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Default How to change your Injectors - 1998 Jeep Cherokee - 4.0L
by Mudderoy 04-16-2010, 10:10 PM



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.


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.


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.



Label the injector lines! I used a label maker to print 1 through 6 labels.
Now disconnect the EV1 connectors from the OEM injectors.



Locate the fuel rail pressure relief valve, yes it looks like a bicycle tire stem. Remove the cap.


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.


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.



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!


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.



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.


This gives you a comparison between the Ford (left) injector and the Jeep OEM injector (right)


Here is the single hole business end of the Jeep OEM injector.


This is the 6 holed Ford injector.
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  #2  
Old 04-17-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

good rightup muddy and the blue gives your jeep some color jk i know you wish they were red good job let us know how they work out for you ....gas milage and hows it run and all that
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Old 04-17-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

[ame="http://www.youtube.com/watch?v=2sOJNsSmWC8"]YouTube- Jeep acceleration test after injector install[/ame]
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Old 04-17-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

so have you noticed any diff?
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Old 04-17-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

Quote:
Originally Posted by W.O.R.P.Offroad View Post
so have you noticed any diff?
Nope. They're a pretty purple though!
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Old 04-18-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

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.
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Old 04-18-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

Quote:
Originally Posted by Ruinator View Post
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.
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Old 04-18-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

Quote:
Originally Posted by Ruinator View Post
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 ?
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Old 04-18-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

Quote:
Originally Posted by 96xj View Post
where dose this info come from ?
x2 i have never heard this either.
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Old 04-18-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

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
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Old 04-18-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

Quote:
Originally Posted by Ruinator View Post
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
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.
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Old 04-18-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

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
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

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
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Old 04-22-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

Quote:
Originally Posted by Ruinator View Post
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.
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Old 04-25-2010
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Default Re: How to change your Injectors - 1998 Jeep Cherokee - 4.0L

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