HO Fuel rail Regulator questions

I've been having some issues with my rig. I've been trying to figure out a O2 sensor problem and what might be causing it. I have a Renix computer, block, head, and exhaust manifold. I have a HO Intake manifold with an HO TB and a HO Fuel rail with HO injectors. I took this stuff from a donor xj i have and so I had all of the steel fuel lines so I installed those all the way to the tank with a new fuel filter. Problem is that I think the jeep is running rich. I adapted the renix TPS to the HO TB and it's set at .8 volts Idle. The MAP at Idle is around 2V. Do you think the fuel PR could be stuck? I can remove the vacum line and pinch it off and there is no noticable difference at Idle or while giving it throttle.

How would I go about testing the pressure on the HO fuel rail? I don't see a test port. What SHOULD the pressure be?

Thanks
Adam

For RENIX, spec is 39psig with the vacuum disconnected from the regulator, and intake pressure + ~31, IIRC, with the regulator hooked up.

Since you have appanently deleted the regulator, the computer could be getting confused by the fuel delivery rate (as I am inclined to recall, the HO regulators supply a constant pressure, while RENIX is modulated by intake vacuum.)

You might want to look into adding a fuel pressure regulator that features a vacuum sense port - sort of like the old "rising rate" pressure regulators that used to be put on turbocharged engines. Most aftermarket regulators are also adjustable, so you can fine-tune afterwards.

I think Marren Fuel Injection has some - Google them, because I don't recall the URL offhand...

5-90

5-90 The HO rail had a Vacum port right on the regulator. I didn't delete the HO reg. I'm thinking that maybe the HO is rated for a higher pressure?? Don't you think that with the vacum line disconnected from the reg that SOMETHING would change? I'm going to unplug the return line and put a hose on it going into a bucket to see if any fuel comes out, and if so how much. Any Ideas on how to test the pressure on that HO rail?

Thanks a lot
Adam

IF it is, it's not much. RENIX injectors are rated for delivery at 39psig, and I'm thinking that HO units were rated at 39 or 41psig - not a significant difference, unless I do the math and find out otherwise (but I somehow don't think so.)

Disconnecting the vacuum port should raise the pressure - the regulator output pressure is/was biased by manifold vacuum, which is why I'd mentioned two different specifications.

As far as checking it out, I'm not sure how to do that without adding a port. RENIX had the test port right on the fuel rail (a big Schrader valve, like GM uses,) which simplified things immensely. I'm not sure about HO - I can check the 1991 and 1994 FSMs I have when I get back (in an hour or so...)

5-90

5-90 said:

IF it is, it's not much. RENIX injectors are rated for delivery at 39psig, and I'm thinking that HO units were rated at 39 or 41psig - not a significant difference, unless I do the math and find out otherwise (but I somehow don't think so.)

Disconnecting the vacuum port should raise the pressure - the regulator output pressure is/was biased by manifold vacuum, which is why I'd mentioned two different specifications.

As far as checking it out, I'm not sure how to do that without adding a port. RENIX had the test port right on the fuel rail (a big Schrader valve, like GM uses,) which simplified things immensely. I'm not sure about HO - I can check the 1991 and 1994 FSMs I have when I get back (in an hour or so...)

5-90

Click to expand...

the HO FPRs are 39 psi, in 96, they were upped to 49psi, but thats managed at the pump

Adam90xj said:

I've been having some issues with my rig. I've been trying to figure out a O2 sensor problem and what might be causing it. I have a Renix computer, block, head, and exhaust manifold. I have a HO Intake manifold with an HO TB and a HO Fuel rail with HO injectors. I took this stuff from a donor xj i have and so I had all of the steel fuel lines so I installed those all the way to the tank with a new fuel filter. Problem is that I think the jeep is running rich. I adapted the renix TPS to the HO TB and it's set at .8 volts Idle. The MAP at Idle is around 2V. Do you think the fuel PR could be stuck? I can remove the vacum line and pinch it off and there is no noticable difference at Idle or while giving it throttle.

How would I go about testing the pressure on the HO fuel rail? I don't see a test port. What SHOULD the pressure be?

Thanks
Adam

Click to expand...

how do you now its running rich, does it do it through the powerband?

auto or manual?

It has an AW4. That's why i had to adapt the tps onto the new intake. I don't know for sure that it's running rich. I can't seem to get the O2 sensor to give an accurate reading. I'm tempted to add another o2 bung and put a one-wire sensor in there so I can just monitor the 0-1v swing. (of course leaving the other sensor connected) The reason i think it's running rich is that there is a much stronger exhaust smell (meaning smells rich) and I believe it's getting terrible fuel milage. I don't know what it's getting because I have only been driving it around a little bit as it's not my DD. Pretty much what i'm assuming is that either A) something is FUBR with the o2 sensor. (i've tried 3 diff. sensors so far) B) the computer is FUBR (tried 2 of those) C) there is a sensor that is FUBR (double checked every darn one of them) D) I shouldn't worry about it.

If you have any other ideas please post up !!

Thanks for the help guys....

Adam

well i had a similar issue, i tried to run 96+ injectors, with the 39psi regulator

the 96 injectors require 49psi to atomize the fuel correctly, the 39psi was actually spraying liquid, making the O2, computer, and a/f gauge i have read rich. It smelled rich, etc etc. when in reality, it was running lean

how can you tell what year injectors are what. I'm 98% sure the rail I used is out of a 92 but there's always something that can happen.

I'm putting it on a computer tomarrow to see what the ECU is doing.... HOPEFULLY it'll tell me something is wrong and what it might be

Later
Adam

Adam90xj said:

how can you tell what year injectors are what. I'm 98% sure the rail I used is out of a 92 but there's always something that can happen.

I'm putting it on a computer tomarrow to see what the ECU is doing.... HOPEFULLY it'll tell me something is wrong and what it might be

Later
Adam

Click to expand...

if the rail has the FPR on it, then its a 39psi set up

do you have the vac hooked up to the FPR?

Yes, vac line is hooked up and that makes sense as 96+ are regulated at the pump. Thanks


Adam

Ok, so HO fuel injectors are not the same as RENIX injectors. I put the jeep on a scanner and I had a ST trim of around 30 and a LT trim of 104. Should be 128. I swapped in the old injectors into the ho rail and runs great now.

So maybe I can save a little fuel $$$ on the way to riverrock tomarrow then Tellico on sunday (about 550 miles one way)

Later
Adam