4.0L OBD1 fuel pressure?

[Raisins78]

Hey again.
Does anyone know what the factory fuel rail pressure is?
I have just replaced my pressure reg (leaking) with an aftermarket adjustable setup.
I had approx 38psi before hand, but have set it to 40psi with the new one....
Not sure if the before pressure is accurate due to it leaking.
Does anyone have that info?
p.s......it runs smoother now since its not pumping fuel down the vacuum reference line lol.

Ill chuck a photo up tomorrow when its daylight

[rainman]

31pis @ idle
39psi at wide open throttel ( or at idle with the vac hose disconnected and the vac line pluged.)

[Raisins78]

I can only see approx 4psi change between idle and WOT.
I have adjusted it now to 38psi idle (nudges 42psi WOT)

[Raisins78]

here is a pic for those wondering.

[rainman]

did you drill the guts out of the original FPR or somthing?
cause if not with no vac on the back of the OEM fpr diaphram it will cause 39psi in the fuel rail (or it should if working correctly.)
you realy need 31 at idle and 39 at wide open throtle, give or take - the WOT condition can be simulated at idle with the fpr vac line disconected & blanked off.
ALL of the computer fuleing callculations are done under that assumption. as described it will run ritch.

IMHO Ditch the off rail fpr and get a new fpr. if you have to have have an adjustable one get one that replaces the oem unit. less hoses less connections less fire risk.
all coverd here: towards the end of the first post.
http://www.ausjeepoffroad.com/forum/showthread.php?t=92236

Good luck with it.

[rainman]

Just thinking about it if you pull the oem fpr and reinstall it with out the the small oring, you should be able to get the 31 & 39 you require with the off rail FPR.

[Raisins78]

I tested it before i removed it. I was getting 35psi at idle, and nudging 40psi at WOT (settling back to 38-39psi as the revs increased)
I have never seen a regulator that moves 8psi from idle to WOT, other than rising rate ones/aftermarket etc.
It idles way smoother now with the adjustable set at 40psi WOT.

p.s. I cut the plunger out of the factory reg, sealed it and bolted it back on. so its full flow to the new one.
1-2 psi increase should be able to be trimmed by the computer i assume. It should lean the tune back a touch to keep O2 readings within spec.
Higher pressure means better fuel atomization, so with slightly higher rail pressure I should see better spray pattern, less injector opening times and better economy (well it has worked for my last 2 EFI Cars.)
If you increase the pressure too much, you can damge injectors, seals and push the fuel map beyond its safe limit causing fault codes.
I changed my VN V6 one to an adjustable, set it at 45psi (40psi from the factory) and seen a 1-2L/100km improvement, with no other mods (was doing 1500km a week highway at the time)
Stock it was getting 8.5-9L/100km, cruise set at 110km from Albury to Newcastle
After pressure reg swap I seen 7-8L/100km for the next 200,000km's....

I will reset the factory Jeep ECU and see how it goes.