Calling all fuel pressure/fueling experts! Mike2ptZero also!

[Ewok_Fetus]

I am sure a couple of you remember my post a week or so ago with the "low requested boost" and slow caps times... Here is a link to some info from Audizine... http://www.audizine.com/forum/showthread.php?t=222761 I was told to log a NUMBER of things which the only things out of place were the requested boost/actual boost and my AFR of 10.8:1. Well, I was instructed to look at my block 032 readings... Okay, -.2 and -4.2... The 2nd number actually fluctuated a bit... But it was the 1st number that grabbedd my attention. I read the Bently that it must be AT LEAST 2% in either direction... I followed all of their trouble shooting an still nothing... I just didn't check the fuel pressure... I got under the hood and looked at the FPR line and it was loose at the intake manifold... Replaced that line and made it air tight... Okay... Still logging the same stuff... I figured, hey, why not just remove the FPR line all together?! As I did so, my block 32 readings went up to 3.2% in about 2 minutes! Yeah! I am now in the recommended value! Took it for a drive and noticed I am NOW requesting 2250mbar of boost which is VERY close to where I should be! THEN my laptop died... Crap... So, is it my FPR or am I just covering up something else? What exactly did I do there? I cannot do any more logging until my battery charges dammit!

[Nebone]

If you removed that line, did you cover the IM nipple? I had a small hose fall of from the front of the IM during the Waterfest Cruise and I ended up with a nice 5 psi. Random discovery there and you might be on your way to solving the issue.

[k0mpresd]

hell yes. who needs fuel pressure to rise with boost anyways. just make the ecu adapt it back in. haha.

[Ewok_Fetus]

Well, that is the thing, I DIDN'T need the fuel pressure to rise... I have read somewhere that the 2001 02 sensor's can only read 10.8:1 AFR... My car was actually REQUESTING an AFR of 9.8:1 which is too rich and causing problems... I am still thinking my FPR is shot even though I replaced it two years ago... Which shortly there after, by a few months, my car started to drop boost... It is a 4 bar bosch FPR...

[Ewok_Fetus]

Bump,














(I am sure if I said something about 20's on an A4 or a BT, I would get more love!)

[mike-2ptzero]

Well your numbers went up because your fuel pressure went up once you pulled that vac line off and when you drove it the car ran much leaner on its own since the fuel pressure stayed at a set value instead of increasing which means your injectors were spraying less fuel. I dont think you really found anything. Only way your FPR would be bad is if for some reason it is increasing the fuel pressure more then 1:1 vs the boost. You could always try switching to another 4 bar or add a fuel pressure gauge so that you can see if the pressure is going up more then 1:1.

[Ewok_Fetus]

Then why in the hell is my car requesting less boost when rich and more boost when lean? I don't get that...

[djwimbo]

Then why in the hell is my car requesting less boost when rich and more boost when lean? I don't get that...

It's probably trying to save it's ass.

Install a fuel pressure gauge. You can do it for pretty cheap, or you can actually get an electronic gauge and put it inside the car. I installed a barb fitting w/ an 1/8" NPT tap to check mine once in awhile.

I did this awhile ago... here's my results

Yesterday I tapped into my fuel line and monitored my fuel pressure while driving.
Idle: ~48psi
light accel: 52-55psi
full boost: 70psi peak and 5K-redline it will lower down to 63-64psi
high vacuum/hard engine braking: 43-44psi

Basically that's "normal". With the vac line removed from the FPR you should be in the range of 56-58psi.

[mike-2ptzero]

Well he just needs a analog gauge that uses a sender and wires. Install the sender just like you would a inline pressure gauge, ground the body of the sender and then wire up the sender to the gauge like normal. I had one in my car but took it out because I already had a electric sender to my LM1 for logging.

[djwimbo]

Sorry, I didn't mean electrical display, I meant using an electrical sending unit.

We had one on the Vette, nice to keep an eye on if you're stretching out the gears.

[Ewok_Fetus]

Let's just say my fuel pressure is high... FPR?

[djwimbo]

How high? 90+psi? If so the bypass valve in the pump is probably opening to prevent it from going any higher.

I'd remove the FPR and make sure it's not stuck shut. Then again, I'd probably replace it either way.

[Ewok_Fetus]

How can I tell if it is stuck? I honestly think *hope* that this is my problem...

[Ewok_Fetus]

Just thought of something... If it is stuck, wouldn't my car run the same with the vacuum line removed?

[djwimbo]

If you have a vacuum pump(hand pump) you can look at the bottom of the regulator. When you pump up the vacuum, the diaphragm should open. This would allow the fuel to return to the tank through the bottom of the regulator.

You should be able to see the diaphragm as seen here... Fuel flows through it, so it should be visible.

[djwimbo]

Just thought of something... If it is stuck, wouldn't my car run the same with the vacuum line removed?

If it were stuck shut you'd be running rich(numerically low AFR) all the time. If it were stuck open, you'd run lean anytime you'd see anything but vacuum in the intake.

If you remove the vacuum line, all you have is Atm. pressure on the FPR. Without the assistance of boost, your fuel pressure will not rise as your boost does. This also includes idle/vacuum situations. Vacuum at the FPR will decrease fuel pressure. Ideally if you removed the vacuum/boost line from the FPR you would run rich at idle/vac and lean in boost. This of course is presuming the regulator is suppling proper pressure at atm pressure.

[mike-2ptzero]

I would just try to find someone near you that is also running a 4 bar and swap it into your car to see if it runs any different.

[Ewok_Fetus]

My only problem is removing the regulator without damaging it... It was "TIGHT" last time I tried to do anything...

[Ewok_Fetus]

Well, I went out and looked at it... I guess the original one was the only hard part to get out... I guess the gunk kinda make it a bitch to get out, this one was easy!

I looked and there was no diaphram... I removed the screen at the bottom and only found a round metal part in there... It wouldn't budge with vacuum or pressure... At least I couldn't see it if it did...

[ModifiedA4]

you can't see the diaphram...its too buried inside.

[Side-Step]

What should the FPR be set at with and without vac.? I've been playing with ours for awhile. The car seems to smell gassy when you wait for the few minutes to let everything cool down from driving.
My LM1 reads high 14's to low 18's at idle and full boost (21psi) is 11 to 12. I'm thinking that is good, but I could use some advice.