3278

A few weeks ago, we bought our third Cherokee, which has unfortunately turned out to be a complete heap of ****. Setting aside the broken exhaust, bad NSS, leaking windshield, and 18,000 botched previous-owner repairs - some of which are legendary, and I'll post them later - now it just plain won't start.

Sunday, my daughter and I replaced the exhaust, from the front pipe to the tailpipe, including front pipe, O2 sensor, cat, muffler, and rear pipe. Today, I got in the car, it started fine, I drove a couple miles, came home and let it idle in the driveway for two or three minutes. When I left again, it tried to stall; I gave it a little more gas, and all was well for about 40 feet, at which point it died and wouldn't restart.

The battery was dead at this point - it's not a good one - so I pushed it into the driveway and tried to jump it. It cranks, but never starts to "catch," not even a little. I can smell a little gas when I try, so my thinking is that it's spark that I'm missing.

I'll run that down, but first, one other weird thing: the whole time it sits there, while I'm not trying to start it, I can hear a periodic tick/tock. It sounds like a relay opening and closing, but it sounds like it's coming from the center of the head cover, where I don't see any relays.

Thoughts?

3278

It's not throwing any CE codes.

I just disconnected the battery, and the tick/tock didn't stop. After a while, it goes away, and then comes back if I try to start it, so I have no idea what that could be. Time to go through the standard no-start checklist, I guess.

3278

Ignition fuse was blown, but I replaced it and it still won't start. Searching the forum with this new information.

3278

Things I've ruled out:
O2 sensor wiring isn't melted and shorting.
Gas is flowing to the fuel rail.
I can hear the fuel pump start.

Any ideas on how I can check for spark without someone else's help? By myself today.

3278

Okay, then. 15A Ignition mini-fuse under the dash was also blown. And someone had stuck a 25A mini-fuse in the 20A IOD mini-fuse socket...which was also blown.

This seems bad. If my under-dash Ignition fuse, under-hood Ignition fuse, and under-hood IOD fuse are all blown, what would that indicate to you?

edit: Is it possible that if an O2 sensor were wired incorrectly - I had to build my own harness for the Bosch O2 sensor I used - it would blow these fuses?

RTorrez1

The only thing that I know is if you keep blowing fuses you have a short. You are going to have to track that down or you may not get her going at all. I hate tracking down shorts that can be a major pain.

3278

Replaced the three blown fuses, and it still won't start. Tomorrow, I'll check for spark.

The tick/tock noise is weirder than I'd thought. If I stand by the passenger fender, I can hear three or four different ticks, and they're all in different positions along the engine. They sound like they're coming from some of the spark plugs, but they keep happening even after I've disconnected the battery. Does anyone know what I'm talking about, or what it means?

RTorrez1

Can you post a video or a recording of the sound?

highmileage

MAP?

jake92

You said there is an NSS problem. Did you fix that? An NSS that might of had "issues" might of finally just failed.

Jake.

Bosch o2's are junk. I would find an oem replacement. I used a Bosch o2 with the "DIY" plug in a Honda and it was never right

3278

Mos def. I'll try to do that tomorrow afternoon. I'll also be testing for spark, which should give us some more answers.

That's something I've wondered about. I know sometimes a bad MAP sensor will keep an XJ from starting, and that sometimes disconnecting it will allow a start. I disconnected mine, and still no start. How can I test the sensor?

Yeah, we pulled and cleaned it, and all's been well since then. Won't a bad NSS not even allow a crank?

Yeah, I won't do that again. I pulled the O2 sensor entirely, and still no start. An XJ will start with no O2 sensor, right?

jake92

1.NSS will have a no crank or a no start depending. See if something happens in neutral.
2. You need the O2 is you like any sort of fuel economy.
3. A MAP sensor can cause a no start so can a bad ECTS or the majority of the high authority sensors

3278

Will do! Thanks.

Absolutely! But disconnecting it will still allow a start, correct?

Last time this happened - two XJs ago - it was the CPS, but that threw a code, and this hasn't, which is pretty weird. I have some videos for engine electrical problems and sensors but any direction you can give would be a big help.

jake92

Disconnecting the o2 sensor completely shouldn't affect anything unless the o2 sensor shorted.
Those videos are a good start.

A quick tip on suspecting sensors:
Sensors have a 5V reference, a signal, and a low reference wire. The 5v ref is your power, the signal is the trigger, and the low ref is your ground.Take a voltmeter and back probe the terminal with a paper clip and use the paper clip as your test points. Find your signal and 5v reference (power) and check for your 5v ref. Then test signal to low ref (ground) you should see close to 0v, if these come out correctly then the problem is in the suspected sensor. If the readings are incorrect, suspect faulty wiring or PCM.