Hi

I have a S5 13B Turbo. Im running a Walbro 255lph in line pump wired in with 12 gauge wire on a toggle switch..



At idle I run around 50 PSI of fuel pressure when I give it so gas in first gear the fuel pressure drops all the way down to 17PSI sometimes...???? It just started doing it.. so I take it that it is not normal..?? The engine is not leaning out but I'm still breaking the engine in so I dont bring it above 4000 RPM...



What kind of fuel pressure should my car be running at??? Do you think I need a new fuel pressure regulator??? If so do I need a new fuel rail to use a aftermarket regulator????



Thanks for any help guys...!!!

 

The fuel rail pressure will drop as you punch it, since the injectors are dumping the fuel pressure into the ports.



The pump has to compensate for the loss but it won't immediately. Not sure if it should be dropping that low, but you'll definitely see rail pressure loss when you go from virtually no injector pulsewidth to a ton of pulsewidth.

 

i'd set my base fuel presure at around 38-40psi (at 0psi boost, no vaccuum, you cna achieve this by pulling the vac line off the FPR while the car is running and setting it) and then work from there as needed.



What FPR do you run? What gauge are you using mechanical? digital? where is your pressure reading coming from, on the rail before or after the rail?



also what size injectors are you running? fuel filter new or old?



kevin.

 

I have a new stock fuel filter. The gauge sender is right after the filter before the fuel rail. I am also using the stock FPR. I feel stupid, But I was checking out all the wiring and vacuum lines ans stuff and The wire going to the sender was on there pretty good, but after I reinstalled it the reading got a whole lot better. Now I have 60PSI at idle and when I punch it it never drops below 45PSI now!!!



I guess the wire was not making a good enough connection.....



This is the first time I have had a fuel injected engine, And I have too much $$$ invested into the engine so I am a little sketchy...



Thanks for the input guys!!!!!

 

well I had good fuel pressure for a few days. Then it droped to 20 psi and leaning out real bad... So I replaced the pump and stil it only has 20 psi. So my next guess is the 18 year old FPR, but the FPR is built into the fuel rail.. So how should I run a aftermarket FPR??? Do I néed a after market fuel rail??

 

You could ditch the FPR on the rail, tap it to take a pipe fitting, and install a hose-barb end.



Then you could just run the aftermarket FPR inline to the tank return.

 

zipped off the stock one theres a bunch of crap inside cut some more... and theres even more crap inside.... The fuel rail's metal is to thin to tap...



Will a S4 fuel rail work on a S5 intake manifold... that could solve my problem..???



Humm... could I run A fuel pressure regulator after the stock one..??? especially If the stock Fuel pressure regulator is only making 20 PSI...????



where is a good place to check out a performance fuel rail...????

 

It's not too small you just can't tap it too deep. That or step your fitting size down, if you gotta have a ton of thread meat.





A pipe-thread style tap isn't designed to be bottomed out in any certain application. Only as much as you need, and then of course you would use a thread sealant when you spin the fitting in. Never over-torque pipe thread, you'll crack your part (not just fuel rails, anything).







You may also want to use a "Boss O-Ring" style fitting. Any local hydraulic repair or fitting shop can help you get the right sized fitting and a tap for going with boss instead.





Matter of fact, you could bring a factory fuel rail itself to a hydraulic shop, and they will do it for you for less than an aftermarket rail will cost. You just have to say "I have this here and I want a barbed fitting instead. What do I do?" Those guys are usually excited to do something that is related to fluid-pressure that isn't in the construction field. Some guys will do it for the cost of the fitting with no labour if you are charismatic enough. Remember - they get **** done that runs over 3000 psi of pressure, so the little stuff is fun for them.



Look up hydraulics in the phone book and check out the closest place. You're basically walking into a solution store for your situation, chances are they won't let you leave without having something done. They might scheme a way to get your new FPR mounted right on the rail. Who knows, check it out. Custom parts baby!

 

OK I drilled and grinded out the end of the fuel rail, and got ALL of the factory fuel pressure regulator out of the rail. Then I took a scrap of metal and welded a cap on the end of the rail.

I think this will do the trick....



So now that I'm going to be running a after market Fuel pressure regulator, I need to remove the Fuel pressure regulator control solenoid Right..??????



Thanks for the help guys!!