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View Full Version : How to change your Injectors - 1998 Jeep Cherokee - 4.0L



Mudderoy
04-16-2010, 10:10 PM
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.
The adapters were purchased from AmericanMuscle.com. They are "50089 Ford Racing EV1-EV6 Fuel Injector Adapter Kits" and I paid $39.99 with free shipping. Pricey yes, but now I have the ability to run either type of injector without re-wiring.

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
04-17-2010, 06:07 AM
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
04-17-2010, 12:21 PM
YouTube- Jeep acceleration test after injector install

W.O.R.P.Offroad
04-17-2010, 08:11 PM
so have you noticed any diff?

Mudderoy
04-17-2010, 09:04 PM
so have you noticed any diff?

Nope. They're a pretty purple though!

Ruinator
04-18-2010, 12:25 PM
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
04-18-2010, 02:13 PM
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
04-18-2010, 05:07 PM
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
04-18-2010, 05:19 PM
where dose this info come from ? :confused:

x2 i have never heard this either.

Ruinator
04-18-2010, 06:53 PM
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
04-18-2010, 07:13 PM
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
04-18-2010, 07:15 PM
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
04-18-2010, 08:36 PM
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
04-22-2010, 07:45 PM
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
04-25-2010, 05:21 AM
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
04-25-2010, 06:27 AM
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
04-25-2010, 12:31 PM
Mornin Mudd,

resetting make a difference?

Mudderoy
04-25-2010, 12:55 PM
Mornin Mudd,

resetting make a difference?

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

Mr Clean
04-26-2010, 09:58 PM
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.

T- B0NE
07-17-2010, 08:43 AM
Does anybody know if it saves the first 50 or the last 50 warm up periods?
In other words is it always learning or do I need to clear it if I decide to start shifting later or something like that.

jfxj67
07-18-2010, 02:35 AM
I'm not one to play into the flame war, because this is NOT NAXJA or JeepForum! :tongue0013:


Great Write-UP!!!
:thumbsup:

lowrider
08-18-2010, 02:20 PM
what year mustang injectors did you get. i didnt think they would fit in our stock intakes only in the newer rounded one

Mudderoy
08-18-2010, 02:29 PM
what year mustang injectors did you get. i didnt think they would fit in our stock intakes only in the newer rounded one

Seems like they were from a 2009, or 2010 Mustang, but be safe and look the part number up.

lowrider
08-18-2010, 02:46 PM
do you still have the square intake on yours?

Mudderoy
08-18-2010, 03:13 PM
do you still have the square intake on yours?

Yes, sorry, everything is stock on the Engine.

bluedragon436
10-16-2010, 02:19 PM
I want to do the 19# injector upgrade when I swap over to the 99+ intake manifold.... Can't really hurt the gas mileage that's for sure!! Awesome writeup... will be saving this one for sure!!

whocares8310
02-10-2011, 07:50 PM
turning on the lights with battery disconnected...

basically what it does is kill any residual power being stored in the computer.
by turning on the headlights and letting them die then turning them off you drain every last bit of power from your computer and electronics

Niac
02-25-2011, 09:13 PM
Great write up.:patriot:
The injector swaps seem to be ladened with a lot of "Feels faster to me" and "I got 130 miles before my gauge read 1/2 full. It's great cause I only got 128miles before the swap. :stars::stars:
It's good to see someone actually checking his gas milage.:thumbsup:

Mudderoy
02-26-2011, 12:13 AM
Great write up.:patriot:
The injector swaps seem to be ladened with a lot of "Feels faster to me" and "I got 130 miles before my gauge read 1/2 full. It's great cause I only got 128miles before the swap. :stars::stars:
It's good to see someone actually checking his gas milage.:thumbsup:

I was pretty thrilled yesterday, I got 12.97 mpg last tank!

Niac
02-26-2011, 07:24 PM
I was pretty thrilled yesterday, I got 12.97 mpg last tank!

What was your milage before the swap?/

Mudderoy
02-27-2011, 12:08 AM
What was your milage before the swap?/

Same, no change. Nothing I have done has made any difference. That includes adding custom front and rear bumpers.

Well changing the gears from 3.55 to 4.56 helped by about 2 to 3 mpg but nothing else has made a difference for the worse or better.

steph74
03-27-2011, 12:39 PM
looking at your video there Tony ..... RPM ? I have never taken the jeep that fast yet but seriously I have never seen the tach going that high while driving.... IS that normal ?

If I push it in 2nd or 3rd gear it gets to 3k RPM and in 5th gear it will get under 2k unless I am in a mountain road then it is close to 3k in 4th

Just wondering, sometimes I feel that the rpm range should be used a little more like yours and sometimes I feel that it is why I still get 16 mpg in town and 24mpg on highway ;)

Anyway that is a good write up.... too bad it is just for the HO engines lol

Mudderoy
03-27-2011, 10:03 PM
looking at your video there Tony ..... RPM ? I have never taken the jeep that fast yet but seriously I have never seen the tach going that high while driving.... IS that normal ?

If I push it in 2nd or 3rd gear it gets to 3k RPM and in 5th gear it will get under 2k unless I am in a mountain road then it is close to 3k in 4th

Just wondering, sometimes I feel that the rpm range should be used a little more like yours and sometimes I feel that it is why I still get 16 mpg in town and 24mpg on highway ;)

Anyway that is a good write up.... too bad it is just for the HO engines lol

Yeah it's always gone to what ever that max is, 5k? With the 4.56 gears it just get's there a little faster in 1st.

Mad Max
04-19-2012, 08:29 PM
I found this write up and followed it to the letter. Awesome article! It was really helpful!

Mudderoy
04-19-2012, 11:25 PM
I found this write up and followed it to the letter. Awesome article! It was really helpful!

Hey that's great! Glad it was a help to you! :D

Rayburne
01-06-2013, 06:40 PM
Should give better performance with the improved spray pattern.

ALS XJ
04-02-2013, 03:05 PM
I was thinking the same...but heard that 95-97 Dodge Neon injectors work very well...then we come to spark and burn...looking into D.U.I. Screamin' Demon coil, Livewires (spark too hot for stock wires) and some E3 plugs (gapped wide). Anybody running this or similar set-up? BTW...Great write up Tony!