Just wondering if anyone has any ideas as to why my fuel pressure won't hold at Full throttle on my VLT I'm running base fuel pressure of 42psi. Turbo is running 14psi. With my 1:1 fuel pressure reg, fuel pressure should be approx 56psi at 14psi It only hits 56psi for a second, than drops straight down 42psi. Why is it doing this ???????? Fuel system consists of: Peirburg hi flow lift pump Bosch 044 external pump GTR 444cc injectors Aeromotive 1:1 rising rate regulator Brand new Ryco Fuel filter All above parts are 2 weeks old except the 044 which is 10months old

how are the pumps powered? i found out the other day my 984 in the boot is only seeing 10v, which will be the cause of my leaning out in the topend. atm the 984 is running on the stock loom. anything bigger then stock will need a relay and bigger cabling

Yep, i upgraded the wiring to thicker grade (25amp) plus added an addition relay few months ago I've tried 3 different fuel regs and they all do the same thing, so i can rule out the reg 100% Do the factory fuel lines need to be upgraded to bigger size?

I know you have changed regs but...... It seems very coincidental that the fuel pressure does not just drop off , but falls exactly to the base pressure set by the reg ? Where are you taking the vacuum/boost feed for the reg from ? You have a lift pump and a external high pressure pump so assume you will be using a surge tank, can you rule out fuel supply from surge to the 044 ? Is your main fuel tank breathing OK ? (not creating a vacuum slowing fuel supply) Fuel filter not blocked ? MT

how are you setting up the fuel pressure gauge?>\

Quote: Originally Posted by mumstaxi I know you have changed regs but...... It seems very coincidental that the fuel pressure does not just drop off , but falls exactly to the base pressure set by the reg ? Where are you taking the vacuum/boost feed for the reg from ? You have a lift pump and a external high pressure pump so assume you will be using a surge tank, can you rule out fuel supply from surge to the 044 ? Is your main fuel tank breathing OK ? (not creating a vacuum slowing fuel supply) Fuel filter not blocked ? MT I'm taking vacuum/boost feed straight off the factory intake manifold, running about 60mm of vac hose, boost is taken from a t-peice in this hose too and its reading fine on the boost gauge and ecu I'm not running a surge tank. Fuel filter is new, fuel pressure was doing same thing with old filter too In regards to fuel tank breathing? All breather lines look ok visually Quote: Originally Posted by airbagsVL how are you setting up the fuel pressure gauge?>\ The gauge is attached to the reg

does the car feel like its starving for fuel? im inclined to think your pressure is fine however its something to do with the way your gauge is setup, as said above its too much of a co-incidence that the pressure drops back to base pressure everytime... Also a 1:1 regulator is NOT rising rate as you have said above

Car was on dyno and AFR's were going mega lean at the same time fuel pressure was droping, don't think its the gauge We tried 3 different fuel regs on the dyno, when the pressure dropped it didn't go to exactly 42psi (base pressure), it hovered around 38-42psi etc Might change my 044, even tough its only 10 months old, it makes some strange noises sometimes..

Intank pump OK? Pickup not blocked? See what the low pressure pump flows per minute, if it's not picking up fuel properly you will have trouble keeping the pressure up.

I fitted a new intank pump 2 weeks ago, i primed the intake pump for about 4sec with the hose disconnected and it covered most of garage floor in fuel Lol, The pressure was so good that it knocked the jerry can over

id try fitting a surge tank beroe anything else. that'll gaurantee youre pump is getting the fuel it needs

i had fuel line problems and thus fitted big -8 lines and that fixed all of my problems. mine was a n/a so i only had 5/16 lines , just a quick question what size are the turbo fuel lines?

rodger1: I've been thinking about the lines ever since i came across this problem. They look like the factory 5/16 lines which are tiny I was going to upgrade the lines but I know a few VLT's with around 250-280rwkw and they all run factory lines which is so confusing lol

hey just thought of a test you could do, with a fuel pressure gauge on the dyno when the pressure starts dropping off clamp the return line if pressure goes up it is defiantly reg problem if it stays the same it's a supply problem