How to change your Injectors - 1998 Jeep Cherokee - 4.0L

[Mudderoy]

http://xjtalk.com/images/special/jeepinjector9.jpg

At 150k+ miles and a MPG issue that won't improve I decided to take the plunge and replace my injectors.

I found some Ford 9L3E-E7A 24lb Injectors for $69.50 on eBay.
These are EV6 and the Jeep is a EV1 connector on the harness. So I purchased some adapters.
You can get some connectors off a Mustang and just splice them in if you like, but I wanted the ability to use either EV1 or EV6 injectors.

All in all the injector swap was easy, and total time (my first time to ever do an injector swap) was 1.5 hours,
and that included taking pictures.

Disconnect the battery. You need to do this anyway because the computer needs to re-learn the sensors and adjust the new injectors.
http://xjtalk.com/images/special/jeepinjector1.jpg

Unscrew the gas cap and let it hang. This helps relieve pressure on the fuel system. You really don't want gas shooting every where when you disconnect the fuel line.
http://xjtalk.com/images/special/jeepinjector2.jpg

Remove the tube from the throttle body and stuff a rag or something in there. You don't want anything falling in.
Disconnect the three cables. Two you push forward the throttle cable I used a screwdriver and pushed it to the side until it popped off.
Remove the 3 bolts that hold the bracket to the intake. This bracket holds the 3 cables in place. The bolts are 10mm. Righty tighty, lefty loosey!
Move the bracket and cables to the front of the engine bay and clear of the fuel rail.
http://xjtalk.com/images/special/jeepinjector3.jpg

Label the injector lines! I used a label maker to print 1 through 6 labels.
Now disconnect the EV1 connectors from the OEM injectors.
http://xjtalk.com/images/special/jeepinjector4.jpg

Locate the fuel rail pressure relief valve, yes it looks like a bicycle tire stem. Remove the cap.
http://xjtalk.com/images/special/jeepinjector5.jpg

Place a rag/towel under the stem and use something to press in the pin and let out the fuel. I had to do this for about 30 seconds. Then I stopped, waited about 5 seconds and did it again, and I noticed some pressure had built back up. I kept doing this until I got sick of it. I never could get it to stop "burping" each time I would press in the stem valve.
http://xjtalk.com/images/special/jeepinjector6.jpg

You'll need one of these quick release tools. They are plastic and are pretty cheap (as I recall). I used the smallest one 5/16, light blue on the fuel line.
http://xjtalk.com/images/special/jeepinjector7.jpg

I pushed the fuel line towards the fuel rail and the little quick release tool, then I move the fuel line back and it disconnected. First try!
http://xjtalk.com/images/special/jeepinjector8.jpg

Once the fuel line was off I used the same 10mm socket to remove the 4 bolts that hold the fuel rail to the intake manifold. The 4th, closest to the firewall is a double ended bolt. You're CPS connector is attached to this bolt via a nut and a bracket. You'll be removing the nut, the bracket then the rest of the bolt.

Now the fuel rail is free from the intake. Carefully pull back on the fuel rail. I tried to keep things straight. I didn't want to twist anything. Let me tell you those injectors were really in there. The first one finally came free then the rest. I have a 1" transfer case drop on my rig, and this may be why there was still fuel in the rail. It was at the back of the rail near the number 6 injector. There is a fair amount of fuel in there! You'll need to drain that out. It will come out all it's own if you're not careful when you remove the injectors from the rail!

I took the fuel rail to my workbench and then remove the clips holding the OEM injectors to the fuel rail. I then removed all the old injectors.

One "O" ring stayed in the intake and a few "O" rings stayed in the fuel rail.
Carefully remove them. I then put the lose "O" rings back on the injectors.

Using some left over motor oil I coated the NEW "O" rings on the NEW(ish) injectors. First I placed the new injectors into the fuel rail. The slid in very easily. I was concerned about this so I took an old injector, put oil on it's "O" ring and it slid in just as easy. I was happy that everything was fitting as it should. I removed the old injector and continued installing the remaining 5 injectors.

Once they were in place I installed the OEM clips that I had removed earlier from the injectors and the fuel rail. They fit like a glove.

The assembly of the fuel rail with injectors is now complete.

I used some more motor oil to coat the "O" rings that would be inserted into the intake.

I then placed the fuel rail / injectors carefully lining up the injectors ends with the holes they were to go into, in the intake.

I pushed them in gently. I really didn't think they were in until I tried pulling back on the fuel rail slightly. It really feels lose as the whole thing can pivot up and down easily. I saw that the fuel rail brackets were even with the bolt holes on the intake. This clued me that the injectors were fully inserted.

I put the 4 10 mm bolts back in and tighten them down. Remember the bolt at the rear is the one you use to attach the CPS connector bracket.

Now take the fuel line and reattach it to the fuel rail. Put the retaining clip back in place.

I placed each adapter on each injector then using the labels that I had placed on the injector connectors previously I reattached each connector to an injector.

Then I took the bracket that holds the 3 control cables and used the 3 10 mm bolts to secure it to the top of the intake. There was a clearance issue between the number 3 injector and the bottom of the bracket. This is due to the adapter. I was able to turn the injector to the side slightly.

http://xjtalk.com/images/special/jeepinjector12.jpg

This made it hard to get the bolt in and tighten it. It was a minor issue I just had to use a small wrench instead of my 3/8 socket drive.

Now reattach the control cables to the throttle body, and pop the cables back into the plastic guides on top of the valve cover.

Remove the rag from the throttle body and reattach the tube running to the air cleaner.

Reattach the negative battery cable to the battery.

Return the gas cap to it's normal position in the gas refueling tube.

At this point I double checked everything. Looking for any tools, or things that were not connected.

I went to the cockpit and inserted the key. I moved the key to "run" and quickly went back to the engine bay to check for any leaks.

Nothing that I could see or smell. I continued to check for at least a minute.

Once satisfied, at least for now, I decided to crank the engine. It took a little longer to start, but it started. It was running a little ruff at first, that that cleared up after about 2 minutes.

I continued to check for any fuel leaks. None were found so I took her for a test drive. In the 2, maybe 3 miles that I drove I didn't notice any change in performance. It does run good. I will go to the gas station and fill up tomorrow so I can get a good full tank mpg measurement with the new injectors.

Here is the finished product.
http://xjtalk.com/images/special/jeepinjector9.jpg

This gives you a comparison between the Ford (left) injector and the Jeep OEM injector (right)
http://xjtalk.com/images/special/jeepinjector10.jpg

Here is the single hole business end of the Jeep OEM injector.
http://xjtalk.com/images/special/jeepinjector11.jpg

This is the 6 holed Ford injector.
http://lh3.ggpht.com/_b0ViaGso2Ko/S8EZgn7vVQI/AAAAAAAAABI/Hf95PqNtu0o/2010-04-10%2019.35.31.jpg

[rguignard]

good rightup muddy and the blue gives your jeep some color :poke: jk i know you wish they were red :smiley-laughing021: good job let us know how they work out for you ....gas milage and hows it run and all that :thumbsup:

[Mudderoy]

YouTube- Jeep acceleration test after injector install

[W.O.R.P.Offroad]

so have you noticed any diff?

[Mudderoy]

so have you noticed any diff?

Nope. They're a pretty purple though!

[Ruinator]

As usual great write up!

Curious, why didn't you reset the ECU? I thought just unplugging the battery does not put it in "relearn mode". Maybe I'm wrong

This is the process I always use (as per jeep forum):

This very simple procedure will Erase the “Adaptive Memory” stored inside the PCM and allow a new “Adaptive Memory” to be developed.

After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics.

Please perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn Mode adaptive mode.

Disconnect the POSITIVE battery Terminal and touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.

Reconnect the Battery Cable
Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”


The PCM Adaptive memory has now been flashed, or erased from the PCM.

When you start the engine it will be running off a set of pre-programmed tables that come with the PCM from the factory.

When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”.

The PCM will collect data for Adaptive Memory for the first 50 Warm-up Cycles.

[Mudderoy]

As usual great write up!

Curious, why didn't you reset the ECU? I thought just unplugging the battery does not put it in "relearn mode". Maybe I'm wrong

This is the process I always use (as per jeep forum):

This very simple procedure will Erase the “Adaptive Memory” stored inside the PCM and allow a new “Adaptive Memory” to be developed.

After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics.

Please perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn Mode adaptive mode.

Disconnect the POSITIVE battery Terminal and touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.

Reconnect the Battery Cable
Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”


The PCM Adaptive memory has now been flashed, or erased from the PCM.

When you start the engine it will be running off a set of pre-programmed tables that come with the PCM from the factory.

When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”.

The PCM will collect data for Adaptive Memory for the first 50 Warm-up Cycles.

I have never heard/read of this before. Thanks! No I thought that with the battery disconnected for 30+ minutes reset the ECM.

[96xj]

As usual great write up!

Curious, why didn't you reset the ECU? I thought just unplugging the battery does not put it in "relearn mode". Maybe I'm wrong

This is the process I always use (as per jeep forum):

This very simple procedure will Erase the “Adaptive Memory” stored inside the PCM and allow a new “Adaptive Memory” to be developed.

After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics.

Please perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn Mode adaptive mode.

Disconnect the POSITIVE battery Terminal and touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.

Reconnect the Battery Cable
Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”


The PCM Adaptive memory has now been flashed, or erased from the PCM.

When you start the engine it will be running off a set of pre-programmed tables that come with the PCM from the factory.

When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”.

The PCM will collect data for Adaptive Memory for the first 50 Warm-up Cycles.

where dose this info come from ? :confused:

[W.O.R.P.Offroad]

where dose this info come from ? :confused:

x2 i have never heard this either.

[Ruinator]

I have seen that on NAXJA, as well as Jeepforum.

IMHO, this is common knowlege within those forums. The above is pasted from a self proclaimed Jeep factory mechanic, I copied a while ago from. I think this is why so many people mods (bored TB, bigger injectors, new intake or exhaust) are done without noticable difference. Without draining the memory, the CPU slowly relearns and adjusts to the changes. My .02$

(donning nomex) ok flame away:smiley-whacky119:

[Mudderoy]

I have seen that on NAXJA, as well as Jeepforum.

IMHO, this is common knowlege within those forums. The above is pasted from a self proclaimed Jeep factory mechanic, I copied a while ago from. I think this is why so many people mods (bored TB, bigger injectors, new intake or exhaust) are done without noticable difference. Without draining the memory, the CPU slowly relearns and adjusts to the changes. My .02$

(donning nomex) ok flame away:smiley-whacky119:

I don't think anyone was doubting the information. I know I wasn't. That's one of the reasons I like forums so much. You learn more, at least you do on a free and open minded forum. :thumbsup:

[W.O.R.P.Offroad]

i wasnt doubtin anyone either. but i dont see how the head lights do anything they aint even in the wiring with everything else(like through the ecu). unless its somethin specific with the obd2 models im not sure there.


i do know with alot of the forums out there not only jeep some guy(or girl) will post somethin not knowin anything at all and alot of people will take things in stone. im not sayin the guy you got it from is wrong or doin this but it is know to happen

[Ruinator]

NO NO, gentleman all that is in jest.

xjtalk is my preferred Cherokee site because the enviroment, the friendliness, and lack of attitude. I am ALWAYS open for critisicism. (apologize for my quirky sense of humor)

That is what I do with my ECM, I hope it works for you guys. You all know better or different I am here to learn!!!

Mike

[Mudderoy]

As usual great write up!

Curious, why didn't you reset the ECU? I thought just unplugging the battery does not put it in "relearn mode". Maybe I'm wrong

This is the process I always use (as per jeep forum):

This very simple procedure will Erase the “Adaptive Memory” stored inside the PCM and allow a new “Adaptive Memory” to be developed.

After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics.

Please perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn Mode adaptive mode.

Disconnect the POSITIVE battery Terminal and touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.

Reconnect the Battery Cable
Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”


The PCM Adaptive memory has now been flashed, or erased from the PCM.

When you start the engine it will be running off a set of pre-programmed tables that come with the PCM from the factory.

When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”.

The PCM will collect data for Adaptive Memory for the first 50 Warm-up Cycles.

Ok I did it. We'll see if it works better now. :patriot:

[Mudderoy]

Spoke with a "Mopar god" today at a company outing. He confirmed that this is the correct procedure to clear ECM memory.

[pvt.Tadpol xj]

Morning Muddy. This imfo on the flash is on the Qaudratec site to under the knowledge center title...on left side close to bottom.

[Ruinator]

Mornin Mudd,

resetting make a difference?

[Mudderoy]

Mornin Mudd,

resetting make a difference?

I haven't noticed any yet, but burning a full tank will be the clear indicator.

[Mr Clean]

Found this on Quadratec site:
Home » Quadratec Knowledge Center » Jeep Electronic Control Unit Reset
Jeep Electronic Control Unit Reset

--------------------------------------------------------------------------------
When installing new power or performance accessories how does the computer for the Jeep know that it has a new accessory? Most of the time the computer does not. The computer would need to be reset to take full potential of the performance accessories you have added.

The Electronic Control Module, or ECU as its commonly called, stores the information for your vehicle and your driving habits in its memory. The memory is maintaned by a series of capacitors that hold a charge and maintain power for the ECU when the vehicle is turned off. The following procedure will allow you to reset the memory and allow the computer to 're-learn' how to drive by adjusting to the drivers habits and the vehicles modifications.



1. Disconnect the battery by removing the positive battery cable. Remember, the positive battery cable.

2. Ground the positive cable to the negative cable for 30 seconds to erase the electric charge in the capacitors.

3. Reconnect the positive cable to the battery.

4. Turn the key to on but do not start.

5. Turn the headlights on.

6. Turn the headlights off.

7. Turn the key off.


The ECU has now been reset to its factory settings. For the next 50 warm-up periods the ECU will re-learn the engine and driving habits for your driving conditions and the newly installed parts.

[nomoneysonny]

Are these injector upgrades relevent to OBDI or only OBDII?

[PEI-XJ]

hey Mudderoy did the new ones give better MPG or would u stay with the stock ones

[Mudderoy]

hey Mudderoy did the new ones give better MPG or would u stay with the stock ones

No change :(

[PEI-XJ]

guess i will save my $$$ and might just get new OEM ones

[Mudderoy]

guess i will save my $$$ and might just get new OEM ones

Well my understanding is they are pretty easy to rebuild yourself. You might look into just getting the parts, and take a day or a weekend and refurb them and run them another 150k miles.

I do like that these injectors have more holes though. I think I have an issue that is effecting all the changes that I am making and that's why I'm not seeing a benefit. Once I find the culprit I bet my MPG soars to 50 mpg!!!!

I've had several people tell me to check fuel pressure, so I guess I'm going to have to break down and buy a $30 gauge. If I'm not getting proper fuel flow it could be affecting my mpg, even though it seems to be running great to me, but I only get 11 to 13 mpg city.

[JAG]

I just replaced mine as well, pretty easy to do, but after a couple of weeks doing some research on different forums and stuff, I decided to to with the 703 injectors from some dodge vehicles. same plug as older xj's and they have the four hole tips instead of the Jeeps factory one, and are made to run the same fuel pressure with matched fuel rate. I haven't ran a full tank through them yet but the big differences i could tell immediately were that it will crank up faster now and idle/accelerates alot smoother now, granted i had three OEM's that wouldn't close when i tested before the change. soo IMO not all that expensive or hard to do and it does run better...well worth it.

Great write up though! I really didn't know that the headlights turning on and off were part of the reset. thanks.

[dagr8tim]

Any long term updates? You went with 24 lb/hr injectors? Based on what I've seen, you can get away with a 19 lb/hr injector for 96 - 98.

I've been seriously considering this upgrade for a bit.

[Mudderoy]

Any long term updates? You went with 24 lb/hr injectors? Based on what I've seen, you can get away with a 19 lb/hr injector for 96 - 98.

I've been seriously considering this upgrade for a bit.

Me? None... :(

[Baddmove]

Thanks to this thread and your wonderful pics i was able to remove my fuel rail and rebuild my injectors with the kit from O'rielly's. Cost me 4$ for each injector kit and was pretty easy once i read this thread. I had 3 of my injectors leaking at the top O ring and now all is good..Thanks Mudderoy.

[Mudderoy]

Thanks to this thread and your wonderful pics i was able to remove my fuel rail and rebuild my injectors with the kit from O'rielly's. Cost me 4$ for each injector kit and was pretty easy once i read this thread. I had 3 of my injectors leaking at the top O ring and now all is good..Thanks Mudderoy.

Yep, glad it helped. I know that I can figure stuff out on my own (had to do it so many times) but it really makes a big difference when I can get a good understanding of what I will be doing prior to the job. So that's why I try and take the time to take pictures for write ups.

I always thank others for doing the same, because I know it takes longer to get the job done.

[Baddmove]

1 quick question, i just left the injectors connected when i rebuilt them.. how do you get that connecter (electrical) off the injector, i couldn't figure it out without breaking it?

[Mudderoy]

1 quick question, i just left the injectors connected when i rebuilt them.. how do you get that connecter (electrical) off the injector, i couldn't figure it out without breaking it?

It was so long ago, I don't remember. It must have been pretty easy though, since I figured it out, and I don't remember. ;)

[Baddmove]

It was so long ago, I don't remember. It must have been pretty easy though, since I figured it out, and I don't remember. ;)
there is a metal clip holding them on..lol.. i went out and messed with one cause i was dying to know, hate when i can't figure something out..:bang:

[BLACK XJ]

Thanks for the info, this is a great site.