I hope someone can help guide me in the right direction. My car is an EVO4 (track car only) and has had a relay fitted to the fuel pump to bypass the 2 stage pump. I fitted a Walbro 255 pump and that's where my problems started. I measured the fuel pressure on the return line and it's 40 PSI (way way too high). I have read about a mod to the 3 way bleed over junction inside the tank which should be drilled out (not sure on what size to drill it out to). are there aftermarket units available? If so whats the units name and where can I get one? The other question I have is there a filter inside the return line that may be blocked. A big thank in advance.

 

Well I have found out it's called a Jet Pump and you can get an aftermarket Sard unit but my first thought is to try drilling my original one out. Anybody done this and if so how big did you drill the hole?

 

why bypass the 2 stage when u already installed a bigger pump?

 

It was done before I bought the car on a std pump. I upgraded to a Walbo 255 and at the same time changed the wiring back to std. When I went to the track last week I had servers fuel starving and the pump was screaming like made when I pulled back into the pits. I thought the pickup was blocked so I took the pump out and cleaned the screen but to no avail. I have just drilled out the jet pump to 3.5mm and the fuel pressure on the return line came down to 12 psi car idles much nicer with a 13:1 air fuel ratio. A little rich I know but better than it was. Do you recommend wiring the pump back to std for track use?

 

Hmm looks like little knowledge in this area. I am surprised.