Fuel Injector & Pressure Questions

I'm about to swap a 99+ intake manifold on my 95 4.0 (with a Borla header) and have a few of questions. I search around and got some info that just added to me confusion

The new manifold came with a fuel rail and injectors. It looks like the new fuel rail is significantly different in the old one so I need to reuse the 95 fuel rail. According to my searches the new injectors flow more but at a higher pressure:

95 53030343 Tan 39psi 21.0lb/hr
99+ 04854181 Blue tip 49psi 22.5lb/hr

Does this mean that I need to have a higher fuel pressure (49psi vs 39psi) to run the new, higher flow injectors.? Can this higher pressure be obtainaed with just a higher pressure regulator or is a new pump needed?

You probably got those injector flow numbers and pressures from my site. My suggestion would be to use the '95 fuel rail, '95 regulator, and '95 injectors with new o-rings to keep things simple and save yourself a lot of grief. If you use the later-style injectors, you might run into the following problems:

1. 39psi might not be enough to atomize the fuel properly. The 49psi fuel pressure regulator is in the tank so using it isn't an option, therefore the only other choice would be to stump up 189 buckaroos for Hesco's adjustable unit.
2. Your '95 injector harnesses won't plug properly onto the injectors (Markus aka Gojeep knows about that one). One solution is to ziptie them but they could come off again and that would be a PITA. The other is to cut the old harnesses off and splice in the newer ones.

If your '95 injectors are still the original factory items, ditch them and replace them with a set of Accel 21lb'ers. You can sell the newer injectors in e-bay to recoup some of the cost.

Dr. Dyno said:

You probably got those injector flow numbers and pressures from my site. My suggestion would be to use the '95 fuel rail, '95 regulator, and '95 injectors with new o-rings to keep things simple and save yourself a lot of grief. If you use the later-style injectors, you might run into the following problems:

1. 39psi might not be enough to atomize the fuel properly. The 49psi fuel pressure regulator is in the tank so using it isn't an option, therefore the only other choice would be to stump up 189 buckaroos for Hesco's adjustable unit.
2. Your '95 injector harnesses won't plug properly onto the injectors (Markus aka Gojeep knows about that one). One solution is to ziptie them but they could come off again and that would be a PITA. The other is to cut the old harnesses off and splice in the newer ones.

If your '95 injectors are still the original factory items, ditch them and replace them with a set of Accel 21lb'ers. You can sell the newer injectors in e-bay to recoup some of the cost.

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I actually snagged the injector flow numbers from a post here that I'm sure was nabbed from your site

Your reply was pretty much what I was thinking and it's good to get confirmation. I'm into this for too much $ right now so I'll stick with my old '95 injectors and press reg. for now.

Thanks!

Been there done it you will only have one problem and that is if you have some sort of intake(air) plus you headers you're gonna run lean and Im talking real lean...I popped for the hesco unit due to the fact that I could push the temp into 220 just by jumping into the gas from a stoplight to stoplight and it was hot before I got to the next light..Results may vary but that is the general consensus(sp?) The good thing is to get a 62mm throttle body while your at it, I got mine from fastman(work of art, great guy to deal with) get the fuel pressure reg from hesco and call it done...

Oh yeah your also gonna need to change out the ps pump as the 95 wont work with the new manifold, I got a reman from a 97 make sure and use a newer ps pulley as well otherwise your never gonna get the damn thing mounted...

Also you need to change the belt to a 99+ as well the 95 will be too long and I hope you got the adjuster bracket for the 99 manifold???
Any more Q's just ask it sits in my driveway so I can check for reference..

has anyone considered using a fuel filter/regulator assembly for an 03 grand cherokee?the regulator is in the filter.i converted mine to use the filt/reg assembly cause i changed the intake to a 99 style with a returnless fuel rail i opted to keep the returnless system for the benifit of not having heated fuel return to the tank so i always have cool fuel going to engine.

oh yeah forgot to mention i made a map adjuster to adjust air/fuel ratio. $53 for filter/reg at dealer $12 at radio shack for parts to make adjuster = $65 plus misc hoses and clamps to relocate return line at the filter $10 totaling $75 much less than priceco adjust regulator:laugh3:

I began the swap last night. I pulled everything off and cleaned up the new intake. I need to pick up a new O2 sensor tonight and hopefully get it back together.

I'm going to modify the original PS pump backet like this guy did:

http://www.jeepforum.com/forum/showthread.php?t=215685&highlight="intake+manifold"

I'm going to just use the old injectors for now and keep an eye on the temp. Swapping to the new style factory regulator seems like a huge hassle. Isn't the filter/reg in the gas tank? I'll most likely go for an adjustable regulator or the Accel injectors.

BTW, did you folks use anything on the gasket when you did the swap or install it dry? The FSM doesn't mention using anything and the original appears to have be installed dry.

stoneattic said:

I began the swap last night. I pulled everything off and cleaned up the new intake. I need to pick up a new O2 sensor tonight and hopefully get it back together.

I'm going to modify the original PS pump backet like this guy did:

http://www.jeepforum.com/forum/showthread.php?t=215685&highlight=%22intake+manifold%22

I'm going to just use the old injectors for now and keep an eye on the temp. Swapping to the new style factory regulator seems like a huge hassle. Isn't the filter/reg in the gas tank? I'll most likely go for an adjustable regulator or the Accel injectors.

BTW, did you folks use anything on the gasket when you did the swap or install it dry? The FSM doesn't mention using anything and the original appears to have be installed dry.

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I would wipe a film of moter oil on them to keep them from sticking and rolling out of the little groove they sit in.

EDIT: never mind I thought you where talking about the injectors themselves.

On mine, I used the copper spray sealer thats for intake and exhaust gaskets. Get it at Napa or most auto stores. Spray both sides of the gasket, then assemble.

I am in the same boat. I have an intake manifold from an 00' I believe on the way. I was wondering: 1) Can I put into a 95 4.0 HO? 2) What will need to be done for it to mate up. Without having to cut/grind parts?

Thanks,
Silent

Silent said:

I am in the same boat. I have an intake manifold from an 00' I believe on the way. I was wondering: 1) Can I put into a 95 4.0 HO? 2) What will need to be done for it to mate up. Without having to cut/grind parts?

Thanks,
Silent

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I'm taking a break right now but I have the header and intake on. I'm modifying the PS pump bracket to work similar to the link I posted above. So far it's been smooth sailing. I was even able to install the manifold and header from top

I'll let you know how it works out. I probably won't get a chance to finish it until the weekend though

a hassle? all you do is install the filter/regulator assembly in place of the original external fuel filter.no need to pull tank and install it like on the 01 xj cherokee model.very easy to do.

In case you haven't already read this, go here:
http://www.naxja.org/forum/showthread.php?t=62480&page=1&pp=15&highlight=corbinafly
and read posts #7 and #12. That's what I did to my 95 when I did the swap.
I'm curious to know if the Borla will interfere with the newer intake like it did on mine.

Hope it helps.

Kyung

markaboo929 said:

a hassle? all you do is install the filter/regulator assembly in place of the original external fuel filter.no need to pull tank and install it like on the 01 xj cherokee model.very easy to do.

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I didn't realize that. I assumed it would have to go into the tank like the newer models.

corbinafly said:

In case you haven't already read this, go here:
http://www.naxja.org/forum/showthre...ight=corbinafly
and read posts #7 and #12. That's what I did to my 95 when I did the swap.
I'm curious to know if the Borla will interfere with the newer intake like it did on mine.

Click to expand...

No problems with the Borla fitting at all. I've got the manifold, header and PS pump all mounted and adjusted. I just need to install the fuel rail, electrical and vacuum connections and run the new exhaust. Alomst there.

stoneattic said:

I didn't realize that. I assumed it would have to go into the tank like the newer models.



No problems with the Borla fitting at all. I've got the manifold, header and PS pump all mounted and adjusted. I just need to install the fuel rail, electrical and vacuum connections and run the new exhaust. Alomst there.

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Are you sure that they're not touching each other at all? Mine went on fine too, but I noticed a loud ticking noise coming from the area between the intake and exhaust manifolds when I turned the motor off and the exhaust was cooling down. It took me a little while to figure out where the noise was coming from. I found it by trying to slide a piece of thin cardboard between the intake and the suspected exhaust runner. It wouldn't fit. Then I tried with a piece of thin paper and it still didn't fit, so I knew for sure that they were interfering with each other.
Hopefully you're right and yours is fine which would mean that either all Borla headers for 95 model year and/or all 99+ intakes vary slightly in shape.

Kyung