Help Diagnosing Fuel System Issue

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coleman02

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Hello,
I’m looking for some guidance on diagnosing an issue on my 2002 TJ. The Jeep struggles to start and when it does start it runs very rough. I get huge clouds of thick blue exhaust and it smells like it’s going to explode.
My code reader gives me p0203 code, “Injector Circuit/Open Cylinder 3”. I figured that the number 3 injector was stuck open and dumping fuel into the engine causing the issues.
Now I’ve got the Jeep home finally trying to fix it. I tested the resistance on the injectors, they all seem about the same. I tried putting power via a 9V battery to the injector connections and they all appear to cycle fine.

Not sure what to do now. I figured it would just be changing injector# 3 but now I’m not so sure. Is there a way to check if the injector is receiving the proper electrical input to cycle correctly?
 
If you can pull the injector rail and reinsert the injectors and turn the key on. You should be able to see if an injector is leaking. To see if the injector is getting a signal from the computer use a mood light to see if it flashes when cranking. Here is a kit but verify it has the right one for the Jeep.

https://www.amazon.com/dp/B0002KO4I2/?tag=wranglerorg-20
 
Alright I pulled the rail. With the key on I don’t see any leaks. I can put a 9v battery to the injectors and they all toggle/spray (super dangerous I know).
I’ll see if I can find a mood light to borrow. If that injector is getting power all the time, what would be the first thing to
 
Injector circuit open doesn’t mean it’s stuck open. What the code is telling you is the the #3 injector circuit is open. That means the electrical circuit has an open, otherwise known as a break. It could be a bad connection, a bad injector, or a break in the wire. I’d switch the injector with one of the other cylinders and re-scan. If the code moves to the cylinder you swapped with, you know it’s a bad injector. If the code remains in cylinder 3, it could still be a bad connector, wire, or even the PCM/ECM.
 
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Its the clouds of raw fuel blowing out the exhaust that make me think the injector is open all the time.
If I unplug #3 it still doesn’t start but doesn’t blow super rich exhaust either.
 
If you have a noid light, you can plug it into the harness to see if the PCM is sending the signal. If, not, you can place a stethoscope on the injector and listen for the clicks as it fires. if you don’t have either, you can do as was suggested earlier. Finally, you can have a leaking injector and an open circuit simultaneously. I’ve seen weirder stuff.
 
Well I swapped the 2nd and 3rd injector. Still won’t start, sounds like it isn’t getting any fuel now.
I checked with my code reader again. Now I’m not getting any codes despite the check engine light being on.
I’m lost now. Some kind of intermittent electrical issue. I think I’ll have to break down and send it to a professional.
 
coleman02 said:
Alright I pulled the rail. With the key on I don’t see any leaks. I can put a 9v battery to the injectors and they all toggle/spray (super dangerous I know).
I’ll see if I can find a mood light to borrow. If that injector is getting power all the time, what would be the first thing to
Click to expand...

This is just the sort of redneckery I like to keep in my back pocket for a rainy day. Bravo, sir.
 
Uncle Salty said:
You’ve gone from a hard start and #3 injector open circuit to a no start. is it cranking?
Click to expand...

Yup cranking over good.
I should give some backstory. I started having problems with this Jeep a couple months ago. It was running rough and rich. I was guessing it to be a spark plug issue. The plugs were supposed to have been changed 20,000km ago. I figured it was the coil so I changed it. It ran great for a while then started running rough and rich.
I changed the plugs and it ran great again for a while, then started doing the same
 
Alright little update. I pulled the plugs looking for hints. Cylinder #3 plug is way blacker than the others. I’m back to suspecting that its open way too much.
I’m looking to trace the wires back to the ECM and check for continuity. Can anyone tell me which of these 3 plugs the injector wires go into?

IMG_2466.jpeg
 
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The FSMs are posted on this site in resources.

Most common problem is that back corner on the valve cover when it turns towards the ECU.

Might just have a fouled plug...change the plugs to some recommend Autolite I think 985s... don't quote me on that... before you go too nuts. Or at least check for spark. (Without the injectors out and spraying=)

-Mac
 
macleanflood said:
The FSMs are posted on this site in resources.

Most common problem is that back corner on the valve cover when it turns towards the ECU.

Might just have a fouled plug...change the plugs to some recommend Autolite I think 985s... don't quote me on that... before you go too nuts. Or at least check for spark. (Without the injectors out and spraying=)

-Mac
Click to expand...

Hi Mac. Thanks I’ll check out the resource section.
The plugs are new, I changed them very recently.
Are you talking about the section of wires covered by the plastic box with the clips on it?
 
Also worth mentioning is that this Jeep had hit a deer hard on the passenger side. I’d replaced the fender and grill assembly afterwards. The battery was nearly pushed into the ECM. Wouldn’t surprise me if damage had occurred to either wiring or the ECM itself
 
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Well I found the problem. Ended up being an intermittent short in the fuel pump. Totally frustrating because I checked for fuel pressure multiple times and always had lots. Turns out slamming the back door would sometimes make the pump run.
I have the tank off now. I broke a couple of evap fittings in the process.
Does anyone know how critical the evap system is? I’m not worried about it throwing codes or meeting emissions, this is a farm Jeep. I need a vent for sure, somewhere water can’t get in. Anyone familiar with removing the evap stuff?
 
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