2008 3.8L Injector resistance variance

P

plext0r

New member
Hello all,
This forum has been a tremendous asset to my son and I as we learn how to maintain his 2008 JKU. He has been experiencing P0202 and P0302 for a couple of weeks. We did a bunch of research and tried replacing the spark plug on cylinder two. We reset the codes but it came back four days later. After further research it appears we need to focus on the injectors. This is our first time taking off the intake manifold, etc. We read the resistance of each injector and would like to know if the variance shown below is enough to show injector #2 is truly bad.

  1. 11.7
  2. 15
  3. 11.8
  4. 11.7
  5. 11.8
  6. 11.9

Thank you for your assistance.
 
WJCO

WJCO

Meme King
Do you happen to know the specs? My gut feeling would be that it is bad being the other 5 are very close to each other whereas the #2 cylinder is not.
 
Judesign

Judesign

Caught the Bug
Sucks that info like this can be so hard to find without an expensive subscription to a service like alldata. I'd be interested to see if the misfire followed by swapping injectors but that would take too much work on this engine.
One thing that helped me was looking up information on Chrysler town and country minivans lol. Same engine and it seems there is more out there on the web about repairing these than if you look up JEEP.
Out of curiosity what led you to fuel injector vs ignition coil or wire etc?

Edit - from what little I can find it seems that resistance variance is 10-16 ohms but the logic is if one is completely different than the others, and coordinates with the misfire in that cylinder , then replace that injector.
 
Last edited:
P

plext0r

New member
WJCO said:
Do you happen to know the specs? My gut feeling would be that it is bad being the other 5 are very close to each other whereas the #2 cylinder is not.
Click to expand...

I found a table for resistance based on engine temperature:

  • –20° C (–4° F) 10 ohms (+/– .6 of an ohm)
  • 20° C (68° F) 12 ohms (+/– .6 of an ohm)
  • 60° C (140° F) 14 ohms (+/– .6 of an ohm)
  • 100° C (212° F) 16 ohms (+/– .6 of an ohm)

Since the engine is cold and 5 of the injectors measure ~12 ohms and one is out of spec, it appears I need to replace the injector. Would you agree?
 
P

plext0r

New member
Judesign said:
Sucks that info like this can be so hard to find without an expensive subscription to a service like alldata. I'd be interested to see if the misfire followed by swapping injectors but that would take too much work on this engine.
One thing that helped me was looking up information on Chrysler town and country minivans lol. Same engine and it seems there is more out there on the web about repairing these than if you look up JEEP.
Out of curiosity what led you to fuel injector vs ignition coil or wire etc?

Edit - from what little I can find it seems that resistance variance is 10-16 ohms but the logic is if one is completely different than the others, and coordinates with the misfire in that cylinder , then replace that injector.
Click to expand...

Thanks for the info; I also saw the Chrysler / Dodge 3.8 is the same engine but I hadn't actually searched for it much. I also found the table I just listed above.
 
WJCO

WJCO

Meme King
plext0r said:
I found a table for resistance based on engine temperature:

  • –20° C (–4° F) 10 ohms (+/– .6 of an ohm)
  • 20° C (68° F) 12 ohms (+/– .6 of an ohm)
  • 60° C (140° F) 14 ohms (+/– .6 of an ohm)
  • 100° C (212° F) 16 ohms (+/– .6 of an ohm)

Since the engine is cold and 5 of the injectors measure ~12 ohms and one is out of spec, it appears I need to replace the injector. Would you agree?
Click to expand...

I would replace the one injector if I were in your position. However, if you move the whole rail and disturb the other injectors, I would strongly recommend replacing ALL orings, even for the other ones. A lot of times, those old orings will leak fuel once moved.
 
P

plext0r

New member
WJCO said:
I would replace the one injector if I were in your position. However, if you move the whole rail and disturb the other injectors, I would strongly recommend replacing ALL orings, even for the other ones. A lot of times, those old orings will leak fuel once moved.
Click to expand...

Thanks for the advice, WJCO! I'll do that.
 
P

plext0r

New member
FYI, when we removed the air intake plenum or upper manifold, we noticed oil leaks around the valve covers. We decided to go ahead and replace those gaskets as well. In the end we ended up replacing all six spark plugs, the valve cover gaskets and the cylinder 2 injector. This is a lot more than I ever thought I'd do but we got through it. :rock:
 
MattAlpha

MattAlpha

Caught the Bug
Great job getting it done and sharing with the rest of us who are still running a 3.8L.


'07 JKUR ... mod'ing never stops...
 
P

plext0r

New member
ScoobyCarolanNC said:
Nice! That's got to feel good. How's it running?
Click to expand...

So far two days without any codes. My son's taking it back and forth to college. We'll see how it holds up. When I had the plenum off I thought about the intake manifold gasket but since nothing around there is leaking (to my knowledge), I figured it could wait; plus I didn't want to deal with draining the coolant, etc.

It was quite a feeling of accomplishment by both of us. :thumb:
 
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