Hi guys,

I am currently working on a 73' f100 that has a 6.0 out of a 2008 chevy express 3500. Right now it has an inline fuel pump, but it isn't hooked into the ecu so there's no communication there so it's runny real wacky. I've been told of a few ways to fix this. 1. Go carbureted. 2. put a higher psi fuel pump in and plumb in a return line (right now it's a returnless system). 3. Use a stock in tank fuel pump and wire it back into the system. Problem is I can't find the 2 pigtails that clip into the fuel pump. I've read a lot about the different ways to do this, including in line pumps, but I don't get how guys are getting those to communicate with the computer. Any info. would be great. Thanks.

 

Are you using a reflashed factory ECM or an aftermarket control system? Don't go carb. Kind of defeats the purpose of a late model swap in my opinion.

I'm in the process of a 5.3l swap on a '65 Chevelle for a customer. I set up the factory ECU and fuel pump the way that it was in the Tahoe the engine came from. The ECU controls a relay that then runs the pump. Looking at LT1swap.com and the wiring diagram for the '08 truck, the fuel pump is controlled by a separate module. Do you have the fuel pressure sensor and the fuel pump control module on your setup? Fuel pressure is critical on any engine. A returnless system is typically duty cycled to keep the correct pressure.

You might look at a Corvette filter/regulator if you are using the control module or not. WIX 33737 and AC Delco GF822 are a couple of options. That would only require running a return line from the regulator after the fuel pump, to the tank.

The best thing to do, I think, would be to convert to a return style system. Your pump could be a constant run that way and not have to worry about the computer running it at all. I know it will be extra work, but it does open up more options for tuning later.

In tank pumps run cooler and quieter, but if you have dual tanks that doubles expense and the complication of wiring. You could use the donor fuel pump or an Areomotive Phantom setup.

Whatever fuel pump you use, make sure it is capable of supplying at least the pressure and volume the stock unit is rated for. Again, fuel pressure is critical. Low pressure causes the computer to up pulse width to compensate. Eventually you reach a point that cannot happen any more and you get running issues, lean condition, and possible engine damage. Too high of pressure if not running a regulator will cause a compensation to shorter pulse width until it cannot. Even with a short pulse width too much fuel can enter the cylinders causing running issues, rich condition, fuel washed cylinder walls, and possible engine damage.

 

So the mechanic I last took this to thought the in line fuel pump I was using wasn't sufficient. He said that at idle the pressure was good, but when you hit the throttle, pressure would drop. So I attached a chart of the fuel pump specs that I'm running now, and then looked up the specs on stock in tank fuel pumps...the ratings vary quite a bit. From what I see, this inline fuel pump should be sufficient, but I wanted some other people's opinions. See attached.

 

Actual on vehicle measurements are helpful, not just hearsay.

You didn't say whether you have any sort of pressure regulator at the moment, or answer any of the questions I asked. I can't help if I don't have an idea what your setup is like.

Also, in all honesty, you are probably asking this question on the wrong forum altogether. Yes, the truck is a Ford, but you are using a GM engine. There will be a lot more experience with the LS engines over at LS1tech. There are a lot of guys here who won't like what you are doing because of brand loyalties. I don't care myself one way or the other. To get the most help for what you are doing though, you need to find where the experts are hiding. Most of them won't be here.