cummnz4x4pwr

Fuel pressure that is.

Ok here's what i did last night......

Before I had 25psi @ idle and 40psi@ 2000rpms with just a stretched spring and I could drop it to 8psi on a WOT run.

Well I had a spare overflow valve so I stretched the spring then I got a spring out of a ball point pin and clipped it to the same length as the strecthed spring. well the results are great Ive got 45psi @ idle and 60psi@ 2000 rpms(free rev) and cant drop it below 35psi.....I LOVE IT!!!!!!!!


Jake

gman07

Should be an inexpensive mod Sounds like the results are pretty good too.

How much pressure is too much for the P7100?

Mopar1973man

Geez at first read I was thinking that's way too much for a VP44!!!

But for a P-pump that's about normal...I'm not sure of the high range of pressure is...

cummnz4x4pwr

25@ idle is normal for the p-pump

jake

TxDiesel007

Might not always be a good thing

i think thats too high, cant it damage any of the internals? I have a super slow responding gauge, and i see at idle about 20 psi, and 30 psi on most occasions running around town, and have seen mine as low as zero in WOT runs...

How does ur gauge respond? is it almost instant or it takes a good while like mine, i have my needle valve closed almost completely due to it reading at 10 psi at idle and 20 max when it more open before..

Perhaps ill try that overflow valve trick, dumb question, does the top part come off of it? sorry i had to ask, i aint messed with one yet.. but i do have my old one.. lemme guess u have two springs in ur overflow valve? im confused.....

Rick

cummnz4x4pwr

actually it will not hurt anyof the internals... patty haisley told me that they would rather see them @ 60 @idle then anything else. and yes the top comes off.... you just stretch the original spring then get a ballpoint pen take the spring out and clip it to where when its in the bigger spring they still compress fully then reassemble.

Jake

Rick[/QUOTE]

TxDiesel007

I have got to hand it to you Jake

I dont know how u discovered this, But it works like a charm... My fuel pressure was at 10 psi at idle, yes u read right, so i took my stock overflow valve that came with the truck and took it apart and did as you said..

I experimented and simply stretched the spring a couple of milimeters, and then i clipped the spring about the same legnth as the spring that i removed (stock spring and assembly was already inside when i put in the ball point pen spring) and put it back together, tightened the top of the OFV (14mm by the way) to 25 ft lbs, and placed it back in the truck,

Started up the truck, 40 psi at idle! YES!!!! and 55 psi at 2500 no load, and i cannot drop the FP below 30 psi at WOT...

I feel like i have gotten some power back, BUT the question is how long will this mod last... i have a feeling it will eventually lose some PSI due to spring wear, but for the most part, im gonna ride it out for now..

Thanks for posting!

Rick

12valve

when im only stretching the stock spring, the lp pump starts ticking! Is my lp bad?

idle 37 psi
cruising 35 psi
WOT 0 psi

LanceD

how far do you stretch the original spring? also do you cut the pen spring to the same length as the spring when its stretched? what kind of pen did you use???

12valve

i stretch it a lot, and it goes back together, and let it 1/4" to 1/2" longer

you know that best by hooking up a fp gauge with a needl valve!

just by taking it apart, be carefull, theres a little cap in there, a ball, a spring and maybe a washer or so.

TxDiesel007

I stretched my original spring

when it was already inside the valve body, i placed the pen spring in there, and clipped it to the exact legnth of the stock OFV spring, i then capped off the OFV and turned on the truck...

what kinda pen? If i remember correctly it was a papermate with the little grips on it...

Rick

TxDiesel007

My LP doesnt tick

so it could be a bad LP, not so sure. Does your pressure vary too much from those numbers?

I know i idle at 36-40 (depending on time of day and temperature, no explanation on that one), and i cruise at times from 36-42 psi, At WOT i drop down no more than 15 psi from where i was, so i see as low as 22-25 or so at WOT..

I have narrowed down fuel pressure to fluctuate and its only natural, to four factors IMHO

Fuel viscosity
Temperature
Idle setting
Time of day

my truck will idle at times at 750 and FP is right at 36-38 psi, when it idles at 900-1000 (my governer sticks i guess) the FP is right at 40 psi. I have also found that in the day time my pressure is a bit higher than at night time as well, no explanation for that either, time of day, well directly coordinated to temperature i would assume, and fuel viscosity, well its beyond any of our controls...

As i have learned from Bill (Infidel) FP, is nothing but an average, and its not out of the norm for averages to occasionally fluctuate, ive pretty much learned to accept my FP and as long as it dont drop to ANYTHING LESS than 30 psi at all at idle, ill go ahead and live with the minor inconsistencies..


Rick

12valve

i dont really care what it shows at idle.

i need 20+ at 3000 rpm and over! the inj pump sucks the last drop of fuel out of the guage, and the need pings to cero

Crimedog

12valve,
I've read many times on here that a ticking lift pump is the sign of a dying one. Sounds like yours is on it's last leg.

Jambbii

I stretched mine to 40psi at idle and at WOT its 0 still with a brand new lift pump. A new fuel system is being assembled as we speak.