NJTman

So today, I spent 2 hours or so putting in my new Fuel Pump and filter.

wasn't as difficult as I thought it was going to be, so all worked out fine.


Since my normal FP pressure was in the 3-5 psi range, and it fluctuated quite a bit between those numbers, I was a bit surprised to see the new FP's pressure, and it's consistency in being so.

The new FP has a 6 PSI average pressure most of the time (which I NEVER saw on the old pump) It fluctuates a little bit when driving around, up to 7 and back down to 5 on a rare occasion, but for the most part it stays at 6 PSI unless I whomp on it.

In the name of testing, I took the truck out to the highway and stomped on the throttle. It developed 24 PSI of boost, 1100 degrees EGT, and the fuel pressure dropped to 3 PSI at WOT. Not sure why ? Is the FP supposed to be dropping during heavy acceleration ? Once I took my foot and resumed normal driving posture, it returned right back to 6 PSI and pretty much stayed there. At least now, I'm not getting 0 to 1 PSI at WOT.

Tomorrow I'll play around with the KSB and see if it's doing anything it shouldn't be. After that, the next chance I get, I'm heading back to that hill to see if it's any different.


Funny.... 24 years and 200,000 miles and the pump lever still worked, and it still produced 4-5 PSI before I took it off. I bet it wasn't made in China....

bigragu

The fuel pressure, the way it's supposed to be read, is not like how we read boost. Boost build up, turning the needle clockwise on our gage as we romp on it. FP is the opposite. At idle at a stop you will be seeing the pressure of say 7 psi on your gage and the minute you punch the throttle the needle goes counter clockwise. I believe 3 psi on the OEM gage is what you do not want to go any lower than. If you are seeing more readings later on fluctuating around 3 psi to 2, your filter is building up crud. FP gauge is a great tool in determining the change of a filter.
When you can one day, invest in a plunger type lift pump, TMan. You will just be in heaven with those fuel pressure readings. With a clean filter, my pressure readings hover at idle around 16 psi. At wide open throttle, clean filter, I pull it down to around 11 or 12 psi. If it goes down to around 9psi it's time to change the filter.

KRB

I all of the sudden had trouble climbing a hill (pre fuel gauge) and replaced the lift pump with a napa unit. Now i have 7-9 psi at cruise, not noticed what it reads at wot. Seems high for idle though?

NJTman

I'm consistently at 6psi, unless I'm whomping on it, then it drops to 3psi. Not really sure if having greater fuel pressure for just normal driving is a good thing or not. I think I'd be worried about leaks if too much pressure was being brought to the IP.

j_martin

The VE pump has a transfer pump built in. Theoretically it can function as a lift pump, as it does in some applications, like a VW 4 banger. All it does is fill the chamber of the injection stage, which delivers it to the injectors at 3500 psi or so.

As long as fuel is delivered to the VE at adequate volume to satisfy the demand, you can't increase performance by increasing the pressure. All you can do is risk damage to seals. If you have a few lbs. of fuel pressure during any demand, it's adequate.

KRB

So did you try it on that hill yet to verify it was the lift pump?

Drove mine yesterday and watched the fuel PSI. It ranged from 6-9. Roads too wet to build much boost so the most I ever achieved was 17psi boost and the fuel dropped to only 6psi. Maybe my gauge is off now...

NJTman

Not yet. I may go today.

It's 30 miles from home, and heading towards traffic, so I have to find the right time. I'll be sure to post what I experience when I do. It would be nice to test it, do some IP tinkering (smoke screw, boost adjustment, spin the fuel pin) to see what happens, but I'll wait till I make a pass and then do that stuff.