For starters...I also agree that it has been enjoyable to discuss lift pump theory to the max. I think I might have to try a walbro myself when or if my Holley Blue craps out. I have 50k on my current lift pump system (Scotty Smart Fuel Fittings with Holley Blue Pump) and it has performed flawlessly. I maintain 12.5 psi at idle and cruise in the summer and do not see more than a 2-3 psi drop at extended full throttle (even cranked up to 550 hp). In the winter I see about 2 or so less psi untill everything warms up. Any ideas why the pressure would be lower???? Fuel is more viscous?

My real question for everyone to ponder is more of the plumbing of my aux tank. All of the other discussion got me thinking...

I gravity feed into a tee in the OEM vent line. It has worked great for 74k....no leaks...keeps OEM tank full till AUX tank is empty. But...I started thinking...where does the return fuel go???

Assuming there is enough return line pressure from the CP3...will it just push its way back into the OEM tank against the 2 or soo feet of head caused by the AUX tank when it is completely full? The Aux tank cap is suction vented...

Hopefully the 1 psi of head caused by the Aux tank does not have any negative effects to the CP3's longevity or performance...or will cause leaks in the return line?

Thoughts...ideas?

 

What happens if you take the fuel cap off your stock fuel tank with this setup?

Andy

 

If the aux is full...it will get you wet. If the aux is empty....nothing.

It it just like giving your OEM tank a head start...I can drive 500-600 miles before the needle moves.

 

Did you plug the two little vents on the top of the truck main tank? I did the vent rework and pluged the two vents on top of mine, don't know if it was a good idea or not at this point. I would think in the setup you have these would be leaking fuel unless it never fills those two cavities.

 

I remove the stock filler neck
gravity feed into big filler hose
extend the vent hose up to the top of my aux tank and tap into the vent on my aux tank

works flawlessly

 

Bump...

Hey Superduty...your thoughts with my concerns?

 

Back to the top....


I am starting to wonder why my lift pump pressures are varying so much with the cold???

They will go as low as 5-6 psi when it is below 15 degrees or so. It has to be 50 plus for me to see my normal 12.5 psi. The temporary drop in pressure when putting power to ground is non existant when I only have 5-6 psi and up to 2-3 psi drop when I have 12.5 psi???

I was still hoping for a Superduty response to my original psot as well.

Thanks.

 

I believe that superduty along with a few others from the heated fuel system threads were muted and/or banned. Hopefully only temporary, cause I have a few unaswered questions and had to put my Walbro retrofit on hold until he comes back,

 

You may want to post your question on cumminsforum, SD will be more likely to see it there.

 

Could it not be that your fuel is gelling a little. Had mine freeze up in -40 in minnesota last year.

 

One of the reasons your fuel presure drops when it is cold is the grid heaters turn on and lower battery volage so your pump runs slower

 

the CP3 fuel system does have a maximum drain line restriction of 2.7 p.s.i. , I would check that when you have both tanks full.