Checked Fuel Pressure Today

[FORSFED]

Well I rigged my gauge up to the windshield and here are the things I noticed.

- Base pressure was 42psi
- car has vac reading of 16 and raising it to 0 the pressure stayed at 42 and didn't raise 8 psi like I believe it should have. (probably due to the walbro 255 pump flowing more at idle....)
- At 10psi of boost, fuel pressure was 52psi
- Boost creeped due to 2.5" exhaust and fuel pressure increased with it.
- Car spools to 10psi by 3k, but misfire keeps occuring around 4800rpm, long after it's been at 10psi
- A/F ratio stays right around .9V and does not drop or increase
- minimal counts of knock ( 4-5 counts max)
- no timing retardation

only mods are 2.5" catback exhaust and walbro 255 pump

I'm thinking that this is too high of pressure and volume for the stock setup and that I'd need an adjustable regulator to lower the pressure down a ways...

[JET]

What car? 43 psi is right for a 2g, 38 psi for a 1g.

[FORSFED]

It's a 1g.

[Pushit2.0]

plugs, wires, coil pack, bad grounds, bad gas, boost leak, clogged fuel filter, a problem with the turbo. It could be a few things. Fuel pressure sounds normal for a 255 and stock regulator.

~John

[A//// Guy]

I think you should post what you have done already, as many many of the things people will suggest were already mentioned in five other threads on this same topic.

Im assuming all the basics were done... (johns post)

[FORSFED]

Good Idea, I forgot not everyone knows what I've tried....

plugs
wires
coil pack
transistor
injectors
fpr
fuel filter
fuel pump
mas
fixed vacuum leaks
cbv
tps
cas
ecu

I think that's it, there might be something I've forgotten, but that about sums it up. Reason I think the pressure's too high is because when I disconnected the fpr vacuum hose it didn't misfire once....therefore lowering the pressure while making sure not to go too lean should fix my problem.

[Shane@DBPerformance]

What is the problem with the car? And how did unplugging the FPR line help exactly? I thought it ran the same pressure at 0 psi as at -16 vacuum. did you boost with the line unplugged or something?

[Pushit2.0]

Then you need to buy a realy fuel pressure regulator, or turn the boost up. You could also use a wideband o2 sensor for tuning, it is my guess you are running WAY to rich if you only have exaust and a fuel pump. mo boost or a real FPR.

~John
ps. the B&M is a waist.

[FORSFED]

The problem with the car is that it severely misfires in every gear from ~4800 rpm's and up. The car does run the same fuel pressure regardless of whether there is 16-18psi of vacuum or there is 0, the fuel pressure always remains at 42psi, but it does rise to 52psi with 10lbs of boost so I know the fpr is doing its job. Then out of curiosity I unplugged the vac line on the fpr, and the fuel pressure naturally stayed at 42psi even when I stepped on it with 10lbs of boost. It ran fine up to redline like this, so I've been able to determine that there's too much fuel, and with that I planned on getting myself a regulator as john suggested and a boost controller is on the way too. Once I have these things it'll be a matter of fine tuning it so that the fuel curve is linear and the car doesn't run too righ or too lean anymore. Basically I was just looking for some input from you guys to see what your thoughts and suggestions were, that is why I keep posting what I've been doing and what has resulted.

[Shane@DBPerformance]

Maybe pull the lower honeycomb out of your MAS, that should make it run a little leaner across the board.