Fuel pressure question

[WLD747]

still not 100% sure, but would increasing the fuel pressure (rising rate) lower the duty required but the injector or increase it?

[ricknismo]

At a guess I'd say decrease it as its the same as making the equal to a bigger capacity..ie 440cc up to 480cc

[netrati]

Yes if you increase fuel pressure it will decrease the required injector duty cycle.

[blind_elk]

Changing the fuel pressure WILL NOT alter the duty cycle (although it will alter the REQUIRED duty cycle, but you have to change that). All it will alter is the amount of fuel that gets injected during the "injector open" period.

If you back off the base pressure, then you will effectively lean off the mixture. If you increase the pressure, you will richen the mixture.

The copious quantities of black coming from the exhaust suggest you need to reduce the pressure a bit.

[ylwgtr2]

OMG....talk about people making things difficult with all this consult bullshit and guessing ect..........heres what you do....underneath the steering column theres a small trap door....open this and you will see a connector....Here is a dodgy pic i took from the R34 GTR factory schematic book.....if you momentary earth out he test wire the vehicle will enter diagnosis mode....the engine check light on the dash will give you a series of flashes....eg on once then on four times is code 14....once you have done a decode post up the code and i will tell you what it means.....on 34 GTR's you can also switch the dash meter into a sensor diagnosis mode...you do this by holding the two outside buttons down while turning the ignition switch on.....then when the GTR emblem comes up push the toggle switch 5 times....you can now check the operation of the TPS and the other sensors....if you have the nismo upgrade you can hook up your laptop and see it all working....

check you fuel pressure at idle and on boost with the appropriate test gauge....from all the info here you should be able to directly pinpoint the problem

[ricknismo]

CHK the test wire?

[ylwgtr2]

yes.....

[ricknismo]

Any particular stage, I tried every thing, nothing happens.

Start the car...earth the chk to earth...right??

nothing

[ylwgtr2]

ascut and pasted from the other thread..........

link test terminal with the "-" terminal....turn the ignition on....then remove the the link....then your code will be displayed

if you got a power FC it wont work.....dude its really not that hard....if your still having dramas pm me and i will give you my number and talk you through it.....

[ricknismo]

Finally got new o2 sensors in...dear suckers..The others rattled and didn't register any volts.

Now it registers volts but only upto 1 v and the duty cycle still goes through the roof at high revs.

Don't the o2 sensors go to 5 volts?

[anyjapspares]

my car was blowin copious amounts of black smoke on high revs, yet was makin f**k all fuel pressure, replaced pump ... all fixed

[rob82]

The smoke you were seeing was propably from it leaning out and pinging its nuts off.

[ricknismo]

ended up my prob was simply the oxygen sensors