Re-doing fuel lines

**04SilveradoMykk** · 04-21-2011, 09:34 AM

Hey Guys,

It was recently brought to my attention how inefficiently my fuel system was set up. So todays project will be to re-plumb the fuel lines for a more efficient fuel delivery at high RPM. What better time than while the bed is off the frame.

#1 is how I had my lines ran, #2 is how they will be run.

My first mistake was running the pressure regulator so far back, my second mistake was using this crappy 'performance' isle fuel filter. I can hardly even blow through the clean filter. I have a feeling this was the culprit to my drop in fuel pressure (8psi at pump, 2psi at carb) I'm replacing the low flow fuel filter with a NAPA 3270 rated at 140 micron, considered a course filter it will flow very well and will be in-line between the cell and the pump.

With the Mallory 4309 pressure regulator mounted by the carb, I can run manifold vacuum to the regulator and momentarily decrease fuel PSI at idle (better for the needle & seats) and increase as much as 5psi fuel pressure for WOT (no manifold vacuum). I also intend to run the regulator parallel to the carb T'd off the main fuel line instead of feeding the carb through the regulator. This should insure max potential fuel supply to the carb instead of getting sent back to the fuel cell.

Once I'm certain the carb is getting the fuel necessary I can spend more time dialing in the carb's fuel curve.

Making sure the fuel system is adequate and supplying enough fuel for the application can resolve several high rpm power output issues. Especially if your seeing a lean situation

Cheers ~Mykk

**04SilveradoMykk** · 04-21-2011, 03:49 PM

I just swapped out the Carter P4070 electric fuel pump (72gph @ 6psi) for a Carter P4601HP (100gph @ 14psi), I have the pump deadheaded at the carb without the fuel pressure regulator and I'm getting 9psi at the gauge on the carb and the fuel isn't forced past the needle & seats.

This might be the solution to my problems. Also, I took the inspection plate off the P4070 and found the pump packed full of shavings from the foam inside the fuel cell. That would most definitely create a fuel delivery problem at higher rpm. I'm going to inspect the sump of the fuel cell and see if I have a clog there too that could explain only 9PSI being delivered from a 14 psi pump. If I do get the full 14psi I'll need to install the pressure regulator again.

**91vortec** · 04-27-2011, 04:09 AM

run a high micron filter before the pump and a cheeper one before the carb. what size of hose you gonna run?

**Koots** · 04-27-2011, 04:35 AM

How much did that 4601HP cost you?

Looks like it could be a good candidate for a replacement lift pump for my diesel. max pressure going into the injection pump is around 14psi, but anywhere from 8-10 by the time it crosses 2 fuel filters (spin on style), which it sounds like this pump could be able to do. Right now i'm using a cheap replacement pump that's probably putting out closer to 4psi by the time it gets to the pump.

**04SilveradoMykk** · 04-27-2011, 09:15 AM

Originally Posted by Koots

How much did that 4601HP cost you?

Looks like it could be a good candidate for a replacement lift pump for my diesel. max pressure going into the injection pump is around 14psi, but anywhere from 8-10 by the time it crosses 2 fuel filters (spin on style), which it sounds like this pump could be able to do. Right now i'm using a cheap replacement pump that's probably putting out closer to 4psi by the time it gets to the pump.

plugging the 4601hp in google turned up a good amount of diesel forums, it looks like most guys use this pump as the lift pump. The 4601hp is $120 through Summit and $150 on the shelf at the local NAPA