Pitt

Ok, I got a supercharger and upgraded to 42lb injectors, lmaf and a walbro 255lph fuel pump. I got the car Dyno tuned by a very reputable company here in FL. at WOT car runs great, did 370hp at the dyno. My concern is that when Im about to start my car, I turn on ignition and before starting the engine I notice on my fuel pressure gauge that the PSI needle is all the way past 100 psi . When I start the car, it starts fine and fuel pressure drops to like about 25psi at idle. When Im driving just cruising, fuel pressure is about 25, 30 or so....needle jumps up and down constantly. If I accelerate just a little bit, the fuel pressure will rise up to past 100 psi again and as soon as I let off the gas it drops back down to like 25(needle always jumping). Could it be the gauge? Or just the walbro pump, Ive heard they act weird since they werent made for returnless fuel systems. Any suggestions welcomed and thanks.

97targa

Sounds like your getting false readings. Your regulator doesn't let that much past. This is gonna sound funny, but check your PCV valve make sure it's good. It can cause positive pressure out of your injectors which will give you those readings!

Pitt

Hmm, well I had my PCV valve disconnected from the Throttle body vacume for a couple of days but I now removed the PCV valve and have a Breather can instead, both valve covers just breath into breather can without vacume assistance.

ktm300

Could that just be your gauge getting power and turning on? If you are concerned about press you should put a mechanical guage on the fuel rail and have someone start the car while you watch it.

Pitt

Well if it only did it at start up I wouldnt be too concerned and think its the gauge but it does it while im driving normally and if I WOT it goes all the way past 100psi. Im gona stick a manual gauge on there tomorrow and rule out if its the gauge/sensor or not.

ohthreeGT

the 25 lbs when running sounds too low as well, its prolly a bad guage/sending unit

2000GT4.6

His car doesn't have a regulator at all. The 99-04 GTs have a returnless fuel system.

My SVT pump runs about 45 PSI at idle and aroudn 60 PSI at WOT. 100 PSI seems like its way too much.

contentsunderpressur

It's a faulty gauge. If your pressure was that high when you turned the key on your injectors wouldn't fire.

contentsunderpressur

When your idleing and pulling vacume your pressure will be a little lower than when your giving it gas. If your n/a and give it gas your vacume goes away and equalls out to 0. Your pressure should be around 40 then. On a boosted car the pressure will be low at an idle, jump to around 40 or 45 when the vacume goes away and the boost gauge goes to 0 and for every lb of boost the pressure will rise 1 lb.

AmericanRicer87

It's an electronic gauge? make sure the signal wire to the gauge isn't grounding out. All it takes is a small cut in the wire or a connection touching somewehre. It can be the sending unit too.