fuel pressure gauge is in

[swankmetal]

just got a 15 psi fp gauge in tonight. pretty cool to watch that thing move. highest i've seen is 16, lowest 3. idles about 13. 5. cruises about 14. wide open with about 40-45 psi boost it's at 6. it jumps up to 16 when i shift. i saw 3 once in 3rd when the back tires were going reeeeeeally fast (it was raining). so, is this about right for the piston pump? i remember reading something about 12-13 psi being max for the inlet pressure of the ve? am i remembering wrong, or am i remembering something that's wrong? man, these things (ctd) sure are FUN!



dave

 

[bgilbert]

You have two high flow banjo bolts yes? You have the sensor or tapped bolt for FP after fuel filter= the one to the left or nearest radiator= yes? Now is this with the 14mm head pump? 3psi is low, especially for the piston pump. I've never seen below 6psi, 38psi for however long I wanna watch the pyro rise. What FP gauge you using? I have a stock banjo bolt in prefilter side, so I could gain at least one psi wot there. How old is your fuel filter? And yes, your idle, cruise and 16psi sound ok for the piston LP. I think it can depend on restriction in ones fuel tank, fuel lines to the LP, and banjo bolts at filter and obviously the filter, oh and the gauge itself. GL says he's not seen less than 11psi or so wot. He's using a Westach electric FPG. When my mechanical FPG worked I never seen lower than 6psi wot. C'mon we need more info.

 

[Greenleaf]

I have not "SEEN" it drop past 11/10 psi at WOT that does not mean it won't. I have many other gauges to keep an eye on as well as the speed-o and the road ahead which often times is running a tad short. Bill is correct in that 3 is too low and the flow is directly related to your restriction, which is variable per vehicle. 6psi sounds the norm at WOT and 13/14 at average road speeds. Fuel temerature is also a variable too, don't forget. You guys DO have the dry ice contraption to circulate the fuel through... ... ... . RIGHT!!!???



Scott

 

[swankmetal]

yes, genos tapped bolt after the filter and my drilled stocker before. the 3 psi was only when the back tires broke loose. other than that, i couldn't get it below 6. the gauge i'm using is from surplus center. an autometer industrial mechanical gauge that cost me a whole $9 new. now scott, is this another one of your "experimental" projects? oh yeah, this is all without the 14mm stuff. hopefully in the next few weeks i'll be able to afford to have that done though. i wanted to be sure i was able to get some good psi #'s before i did the switch. if pressure drops too much, with that amount of flow will i be able to use a 2nd gen lift pump? or will it still be too much inlet pressure? i'm sure we'll find out.

 

[Greenleaf]

Dave,



I have not done this yet, however other piston lift pumps will bolt right in. The fuel line fitting will have to be changed as the 2nd gen pumps use a set of inlet/outlet fitting that are twice the size. You will then be limited in the amount of fuel the pump can suck through the little supply hose.



My buses use the same lift pump and they are equipped with a 1/2" supply line to the lift pump from the tank. This is how I aquired the idea of a piston pump. I knew that the pressure would be too much though. They operate about 18 to 25 psi. The spring is removable so one could adjust said pressure with modifying the spring I suppose (????)



Scott

 

[bgilbert]

They operate about 18 to 25 psi. The spring is removable so one could adjust said pressure with modifying the spring I suppose (????)

But you don't want that much pressure going to the VE pump. IMO not a worthwhile investment unless you could get the 2nd gen piston LP off a donor or core motor cheap, then do some R&D on it. I think we need to see how far 6psi at wot will take us. I know guys with stock LP's have hit 400hp?? Which 6psi is about tops for the stock LP, let alone at wot. Stomp and KTA both run something different than a stock LP nor a piston. I believe they both run some form of an electrical LP. Some have said you don't wanna see higher than 15psi to the VE. Good thread about this on 'KTA's site'.

 

[swankmetal]

can you explain this one??? i changed the wif sensor today (but not the filter) and am now seeing 15 psi at idle and 15. 25 psi at cruise. when i first started er up and for about 10-15 minutes of driving afterward, the needle didn't bounce like before either. whadya think?

 

[bgilbert]

Well first off the bouncing needle is not a good thing. It will lead to the death of your FP gauge. With the replacement of the wif sensor you may have gotten rid of some water, some of the dirt from the old filter which is less restriction now ya seeing 15psi at idle as compared to 13. 5 before. Wouldn't worry about it. 13. 5 or 15 at idle no matter. Its the WOT number that is important. This LP is designed to push so much, so seeing much more than say 16psi probly won't happen. Its designed for use with a VE pump, so on paper it shouldn't produce enough pressure to harm the MIGHTY VE. I see different pressures under various conditions. Cold, warm, hot, fuel, filter restriction etc. Get that pump gone through and new rotor head installed and get er on a dyno and lets see what the piston LP is capable of!!

 

[swankmetal]

will do!!!!

 

[swankmetal]

well, it's a fact. i saw 3 psi just after the shift into third today, with OUT the tires spinning. does this mean i need to replace the whole tank/line set-up?

 

[Greenleaf]

If your the only one that has seen 3 psi with a modified VE and a piston lift I'd do the following.....



Question if the gauge is true. If it's been bouncing it wrecks the innards. Second, I'd suspect the fuel filter. Third, I'd suspect a fuel restriction in line and or tank pick-up. Most likely the restriction is in the pick-up screen from what I have heard.



If you get the tank down you might just as well rig/fabricate a larger pick-up tube and pull them fuel lines out. If you see the screen covered with trash, you'll have solved the majority of the problem.



Other than that, I'm out of ideas. At this time.



GL

 

[bgilbert]

You got me. I just don't see how the piston LP can bog down so far even if you lugged the hell of it into third, say starting in 3rd gear!!?? You are using Cummins 3936320 LP yes? I guess if you're worried about it, time to sell the piston LP to a less than 400hp guy and invest in an electric LP of some sort. KTA is using something he said gives him about 15psi wot,... i could be wrong. . its in a thread I started on his site. ..... but hey if its not stalling, dieing, whatever, run with it, get it on a dyno, find out if mr. piston lift pump will be your limiting factor. If it is, I'm sure it will look good on the mantel or computer desk, they sure are SEXY!! :-laf

 

[swankmetal]

thanks guys. i'll add that to the list.

 

[PToombs]

My wife isn't thrilled with my truck, but she thinks my tractor's sexy!!

I guess you can't win 'em all!