I am on my third lift pump at 90000mi and I am going to install a Holley Blue as a pusher. Three questions. Should I bypass the stock lift pump? Is the Holley Blue strong enough to maintain adequate flow? My engine, at 215hp, is totally stock. I have seen some posts that say this pump is not strong enough by itself for their trucks. Last question is about wiring the pusher pump thru a relay. Since the ECM runs the lift pump at reduced voltage during cranking, will I not run into starting problems with the relay feeding full voltage to the pusher pump during cranking? The draw of the Holley, at 3.5A, is the same as the stock pump, so I could wire the pusher pump into the stock harness without overloading the ECM and still have reduced pressure during cranking.

 

I have my holley in line and wire to the stock pump so it all works together. Been workin great for 9k at 19 psi.

 

I mounted a Holley black on the frame as a stand alone pump. Picture is in my gallery. 13 lbs idle. 10-11 cruising on the highway. 9 is the lowest I could get it wide open or pulling. Works good but I've only been using it for about a month now.

 

Holiday and DieselRob. Do your Holleys pump at full voltage during cranking and if so would this not lead to hard starts?

 

FWIW - Prior to the FASS I had a carter pusher pump (running off of a relay so no reduced voltage) back at the tank in addition to the stock lift pump in the stock location and when it all worked saw about 20psi at idle. With the FASS (relay - no reduced voltage) I am currently seeing 20 psi at idle. I have never had a hard start issue.

 

I just extended the stock harness so it basically works the same as the stock lift pump. Been working fine so far.

 

At what voltage do the pumps run at start? Are they "unrestricted" during regular use - i.e. 13.8 v or whatever the system can provide?

 

Holiday. I just looked at the picture of your pump. Is the Fram oil filter pre- or post-pump?

 

It is before the pump. I just wanted a filter to take out the majority of any garbage before it hit the pump and main fuel filter but was inexpensive to change so I can change it often. That's why I picked that filter.

 

I replace the lift pump with a holley blue near the tank. I did the 'stretched' thing to the spring. At idle I have 14 PSI, cruising 14 PSI, hard hauling up hills 16 - 17 PSI, WOT 14 PSI. It never really changes much, just what the computer tells it what to do. It has been working fine for 30K miles. Ahh yes it is wired into the lift pump connector, no relay. My gauge is measureing at the injector pump, post filter.

 

HOdiesel, did you try the pump before stretching the relief valve spring? If so what was the pressure? I was wondering if maybe I should boost mine a bit and if that would do it.

 

What is this spring yall speak about??? You're saying you increased your FP by "stretching it"? Do I have one? sorry for the 1st grader questions.

 

I am currently unravelling or at least trying to unravel some myths and facts about pressure vs. volume.

I have learned that a pump that is rated at 160 gph at 12 volts is rated with zero pressure. No resistance.

That same pump moves 188 GPH at 14 volts...zero psi.
Have the pump working at 20 psi [more resistance] and its running at around 25 gph. The pump is working much harder too, correct?

So I need to get my head wrapped around this a bit more. Maybe someone can explain this to me.

If I have a pump that is providing 100 gph at 10 psi and drops to 60 gph at 5 psi at WOT on a truck with 500 HP , would that not be better then a pump that has a higher pressure?

I am going to try and lower the pressure on the pump I am testing down to 12 psi at idle and see how far it pulls down at WOT. I am beginning to think theres a line where pressure vs GPH can also work against us.

Scotty

 

I don't have any experience with the Holley pumps but I am pretty sure that your figures of 100gph @ 10psi and 60gph @ 5psi are wrong. Where did you get those figures from? Also once the pressure drops below the releif valve setting the valve has no more influence on the pressure. At WOT the releif valve setting would be immaterial unless you set the releif valve very low and there is no benefit to doing that.

 

I know they are wrong...it was hypothetical. I have a picture awaiting arppoval in my gallery that shows the numbers for the pump I am testing.

What is the ideal pressure vs volume for our trucks then? What would work best at idle, cruise and WOT? Which pump fits the demand of a truck that is stock, 300 rwhp, 350 rwhp and so on?

Scotty



admin edit to add approved graph
Ed