Engine/Transmission (1998.5 - 2002) L/P and the bottleneck finish filter

[RADdodge]

FYI...

BTW, it's a 2 micron filter before the injectors (factory is 45gph/2 micorn). I use a 30 micon before the pump(s).

 

[Whitmore]

Tonight is my last night shift and I will have 7 days off so I will jump back into the middle of this thing and see what I can find out, I plan on taking the filter housing off and disect it , I have an idea since I am plumbed with hose now and that is to come off the discharge of the pump to a seperate hose and with the filter and housing in hand and a short hose so I can shoot it back into the tank or even a bucket so I can measure the GPM, I will let you know how it turns out.



RADdodge, please e-mail me info on these filters to -- email address removed --



cheers, Kevin

 

[15w40]

#ad


In physics, the concept that as the speed of a moving fluid (liquid or gas) increases, the pressure within that fluid decreases. Originally formulated in 1738 by the Swiss mathematician and physicist Daniel Bernoulli, this principle states that the total energy in a steadily flowing fluid system is a constant along the flow path. An increase in the fluid's speed must therefore be matched by a decrease in its pressure.



Bernoulliís Principal - as the velocity of a fluid increases, the pressure exerted by the fluid decreases

Venturi effect - reduction in pressure of a fluid resulting from the speed increase as fluids are forced to flow faster through narrow spaces

I believe that the pressure at the filter end of the AN fitting is the same as the pressure at the VP-44 end. I have exaggerated the necking down of the AN fitting to illustrate the point, but even with no reduction in cross section the pressure to the gauge will drop at high flow rates. But then again, I could be a complete lunatic.

 

[tractorface]

The question im my mind is this



Is the actual pressure important or do we just want to make sure the VP-44 feed line is full of fuel and no air. I would think the VP-44 would be happy drawing fuel from a bucket right by the inlet. I kinda think we use pressure because it is easy to measure and gives us an idea of how the system is working. Read an earlier post by some fuel pump engineer type that said the VP really wants a steady stream of fuel with as little turbulance as possible. I am just asking because my future plans call for an increased demand for fuel and I want to get it right. I suspect some of the current solutions are just band aids.



So my question is what does the VP-44 ideally want for fuel supply? Can't imagine that pressure is as important as volume.



I am definetly no expert just someone with questions

Thanks

 

[RADdodge]

Many, many discussions about that, and you are right, volume or flow is the key. However, flow meters are much more expensive than pressure gages and the gages give a general idea of what's going on. If there is a 0 to positive pressure, the VP44 is getting what it needs, if the pressure is negative, it's not. It's about that simple. However most here use the pressure gage to determine if the lift pump is working like it should. Anyway, this problem has my attention! Dave has a good point about venturi effect and why the pressure may be reading low (zero though?). Time will tell.

 

[fest3er]

Re: OK hears the deal Guys

Originally posted by Whitmore
... Hear is where I am confussed, my numbers soud better than any I have read hear for the stock l/p but what is up with the damn thing dropping to 0 psi at 100mph :confused ...

What is the likelihood that the fuel pump is going into 'bypass' mode? I've been seening all along that the post-LP pressure drops to zero. But if the lift pump stopped moving fuel completely, shouldn't the pressure be *negative*, as the VP44 is trying to suck fuel throught he LP?

I'm wondering if the LP is going into by-pass mode, but still supplying the fuel the VP wants. And it would seem the bypass valve is a little too weak; try putting a more durable spring in there.

Fest3er

 

[RADdodge]

Originally posted by Whitmore

... BUT heres the deal while the VP reads 0 and I switch to read the psi before the filter it will read 11-12 psi, so I now know that the l/p is still supplying pressure to the filter but the filter cannot flow enough to the VP...



cheers, Kevin

I would agree except he sees adequate pressure before the OEM filter while the pressure on the other side goes to 0. Good point to keep in mind though.

 

[15w40]

I’ll bet that if Whitmore takes the hose off of the VP-44 and sticks it into a bucket and then bumps the starter, the fuel pressure (pre-filter) will be much less than 11 psi. This will indicate the pressure when running at full speed is not zero.

 

[Whitmore]

OK boys and girls

Here's the deal, I had time to go thru the system with a fine tooth comb, I tore it apart from A to Z, looked the filter system over very carefully and came up with no valid reason for a DP, all hoses looked fine and all -6an fittings were good as well, OEM fresh pump is working very strong and delivering plenty of fuel as I shot some in a bucket (6 psi), spillback or return fuel from the VP-44 and the head gallery is returning the cooling and lubricating fuel into a bucket well too. I made one change when I went back together with it all, I moved my psi sender from the inlet of the VP to the discharge of the OEM finish filter and guess what ... ... ... ... ... ... ... ... ... vvvvvvvvvvvwolla Problem gone, Now upon testing with comp on 5x5 at WOT I see 11 psi prefilter and 10 psi at post filter so this leads me to believe that 15w40 is absoluty correct in his theroy of the sender getting some kind of a ventury effect, its the only rashonal thing I can come up with at this time

I am happy with my fuel delivery system and think that the head psi from the aux tank as a main feed is going to increase the life of my OEM L/P and the drive motor as well... ... ... ... Thanks to all who pushed me along with ideas and a sharp stick to get it right



cheers, Kevin

 

[Big White Beast]

WooHoo!!!!!

Always good to solve an unusual problem. It must be the type of fitting used to tee for the sender. Many people have one on that point, near the VP, with no apparent problems.



Good news is you were never starving the VP for fuel so no future problems should come from that. The only question now would be how long the OE lift pump will last in that location.



Garrett