ThreeHonks

iTrader: (10)

quick question:

Is it possible for the stock FPR to fail and there be NO trace of fuel or even fuel smell coming from the vacuum line?

RamAir95TA

iTrader: (2)

Sure.

ThreeHonks

iTrader: (10)

OK. I just want to do some tests with my fuel system to make sure it has stable fuel pressure before I go and take it in for a tune (speed density)

What is the best sure-fire way to test it then? Will hooking up a pressure gauge suffice?

RamAir95TA

iTrader: (2)

The real way to diagnose the FPR is with a vacuum pump. With the pump running (jumped via the 12v+ prime connector on the passenger side of the engine bay) and applying vacuum to the line you should see the fuel pressure rise.

ThreeHonks

iTrader: (10)

well my main concern is that it is letting too much pressure go by. My plugs are a little darker than they possibly should (lots of idle time tho).

Everything may be working just fine and its just how the open loop/SD tune is. Yep, im in race car denial

ThreeHonks

iTrader: (10)

anyone? Will testing the pressure at the shrader valve tell me if I have a failing regulator?

gregrob

iTrader: (8)

I would hook a gauge to it and see what your pressures are. What pump?

ThreeHonks

iTrader: (10)

Just a walbro 255. I just rented the tester today...


So the plan is: Going to check fuel pressure at idle and pull the vacuum line off. If I see any crazy high pressure (like 50lbs) then I know something is up and I will replace the reg. If its around 45 I will leave it be

Phstratton

iTrader: (1)

How did this turn out?

ThreeHonks

iTrader: (10)

havent been able to do anything with the car. Living in Michigan makes it too cold to even open up the garage. I will try to test pressure next week (suppossed to get warmer)

I'll let you guys know my idle fuel pressure and then the pressure it goes to when I take the vacuum line off.

ThreeHonks

iTrader: (10)

so I got around to testing this today.

At idle I had about 46-48 psi and then once I took the vacuum line off it went to 50 psi or just a tad over. Once I turn the car off the pressure is immediately gone. Nothing is being held in the line it seems. When I touch the throttle off idle (less than 3000 rpm) it seems to bounce around a bit, even dropped to below 40 psi for a split second... I have a Walbro 255, so fuel is not an issue, especially at only less than 3000 rpm

You guys think its safe to say my FPR is failed or in the process of failing?

flame

iTrader: (13)

They rarely go bad. If the test gauge is cheap and has been dropped a few times it could be out a few psi. The pressure dropping almost instantly when turned off is more of an issue. Leaking injector or bad pump check valve.

ThreeHonks

iTrader: (10)

The gauge is brand new. First time it was ever used.

-I dont think I have a leaking injector, because mine were all flow matched and tested recently. But thanks for your input, I think I am going to check them for leaks anyway

-I hear some pumps dont have an internal check valve. What is it even there for?


I ended up ordering a stock new FPR and im gonna put it on today. There is really no way of knowing whether it did anything or not, but I guess its peace-of-mind if anything

My very reputable tuner did say that if a FPR is failing, then it will cause the rear cylinders to run a tad rich, and my richest plug is #7, followed by #8 in a close second.


Anymore input on this? I already pulled the fuel rails apart so it looks like im going to replace the FPR either way.

flame

iTrader: (13)

All in tank pumps have a check valve to keep the rails full otherwise you have extended cranking at start up

Wicked94Z

iTrader: (26)

i have a good used one off my motor, gimme 15 shipped and it'll be on it's way this afternoon

ThreeHonks

iTrader: (10)

just bought one thanks for the offer though

ThreeHonks

iTrader: (10)

well guys, as you know I put a new regulator on and finally started it.

I am very happy with what I found. Idle is at a steady 42-44ish psi, compared to the 50psi I had.

If I keep the vacuum line on and give it revs, it will drop down a bit and get jumpy and somtimes go down to 30psi for a split second. But if I have the line off, and give it a rev it will hold steady at constant pressure all the way through the rpm range.

WTF

I capped the vacuum line off entire and capped the regulator and it held steady through the entire RPM range. Did not flinch one bit. Should I just keep a vacuum cap on it? Isnt a constant/reliable/steady pressure what you want?

flame

iTrader: (13)

Put the gauge up under the wiper arm where you can see it and go do a WOT run. If it drops below 39psi you have a supply problem plugged filter, weak pump. It takes pressure and volume. Just because the pump has pressure at idle and free rev doesn't mean it can supply the volume of fuel to maintain the pressure under WOT.

ThreeHonks

iTrader: (10)

My fuel system is adequate for what I am running. I have done that before.

I need to know if its good or normal for it to get all goofy and drop off when I rev it with the vacuum line ON?

ThreeHonks

iTrader: (10)

anyone have any input?