engine wiring harness and missfires

2000 XJ limited. 125k miles.

started missfiring on friday after work, stoped and wiggle checked all injectors. started up and ran fine to get me home. took to autozone to read codes and got a cyl #2 missfire, and injector #2 open circuit. now am thinking either wiring problems or injector problem.

last fall had simmilar problems but on cyl 3, and i dont think i had the open circuit error. replaced injector and ran no problems for approx 8 months now.

took car to dealership today and they are telling me i need a new engine wiring harness becuase the fuel injector leads are heat damaged on cyl 1, 2, 3, 5. cost for harness is $989 plus 5hrs labor (total around $1500). This seems kind of absurd for such a small wiring problem. Anyone have any experiance dealing with this sort of issue? is it possible to just replace the last foot or so of fuel injector wire by very carefully cutting and splicing in some new wire? (solder and heatshrink on each one). Also is it possible to get replacement fuel injector electical connectors or would i have to splice onto the last inch coming out of the connector? Also how about the simple solution? Might i have any luck by simply replacing the fuel injector? It worked last time, right?

please help, dont really have a spare 1500$ lying around.

try the injector replacement again, cheaper, and really nothing to loose.
if that does not work, go ahead and carefully cutting and splicing in some new wire.

Why not get an injector pigtail and replace the defective ones?

Get a cheap digital ohmmeter and a soldering iron and fix the harness yourself. Open up the jacket, find the bad parts and splice in new. Solder the joints and use heat shrink tubing. You can probably buy new injector plugs somewhere or maybe get some from the junkyard, or just go ahead and use the old ones and join at the last inch. If you solder the wires well, you'll be good as new, perhaps better. Make sure especially that you check, and bypass as necessary, any splices that branch to the injectors from the common positive. It's really pretty easy to do. No exotic parts needed. Just wire and a little time. A harness is just a bunch of wires gathered into a common jacket.

With the estimated cost of repair quoted, you really have nothing at all to lose.

thats what i was figuring with the repair, but what is this about being able to get injector pigtails. Is this something that i can buy at a parts store or the dealership? seems to me that having the pigtail would make things much easier.

thewrath said:

thats what i was figuring with the repair, but what is this about being able to get injector pigtails. Is this something that i can buy at a parts store or the dealership? seems to me that having the pigtail would make things much easier.

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I'd try a parts store, just to see what's out there. I wouldn't be surprised if they're available. If not, you might be able to negotiate with a junkyard. If you had two or three inches of good clean wire on each you'd have plenty enough for splicing. I wouldn't plan too far ahead though until you've tested the existing harness. You might not need to replace that much of it.

peeled back insulation around wires and the wire is kinda melted but not completly for the first 4-6 inches or so from the connector. going to take it apart and splice in new wire this weekend. hopefully the damage doesnt go back too far. the mechanic at the dealership did tell me that the connectors are modular and should come appart and i could attach all new wire to the connector. wish me luck.

time to wake this thread back up.

replaced 10 inches of fuel injector wire for cyl #2. connector is modular but doesnt like to go back together and locking mechanism snapped off (too many heat/cooling cycles i guess). took connector apart and plugged little metal plugs right onto the fuel injector pins (no boot, no plastic, no weather proofing). worked great for 1.5 days, then went back to sucking.

now after sitting for 6 days (vacation), it will always miss when cold, and run great when hot. when just driving around i needed to stop and restart the engine to get it to stop missing once it hit full temp. today i sat in the car as it idled from cold to 210. soon as it had is open/closed loop switchover it ran flawlessly. any ideas why this could be?

also, ordered replacement fuel injector from fiveomotorsport.com and some extra connectors (already assembled with pigtails, best $8 each ever). going to replace injector and the maimed connectors on sat, but untill then, anyone got any ideas on this hot/cold missing/not-missing thing? it could be open/closed loop, but could also be injector heating up and getting unstuck or something.

Fuel injector connectors can usually be had at any parts house that carries the HELP! (Motormite) line.

As far as diagnosis, I had trouble with my 1987 years ago which I traced to a "floating ground" for the injectors. ALL SIX OF THEM.

Took some doing, some wire, and some creative re-arranging, but got it sorted. The OEM splices were crimped (OK) and wrapped with duct tape (WTF?)

Re-did them to a single common crimp sleeve, soldered the crimp, wrapped with friction tape, and again with cold-shrink. Never gave me a spot of trouble again...

5-90

how would the engine even run without a ground to any of the fuel injectors, as a remember reading somewhere the injectors are ground switched, so i guess it would be hard to diagnose as they ground would only be present when the injector was firing. also you have any ideas on the hot/cold aspect of my problem?

Not "no ground" - "floating ground." There's a HUGE difference!

With "no ground," you don't have any connection at all. There just isn't a circuit, and you can usually diagnose it fairly easily.

With "floating ground," you have a ground that is a varying potential related to "ZERO Potential" (true ground,) sometimes being NO connection to ground at all, and sometimes being the same potential as supply. Floating grounds are usually a good excuse to stock up on booze - you aren't going to get through this easily. Floating grounds can also be caused by a number of things - cold solder joins, loose crimps, insulation wear, "crosstalk" with supply lines - any of a number of things, and not all of them are obvious.

Took me about 7 hours to figure out what was going on and solve it ("chilled" solder joins form the factory - they were probably good when they left the factory, but repeated heat-cycling had made them "cold." That's why I don't like soldering under the hood - even though average underhood temps are considerably lower than the melting point of solder alloy, you can still get a cold solder - and you've got to be REALLY good to get a solder that lasts "forever." I'm probably that good, I just don't like spending more time QC-ing my work than I did doing it...)

5-90

got out some ---weiser this weekend and went ahead and changed out the injector. dont know why i didnt do it myself last october when #3 went out. super easy, took about an hour. ended up paying abut 50$ to change one out. compare that to 250$ last october at the dealership. 90$ part plus 1.5hrs labor and tax and shop supplies. fiveomotorsport.com is awsome, fast, helpfull and affordable. only thing i noticed is that the factory injectors have a little slot where the retaining clip fits into and the Ford one from 5.0 didnt, so i just put the clip asside and am saving it for later. the fuel rail is held inplace with 4 bolts after all.

also went ahead and cut off the 2 shattered connectors and attached the new connectors i got from 5.0 as well. solder, heatshrink, and friction tape and it looks and runs fantastic.

only thing is that the jeep is running quite hot right now in regular driving (non highway) it will easlily get to the first mark hotter than 210 with ac on and will cool back down with some steady 40mph driving with the ac off to just over the 210. any ideas why it might be running this hot, considering it didnt do that before the injector went out?