• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

*new* injectors are here

imma honky

NAXJA Forum User
Location
Augusta, Ga
Finally recieved my ford injectors (#19) orange.....
They had around 90k miles on then (89 mustang)....

What ALL do I need to do to the injectors/ engine before and when installing them??

Wanna get this done the right way, and do it only once..... It was a set of 8 for 40 bucks.

Im guessing I should get them cleaned? And I heard or read they they should be balanced???(i dunno)

Any info, suggestions......



PS. Jeep is still on stands till new alternator arrives.
 
I did this last year.Fairly simple.Disconnect fuel line,remove fuel rail,remove old injectors then reverse.

Tip:use some KY to lube the new o-rings

and if you're gonna balance them be sure to check the blicker fluid
 
Did I miss something here?

What are you doing now? Thread hyjack, what is the difference between the Ford and Jeep injectors? I would assume the Ford's are bigger? Are the 4.0L injectors bigger or the same as the 2.5L injectors? You got me thinking!
 
switching to the mustang #19 injectors adds a little more oomph (not much at all actually) but from what i hear, it also helps some rough idles. It basically a nice upgrade for the 4.0.....Im not sure if you would put them on a a 2.5.....you may wanna ask first. Also, for 40 bucks for 8 used ones is a helluva lot cheaper than 70 per new stock!

oh yeah, greedy.... i wont be doing the clean/balance myslelf......so I dunno what "blicker fluid" is...

ps. ive called one place that claimed to do injector work, and he said he had never heard of balancing.....should I be worried?
 
Blinker fluid and balancing injectors is like.....

Hauling motorcycle doors..... :) So the Fords have a higher Lb rating. What is the stock Jeep injector rated at?
 
doh...ya got me!

I "think" stock (non HO)4L injectors are around 17-18 Lbs.....key word is think......
 
I have a list of injector sizes on this page of my website:

http://www.jeep4.0performance.4mg.com/tech_specs.html

The 4.0 non-HO injectors are rated at 18.6lb/hr at 39psi and the Ford's are slightly higher at 19lb. Because their resistance values are very similar and they're also the same physical size, the Fords are a straight swap in. They're popular because they're cheaper than the stock Jeep injectors and they also have a wider spray pattern that helps to atomize the fuel better.
 
Damn Dr. you some serious info there.....

What about the 94 2.5L? Any idea on there injector size? They are red and black.
 
The benefit really lies in better atomization, not more fuel per se...
Let me paraphrase my Friend Ted Breaux concerning bigger injectors...

When selecting fuel injector size, one has to consider several important factors if the vehicle is to be capable of delivering the necessary fuel, but having enough low speed resolution to deliver good economy. The first and foremost will be what kind of power the motor is projected to make. A good port injected engine will absolutely require 0.45 lb fuel/hp/hr for adequate air/fuel ratio at max power. Also, injectors begin to sacrifice efficiency once they exceed about 70% of the design rating (due to increasing pulse lengths). Again, also, the injectors are designed to deliver best atomization at the designed pressure, and either raising or lowering the pressure will adversely affect this. With the [pre HO XJ], the engine was designed to make 180bhp. If we take a 19 lb/hr injectors and divide by 0.45, we get 42.2hp per cylinder. Multiply this by 6 cylinders, and we get 252bhp static (injector open all the time). We know that the injectors will begin to lose efficiency once they exceed 70% of 252, which yields 177bhp.

Pretty damn close...ASSUMING your injectors are clean!

a 24# injector will run 224hp at 70%...More than any bolt on guy can get out of an internally stock 4.0.
 
Balancing injectors is typically something only done for real high-performance engines, and is vaguely similar to balancing carburettors (not to be confused with "phasing" - something else entirely, and material for another class.)

When injectors are balanced, they are basically put into a test jig and the flow rates are tested - making sure they are within, say, 10% of each other to prevent a cylinder running excessively rich or lean. It's similar to doing a compression test - the nominal compression figure is less important than consistency across the scale.

Even on performance engine, a gross injector balance of 3-5% is considered acceptable, and the tightest I've ever heard of injectors being rated for consistency is only 2% (which is still pretty wide.)

For a production engine, DFWAI. You'll spend a lot of money to do it, and it's not an issue for you to worry about (our 4.0's run too far from the bleeding edge anyhow.)

Get them cleaned and pop them in - keep the other two as spares. As long as they're all from the same set, you'll be fine.

5-90
 
So back to my question....

What are the 2.5L ijectors rated at or where would I find the info? When I put a cam in the engine would changing the injectors help too?
 
Tozovr, thank you! You explained that perfectly in my terms (lamens). now I understand.

5-90, Thats exactly what I needed to know. Go figure the reason he (my fiend) told me to get them balanced is b/c he used to work on RX-7's and old mustangs.

NOW. Are there going to be anything problems I might encounter when removing the fuel rail for transplant? Also, by rail is looking pretty shoddy. If it is within a reasonable price, where could I pick up a new one?
 
imma honky said:
oh yeah, greedy.... i wont be doing the clean/balance myslelf......so I dunno what "blicker fluid" is...
It's blinker fluid, and check the fuse in the radiator :D
 
You might want to dribble a little oil on the bottom injector rings and let them soften up a bit before you pull them - just in case. I use a couple drops of ATF per ring for about a minute before I wiggle them out.

Don't try to pull them straight out, but wiggle them out a bit as you gently pull. Make sure you have the fuel rail all unbolted (Renix rails are retained with four bolts, threaded 5/16"-18) and you can leave the topside retaining clips in until you get the rail assembly out. Take the rail to bits once you have it on the bench.

Use new o-rings for assembly, drop them into a short cupful of gasoline before you start the job. Let them soak in that while you work, and don't put the rail together until you are SURE you can have it sorted within a few minutes. That's the best way I've found to do this job, and I've done it a few times. Soaking the orings in gasoline softens them just enough to keep them from getting skinned on the way in, and they'll seal up nice as well.

It will take longer to take the rail to bits than to put it together, and I'd suggest checking all the oring seats (use a flashlight) for any remnants that may need to be cleaned away before installing. Oddly enough, a bronze brush works best - I used an old 12 gage shotgun brush on mine!

Figure a little over an hour or so, if everything goes just so.

5-90
 
TOZOVR said:
.......a 24# injector will run 224hp at 70%...More than any bolt on guy can get out of an internally stock 4.0.

Actually I was running at about 225hp with all the bolt-on mods before I installed my ported head. I already had Ford 24lb injectors at that time and my engine was running rich. I thought that the extra airflow from the ported head would cure that but while it did improve things slightly, the engine still ran rich even at the 240hp level.
I finally cured the richness by making a homebrew MAP adjuster and I gradually reduced the input voltage from 5.0v to 4.2v to get the A/F mixture on the lean edge of stoichiometric. That can only mean that I'd made the engine so efficient that it could produce more HP/TQ from less fuel.
I calculated that at the 5000rpm peak HP point, my injectors would have to be operating at a mere 70% duty cycle to produce an A/F ratio of 13.0:1 at WOT, with a BSFC of 0.421lb/hp. The stock 21lb injectors would be operating at a still acceptable 80% if I had those instead of the 24lb'ers.
The bottom line is that the 4.0 engine can be made to be more efficient than you'd think, so don't get caught in the trap of fitting too large injectors. A MAP adjuster together with stock injectors might be all that you need to fine tune the A/F mixtures when you've added some airflow-enhancing mods.
 
Dr. Dyno said:
Actually I was running at about 225hp with all the bolt-on mods before I installed my ported head. I already had Ford 24lb injectors at that time and my engine was running rich. I thought that the extra airflow from the ported head would cure that but while it did improve things slightly, the engine still ran rich even at the 240hp level.
I finally cured the richness by making a homebrew MAP adjuster and I gradually reduced the input voltage from 5.0v to 4.2v to get the A/F mixture on the lean edge of stoichiometric. That can only mean that I'd made the engine so efficient that it could produce more HP/TQ from less fuel.
I calculated that at the 5000rpm peak HP point, my injectors would have to be operating at a mere 70% duty cycle to produce an A/F ratio of 13.0:1 at WOT, with a BSFC of 0.421lb/hp. The stock 21lb injectors would be operating at a still acceptable 80% if I had those instead of the 24lb'ers.
The bottom line is that the 4.0 engine can be made to be more efficient than you'd think, so don't get caught in the trap of fitting too large injectors. A MAP adjuster together with stock injectors might be all that you need to fine tune the A/F mixtures when you've added some airflow-enhancing mods.

Dino, I don't want to sound like an ass, But Prove It. I want Duno Numbers not gleaned from A computer program and a handheld stopwatch.

No Offense intended, but a handheld unit is nowhere near as accurate as an accellerometer (Vericom or Gtech), a DynoJet, or even your time figured using actual dragstrip times and the weight of the rig. You have HUGE variables in your data with the stopwatch.

Even small variables when figuring HP with formulae reenders it bunk.

I am in No way stating that you haven't completely optimised the 4.0 in your XJ, HELL NO! But take the same time and care you put into tightening tolerances and optimising your XJ, and put that into proper testing and empirical data collection.

Cheers!

RJ
 
$40 bucks for 8. My local wants $15 each for Jeepers. :(

He also said he can't keep the Ford injectors "in stock" because of the high demand due to leakers. I wonder if people are just missing the boat and not replacing o-rings, or . . .

$15 x 100% mark up x 8 injectors = $240 for "leaking injector parts" plus labor @ same = $480 + bench parts + new o-rings ($20) = I need to start a shop. :D
 
ebay ebay ebay!
Got em off ebay for the 40$. Guy had really good feedback which is why I got em.
 
Toz, you make some valid points but I'm 700 miles away from the nearest chassis dyno so I can't quote actual dyno numbers. I wish I could. Remember that even chassis dyno results can vary between dyno runs done on the same vehicle under the same conditions, and from dyno to dyno. If you want truly accurate HP/TQ numbers, the only place you're gonna get them is on an engine dyno.
You might question the accuracy of my stopwatch times but I've done it so many times over the years that the results I get are very consistent, so there's not as much variance as you might think. Even the G-Tech is prone to some error. The only truly accurate 1/4 mile times are going to come from the dragstrip or a Vericom.
I'm not going to claim that my HP/TQ numbers are totally accurate but I don't think they're off by more than 3%. That's close enough for me.
My 4.0 is running very well indeed but I don't think it's completely optimized. The only way I can do that is to get a fully mapped custom chip burnt and installed in my PCM. Nevertheless I've been getting a consistent 20-22mpg since I dialed in my MAP adjuster (nearly 2mpg better than before) so I must be doing something right.
You can either consider me a genius or think of me as a stupid git who doesn't know what the hell he's talking about. ;)
 
Last edited:
Back
Top