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Check those fuel injectors

Jezza

TJ Enthusiast
Supporting Member
Joined
Jan 7, 2021
Messages
574
Location
DFW Texas
Took the Jeep to lunch today. On the way back it lost power and the check engine light came on. I broke out the scanner and it had a code for a misfire on cylinder 3. I checked over the wiring and unplugged the number 3 injector. It had no change when unplugged. I put my noid light on the injector plug and it had pulse. I plugged it back in and used my stethoscope on each injector body. They all had a well defined click except for number 3. I removed the injector off of 3 and found that it had serious cracks in the body. I removed the other 5 and of the 6 there were 4 with cracks in the casing. It appears to me as though they cracked with age or heat and then water got inside and began to corrode the parts inside. I ohmed out the set and number 3 was 3.5 ohms higher in resistance than the other 5. After cleaning up another set I had and installing them it runs smoothly again. A quick drive confirmed the misfire is gone. Long story short, if you have a misfire be sure to inspect those injectors.

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Jezza

Jezza

TJ Enthusiast
Supporting Member
Joined
Jan 7, 2021
Messages
574
Location
DFW Texas
Did you split apart the plastic on the bad injector, was the damage obvious? I don't think anybody here has original injectors without cracks.
No, I didn't. The did look swollen at the cracked areas. I'm assuming there was rust or corrosion under the plastic near the cracks. The set I put on was from an '06 with 30ish k, no cracks :cool:.
 
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Jezza

Jezza

TJ Enthusiast
Supporting Member
Joined
Jan 7, 2021
Messages
574
Location
DFW Texas
When did they change the injector design? I've never had to do do anything with injectors on any of our 4.0's 94, (2)96's 98, 99, 04.
Maybe it isn't as common as I read about or maybe God has just smiled on our Jeeps !
I think they went from the EV1 to the USCAR injector design in 1998-1999. Being Chrysler it's probably not a clean split year. More like 1998 and 7/8ths or something. Could have also been whoever they weren't in bankruptcy court with at the time. I suspect heat and age play a large factor in the failures. This Wrangler has over 220k miles and has lived in Texas and New Mexico.

Also FWIW I was having the long-multiple crank issues with this thing. The fuel pressure gauge would drop from 45 running to 15 key off within about 30 seconds. Overnight fuel pressure would drop to 0. Replacing the injectors fixed that issue as well. The fuel pressure holds overnight and the Jeep no longer has a long or delayed crank time. Starts up perfectly now.
 
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Wtrask

TJ Enthusiast
Joined
Jul 26, 2019
Messages
371
Location
Maine
My injectors all cracked in my 2000. I’m on my 3rd set. First set was just age and rust in the fuel system. 2nd set was the BBQ. 3rd set of rebuilds are going strong!
 

ColoJeep

Just a car guy
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Joined
Jan 30, 2021
Messages
927
Location
Elev.9052'
I think they went from the EV1 to the USCAR injector design in 1998-1999. Being Chrysler it's probably not a clean split year. More like 1998 and 7/8ths or something. Could have also been whoever they weren't in bankruptcy court with at the time. I suspect heat and age play a large factor in the failures. This Wrangler has over 220k miles and has lived in Texas and New Mexico.

Also FWIW I was having the long-multiple crank issues with this thing. The fuel pressure gauge would drop from 45 running to 15 key off within about 30 seconds. Overnight fuel pressure would drop to 0. Replacing the injectors fixed that issue as well. The fuel pressure holds overnight and the Jeep no longer has a long or delayed crank time. Starts up perfectly now.
Thanks Zezza, I had to laugh reading your post. Chrysler / Jeep reminds me of IH Scouts, you almost had to know the minute it was assembled to know what distributor or alternator it had. Prestolite or Delco Remy. I will have to look now at our TJs to see what injectors they have hopefully my 99, (11/98 build ) will have EV1.
 
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Jezza

Jezza

TJ Enthusiast
Supporting Member
Joined
Jan 7, 2021
Messages
574
Location
DFW Texas
I used Injector Rehab after watching their video on them. They were about $90 for a set, I'm sure you can get them from allot of places. My injectors weren't cracked, big surprise.

From what I understand the reason that some injectors are more of a stream rather than a mist has to do with intake and head design. On the 4.0 as well as the Viper the injectors are spaced further from the valves than for instance the Neon where the injector is right at the valves. Also the Neon is a 4 valve engine where the fuel has to be atomized before entering the head to have even distribution. The single intake valve engines rely on the fuel hitting the backside of the valve to atomize. I'm not sure there is really any benefits to be had running the 4 hole injectors on the 4.0.
 
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pagrey

TJ Guru
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Joined
Apr 10, 2018
Messages
7,463
Location
Los Angeles, CA, USA
I'm not sure there is really any benefits to be had running the 4 hole injectors on the 4.0.
Mine could have been worn out and pretty uneven at 150k, no codes or anything. There is a big increase in ease of starting and much smoother overall. I'd say balanced helped with smoothing it out. I've read plenty of other threads where people say it makes it start easy and run smooth and always thought, "meh, no biggie." I was kinda shocked how obvious the change was. It would be interesting to compare it back to back with clean matched stock single holes because it seems like mine were not working great. Hopefully they last as long as my stock injectors did.
 
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Jezza

Jezza

TJ Enthusiast
Supporting Member
Joined
Jan 7, 2021
Messages
574
Location
DFW Texas
Mine could have been worn out and pretty uneven at 150k, no codes or anything. There is a big increase in ease of starting and much smoother overall. I'd say balanced helped with smoothing it out. I've read plenty of other threads where people say it makes it start easy and run smooth and always thought, "meh, no biggie." I was kinda shocked how obvious the change was. It would be interesting to compare it back to back with clean matched stock single holes because it seems like mine were not working great. Hopefully they last as long as my stock injectors did.
I never considered cold start. When the valve is cold I can see that there would be a decrease in atomization.
 

pagrey

TJ Guru
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Apr 10, 2018
Messages
7,463
Location
Los Angeles, CA, USA
I never gave any of it much thought, asked a week ago I'd be on the same page. It is like this guy describes it in this post as far as how the engine runs. I've had the rail out a few times recently wrapping it and checking for leaks, the o-rings are good and the injectors look fine, they still do. I don't really even know how I'd find which ones needed service or replacement other than sending them out. I'm not suggesting anybody run out and do this, just saying it made a noticeable difference in my Jeep.
 

mrblaine

Crew Member
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Nov 20, 2015
Messages
22,998
Location
Quail Valley, CA
I never considered cold start. When the valve is cold I can see that there would be a decrease in atomization.
If someone is looking for any difference between single and 4 hole injectors, there absolutely isn't any in a TJ 4.0. The reason folks report any change is due to taking out 150,000 mile singles and replacing them with new 4 hole. The exact same attributes would show up if they swapped in a new set of single hole.

I've stated this before, I did the swap on a low mile TJ, exactly zero discernible difference between the 20,000 mile single hole and new 4 hole. I did the swap purely to prove what I suspected would be the case and I did it in Kat's daily driver without telling her. I gently monitored the performance via casual questions. How's the mileage? Everything running okay? Then I would drive it from cold to hot and do the cold start, hot starts, spirited driving, etc. and there was never any single thing you could point to that was different good or bad between the two sets.
 
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mrblaine

Crew Member
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Nov 20, 2015
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22,998
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Quail Valley, CA
I never considered cold start. When the valve is cold I can see that there would be a decrease in atomization.
Not that you likely have an issue but I have both sets of injectors. Anyone that wants to learn is welcome to swing by and take the rig for a test drive of any reasonable duration. Bring it back and we'll swap the other set of injectors in and they can go for another test drive. I've got a 100 bucks that says they can't tell me which set is which by how it drives, starts, runs, etc.