sluggo42

So my fuel pressure recently started getting real jumpy, so I figured the LP was bad so I changed it out with another stock carter. I have the Vulcan big line relocation kit so it was easy. This first pump has been fine for 5 years with my edge juice/ attitude. Always ~12-13 psi, down to 9-10 at WOT.
Just the other day i saw it was all over the place between 4 psi and 13 psi. So I changed it with my new spare and got 15 psi immediately! I thought I was good until 3 minutes later and the pressure started going nuts again.

I searched the site deeply and found numerous posts about the possible problems. Many people were quick to condemn the carter as junk and to proclaim their system as the Holy Grail, like FASS, Airdog, Holley ect...

Since I had two pumps immediately show the same symptoms, I started to gravitate to a voltage drop as a possible culprit.

I have decided to try bypassing the ECM for starters, to see if I can maintain a solid pressure. I came across this post, and wondered if anyone could explain it a little clearer for me, as to where to get my 12v power from exactly, and how I should ground it as well.
Here is the post :

If you decide to bypass the LP you should consider a setup like this:

Ignition switched + to an oil pressure switch that's closed with oil pressure there (and a bypass with a pushbutton) to a relay - this relay should power the LP.
The reason is that the VP44 hates high pressure while cranking and with the oil pressure switch you can eliminate the problem. The bypass pushbutton comes in very handy for fuel filter changes. (Wrench on the filter outlet plug and finger on the button makes for an almost dripless air bleeding )

HTH

AlpineRAM

Anyways, I also should mention that I found that a few people experienced shorts within the Vulcan Harness extension.
I'm not sure how to get inside of the factory sealed wire connections either.. Should I shave away some wire insulating plastic to get to the wire right behind the plugs to make connection points?

Thanks for the help in advance,


Doug

mini14

research relay wiring and you'll understand.......1st wire.12v comes from a lead directly off the batt. 2nd wire is the oil pressure switch is a trigger, and the 3rd wire would be 12v out of the relay, 4th wire is a ground

totalloser

Another option is to use a relay to take the load off the pcm.

But relocating the lp onto the frame is a really good idea. Basic parts store Carters (same pump but with npt fittings and regular wires) usually come with fittings and a rubber isolated frame mount and cost less than half as much.