btroup69

So I finally got my CTD about a month ago. Changed the fuel filter the other day and when I went to prime the system I found the lp to be completely dead. Who knows how long its been like this. I suppose the vp will soon be in the same boat. Anyway, I decided to get a carter p4601hp and a big line kit. I want to relocate this on the frame and get rid of the stock lp setup. My ? is, do I need to put a pressure regulator in this setup? If so, what is a good reg to use and what are some suggestions on the best way to plumb it in. I also want to put some kind of inline filter before the lp. Any info would be appreciated! thanx

PaulDaisy

I have read, and fully believe it, that installing a bypass on a carter pump will dramatically extend its life. It makes perfect sense: the LP in the stock configuration runs against dead stop when you first turn on the ignition. If you use a bypass, the pump will not be overstressed. I would install the pressure regulator and add another return to the tank from the fuel filter housing. (Edit: I used nylon lines for all my fuel system lines and recommend nylon for return lines. Very easy to work with, and Swagelok fittings work very well, an example is in my signature.)
Glacier used to sell a bypass regulator separately for around $30 but I don't see it anymore. You can also buy a 1/2" NPT or 3/8" NPT adjustable overflow valves from Swagelok, you will need to play with those to set pressures correctly.
-P

btroup69

Ok, sounds like I better put one in then. Thanks for the info. Do you mount the regulator before or after the filter housing, or dont it really matter? Anyone know if I can get a good regulator at like napa or autozone?

scottsjeeprolet

I don't really feel that a regulator is necessary. I run 26psi for 2.5 years and no problems.
The FP only runs for a moment before the truck starts. The VP44 has an internal bypass as well, it only uses what it needs as well as the LP.
My Holley Blue has an internal bypass as well. It came with a regulator and i didn't use it.

Hillcountry

You don't need a regulator with that pump. I've had one on the framerail now for 2 years with no problems. It runs at 12psi and drops to about 9psi when I am hard on the throttle. I don't know about a bypass either as I don't have one of those...but so far this pump has been reliable and is still working...it has roughly 60,000miles on it. I do have a back up to swap out just in case. It is the same p4601HP pump too.

A note on pressure...the most important thing is that it does not drop too much when you are on the throttle. In other words...if you have restrictions in your fuel lines the pressure will drop. If your lines flow well the pressure will stay around 12psi because the flow (volume) can keep up with demand. The big line kit you mention will go a long way toward improving flow. You will find that the LP/big line set up will help a lot. Adding extra pumps and cranking the PSI doesn't really solve the flow problem it just puts more pressure at the check valve in the VP44.

Good luck!

PaulDaisy

The advantage of having one is to allow your pump (carter being for some reason considered here as if it is different from other pumps) to discharge extra fuel when the demand from the VP44 is low, and the lift pump develops excessive pressure. Everyone agrees that Walbros, FASS and other high performance ones need a bypass to the tank. And yet, everyone just slaps in the Carter and lets it run against the dead end. How can one blame Carter pumps for lack of longevity when they are strained every time you turn the key or idle the engine? Yes, they are small compared to FASS-150 but they also build decent pressure, enough to damage themselves. If you let them bypass extra fuel, I bet you will put an end to the annoying LP failures.
-P

Hillcountry

Yeah, that makes a lot of sense. Thanks for the good info!
-Geoff

bnold

I've been running two campaign pumps down by the tank for around 35,000 miles now... The VP44 has an internal regulator at around 14psi that returns to the tank...

btroup69

You guys think its a good idea to add a filter before the lp. I would think that has alot to do with all the pump failure too because its gotta pump anything that comes out of the tank. Or does that create to much restriction and drop pressure too low?

Ph4tty

I used a carter pump on the frame with a big line kit and saw 15+ at idle and 12 at WOT. I wouldn't consider a bypass with that setup- I wouldn't want any less fp.

My current pump is simular to what the 12v trucks use and at 50 at cruise I decided to try a regulator. Simflow regulator, hoses, and fittings were less than $80 shipped from vulcanperformance. The regulator is snugged as tight as it will go and I get 18 idle and 20-22 at cruise =P

HOHN

I wouldn't feel a need to regulate FP that was only 15 dipping down to 12.

The purpose of a regulator imo isn't so much to protect the VP--- it's to give the fuel somewhere to go when the LP tries to pump fuel that the VP isn't willing to take. The VP does have the bypass at 14psi, but I suspect that it's not capable of flowing very much. After all, FP never seems to pause on its way up or down passing through 14psi. If it DID flow a lot, then the FP on the way down should pause at 14psi and again on the way back up.

Because I can't see any "bypass" action on my FP guage, I effectively consider the VP to be without one. Hence, I suspect at 15psi on the guage, that's about the extent of the pressure the stock LP can generate, not because of any bypassing action of the VP.

btroup69

Alright, sounds good. I'll just let it go and see what happens. Thanks for all the replies!!!!