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Can someone explain how I should setup the fuel system on my L83 swap

73K5BlazerSS

73K5BlazerSS

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I'm ready to install new 3/8 fuel lines on the inside of my frame rails. Aeromotive has a Phantom pump system that looks nice and will run PWM like the factory. The company making my harness says I don't need PWM... just get an intank pump that sends 72 psi. Aeromotive says that it won't idle properly and the pump won't last long without PWM.

Let's say I go with the Phantom pump with PWM. I can see 2 fuel lines on the left side of my trans where they were cut during the pull out. I assume these are my feed and return lines. Where do I run the tank vent line? Does this go up to the intake ?

Is PWM necessary or am I just getting into more time and money with little benefit?
 
Are you running something else besides the factory ECM?
 
I had to buy an ECM from the company making the harness. I believe it's factory with some sensors deleted. I'm not sure if that answers your question. I'm new to this swap stuff.

If you're talking about being tuned beyond stock for high performance then no.
 
On the swap I did, we ran a ep381 pump in the stock ‘87 up sending unit. It runs to a corvette filter/regulator that returns to tank. Single outlet to engine. Pwm isn’t necessary.
 
Probably factory computer. I’d let it PWM if it wants.
You need a vented tank, back to a charcoal canister is best
I prefer a return to the tank
 
Fastereddie said:
On the swap I did, we ran a ep381 pump in the stock ‘87 up sending unit. It runs to a corvette filter/regulator that returns to tank. Single outlet to engine. Pwm isn’t necessary.
Click to expand...
Do you have any issues at start up or idle? How long has the setup been in operation?
Did you run a vent to a charcoal canister in the engine compartment?
 
No it runs great. It’s been together since august of ‘19
 
Bent77 said:
Probably factory computer. I’d let it PWM if it wants.
You need a vented tank, back to a charcoal canister is best
I prefer a return to the tank
Click to expand...
Where would I run the purge port on my charcoal canister? To the intake? Will I need a purge valve and relay for the L83 motor as well?
 
You need to make sure you have a good return line so you don't burn the pump up, if Aeromotives pump says it needs PWM, get a pump that doesn't. I sell the Walbro and Holley pumps that go in the stock sending unit and supply plenty of fuel without needing PWM. I also sell the Aeromotive if you want that one. Which one exactly is it, I can check into the PWM requirement.

Holley can also run the L83 and DI with the Terminator X if you need, I can get those too, they will also run a 4L60E, or 4L80E, but not the 6, 8, or 10 speed at this time.

To sum it up, PWM is not necessary for what you are doing unless you put a pump in that needs it to stay cool, or you don't run a large enough return style regulator.
 
folkenheath said:
You need to make sure you have a good return line so you don't burn the pump up, if Aeromotives pump says it needs PWM, get a pump that doesn't. I sell the Walbro and Holley pumps that go in the stock sending unit and supply plenty of fuel without needing PWM. I also sell the Aeromotive if you want that one. Which one exactly is it, I can check into the PWM requirement.

Holley can also run the L83 and DI with the Terminator X if you need, I can get those too, they will also run a 4L60E, or 4L80E, but not the 6, 8, or 10 speed at this time.

To sum it up, PWM is not necessary for what you are doing unless you put a pump in that needs it to stay cool, or you don't run a large enough return style regulator.
Click to expand...
I got an L83 with the 6L80 it was mated to so I guess the Holley is not an option.

What would my setup be with an intank pump using the stock sending unit?

1 - Walbro pump with a 3/8" line out to a regulator
2 - 3/8" return line back to the tank from the regulator
3 - 3/8" supply from regulator to fuel rail
4 - 3/8" vent from tank to charcoal canister?

Sorry for all the questions I'm so confused from researching the internet.
 
73K5BlazerSS said:
Where would I run the purge port on my charcoal canister? To the intake? Will I need a purge valve and relay for the L83 motor as well?
Click to expand...
The L83 evap valve is right behind the throttle body. ICT billet makes a nice little block off plate if you choose not to use it. If you do plan to use it, make sure your harness builder knows that.
 
If you are keeping the charcoal canister then leave it hooked up the same way it was stock.

Normally I recommend the fuel go through the rails and then into the regulator, and then back to the tank. However, with the GDI motor you would need to return the fuel to the tank with the regulator before the high pressure pump(since the high pressure pump doesn't have a return), and supply the pump with the high pressure side of the regulator.

With a return style regulator, and the correct pump, you won't need to run PWM. But you can if you want.
 
Thank you for that picture fastereddie. If you block off the vent purge what did you do for a tank vent? Vented gas cap or a short hose with a rollover vent valve?
 
73K5BlazerSS said:
Thank you for that picture fastereddie. If you block off the vent purge what did you do for a tank vent? Vented gas cap or a short hose with a rollover vent valve?
Click to expand...
There is the big fill vent, then the small vent that would run to the charcoal canister. On this particular rig, the canister is gone and just vented to atmosphere somewhere.

F10203F1-920A-46F7-B27E-E783B41DDD3B.jpeg
 
Thanks again... I can always understand much better with a picture.

I'm going to get the same sending unit that came in the EFI K5s. I'm thinking about making a similar access hatch in my truck. I might just use a section of floor pan and rivnut it in place.
 
73K5BlazerSS said:
Thanks again... I can always understand much better with a picture.

I'm going to get the same sending unit that came in the EFI K5s. I'm thinking about making a similar access hatch in my truck. I might just use a section of floor pan and rivnut it in place.
Click to expand...
It you have a welder, you can make a small frame around the hatch for the plate to lay on, with the riv nuts in the corner.

pay attention where you cut it so that you can access all the fittings and hoses as well as the pump
 
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