel injection. If any of your get the opportunity to see this mans car...it's flat out cool!

Tony
Columbia, Missouri

No reason you can't have the regulator just about anywhere you want... as you know, the Maggies run just the one line up to the rail, with little if any ill effects. What I don't know is whether or not the Maggie returnless system has a vacuum reference to the regulator, or if it just runs a straight pressure to the rail and adjusts for the flow across the injectors through the fuel calibration. If you're running OEM electronics, make sure you're running OEM specs on the fuel delivery (obviously). I thought Maggies ran higher pressures, but I can't swear about the early ones.

My system uses a return line, but it's separate from the rail:

Hard to see because all the crap being out of place, but you can see the regulator on the far side and the fuel line wrapping around to the rail. So, it's like a mix of the returnless and return style systems. Seems to work OK for now.

Clair

There is no vacuum reference on the regulator, just an outlet. The OBDI Magnums ran at lower pressure, about 35-40 pounds. When they switched to OBDII and the JTEC computer, they switched to a standardized injector across most all of the Chrysler lines, which was about 50-60 pounds.

Thank you for the kind words Tony!! Sorry I missed the show this year, it is a fun one.