Thetastycat

Hey all - often this thing roars to life almost immediately, but sometimes, like this morning, it does several hard CLUNK CLUNK CLUNK that torque the whole jeep before it finally starts. So far new starter, new fuel filter, new fuel pump, cleaned the throttle body, cleaned the intake manifold, cleaned the IAC. Last night I checked the battery voltage before I started it and it was 12.6 - was almost 14 after starting. This is a head-scratcher; I did replace the negative battery terminal, but I haven't looked at the other end of the negative lead - suppose that would be a good place to look next. Distributor cap/rotor maybe? What am I missing here?

Thetastycat

Here's a video I took today. Funny how I starts right up the first two times and then gets crappy:

I cleaned where the negative terminal bolts to the engine block, but same deal. I ordered a crank position sensor - man, replacing parts is adding up quick! After I ordered it I read you can test the CPS by putting your ohmmeter between two of the terminals - red on the middle one and black on the other you're supposed to test was infinite resistance, but black on the middle one and red on the other was no resistance - not really sure what to make of that.

Any brilliant insights?

Roler

I would clean ALL engine grounds, for troubleshooting.

It looks like you have a pre-97 XJ.
The update cps has 3 terminals, not sure if yours does too. Which ones are you measuring?

Thetastycat

Yeah, sure thing, sorry I forgot to mention earlier - it's a 95, but the PO replaced the motor with another, later 4.0 - not sure what year. I think there was a lead going to the starter on the one I just cleaned, but I didn't pay much attention - I'll do that one for sure. The strap at the very rear looked pretty clean going to the firewall, but no telling what the other end of it looks like that goes to the motor. Are there other grounds besides those two?

Sorry for the terrible explanation of my CPS testing - I got it from the first post on this page: https://www.jeepforum.com/forum/f11/...ensor-1167378/

It's got 3 terminals - it said to test between the middle one and the one closest to the side with the notched cutout in it. When I tested that with my old ohmmeter with red on middle and black on the notched side, I got infinite resistance (the needle didn't budge), but reversing red and black gave me no resistance (pegged the needle). Not sure if that clears anything up or not!

Sure appreciate the help, Roler!

Roler

See above in bold the replies

Roler

Furthermore, in addition to the above and regarding the hard starts (after the first 2 being ok you said)

1) How old is your battery? Also: terminals and connections clean and tight?
It might be the CCA being rather low. Measuring voltage does not say much about CCA, so quick and easy test to get it out of the equation is having it load tested.

2) Do a voltage drop test on positive (power) as well as ground side of the starter system. It provides a lot of valuable information to work with.

Let us know how you go.

Thetastycat

Roler, I can't begin to thank you for all this fantastic info. I'll have plenty to keep me busy tomorrow!! You know, I recall seeing a sticker on the battery from sometime in 2018, and I was always impressed with how strongly the jeep would crank; I never realized the CCA could be different. I do remember XJs tend to have smaller batteries, and the winch I just put in the front bumper calls for a WAY bigger CCA rating than whatever's in there. I think I'll start with that - I'm sure O'Reillys will load test my battery for me and it's just down the road. If it fails, I'll put in the big battery that the winch needs anyway. And if THAT doesn't do it, I'll start hunting down all those grounds. So funny enough the negative battery terminal doesn't go to the fender wall as I've seen on several youtubes - it goes down and connects to a sort of plate on the side of the engine block. So again, who knows what kind of weird 90s hybrid setup I've got going here. But I ought to be able to look around and figure out what's what. Just so I'm clear, what am I looking for? The line from the battery negative goes right to the engine block, but there's a few other things connected to that plate; would I just keep following all the leads that go from there?

Yeah, I'm rocking a SUPER old Micronta multimeter that my dad gave me that SCREAMS 70s if not before - still got the owner's manual in there and everything!! Yeah, the "polarity" swap doesn't make sense to me either - seems like it would have to be a diode setup in order to get different resistance readings. Who knows.

So thanks to you and Google I just learned how to measure voltage drop - that is gonna be SUPER handy.

I've got me a nice long list of good ideas to check tomorrow thanks to you - I'll holler back with the results! Again, I sure do appreciate all your help!

Thetastycat

Ok well today didn't give me quite as much free time as I'd planned, but I did drag the ol Heep to O'Reillys to get the battery load tested, and despite having a sticker from October 2018, and being a cheapo battery according to the O'Reillys guy, it tested over 14v and came back good. He said the alternator was testing fine too.

So I said well hold on, check this out - it'll start fine the first time or two and then get all ridiculous. So I started it TWENTY TIMES for him - and just roared to life every single time........

Still throwing the o2 sensor code, and it'll be here in the next day or two, so I'll throw that in. Crank position sensor will be in later in the week, but I'll wait and see if the problem continues before I throw that in. I did find and clean the oil dipstick ground; I've got a few more to hunt down maybe tomorrow just for good measure - but I'll be happier knowing all the grounds are good and clean.

The saga continues!

Roler

It can not be stated enough how important good grounds are. In any electrical, intermittent or engine running issues.
By cleaning all the grounds, you get that out of the equation and saves a lot of headaches. Plus you're good for some times to come as well with them.
It wouldn't be the first time (and wont be the last) , that cleaning a ground would solve an issue.

Just curious, did you clean the ground before it started 20 times just fine, or after?

Since you still have a code for something, it's always a good idea to continue to address that too.

Might be a good idea to get yourself a digital multimeter as well. You can get them for quite cheap and it will be an invaluable tool to have.

Keep us posted

Thetastycat

Roler, this is serious wisdom. Funny enough it started 20 times just fine before I cleaned the other ground - I wish it had been after as that would have explained it!! NO idea why it suddenly started working fine. Yeah, getting that new o2 sensor in there will help, and I'll track down the rest of those grounds just to be safe - and like you said they're super important anyway.

No telling!! If/when it happens again, I'll holler back....

Roler

yep, intermittent electrical issues are challenging to find.
Even more a reason to go over grounds, electrical connections, sensors.
Spend some time cleaning and checking when you can. It's investing in prevention of some future issues and never a waste of time.

Thetastycat

Ok - so I went after that ground that's a strap from the firewall to the back head cover bolt - MAN that thing is not easy to get to. I can only seem to reach it with an extension and a swivel. AND, the nut is pretty well rounded off - I tried every socket I had that was even close 3 times, and nothing would grab well. I guess maybe I'll have to start taking stuff out just to be able to get to it better - maybe the fuel rail? Ouch.

Anyway - got the o2 sensor replaced without incident, and the check engine light went away immediately. Started fine, drove her a mile or two and the back, started her again, and fine, started again and it wouldn't actually hit, just crank. Tried again and it did the knock-knock-knock. So it was good to replace the o2 sensor but not the ticket yet.

I figure i've got this crank position sensor - might as well throw it in just to see? Why not?

Roler

Did you get to clean all the other grounds ok?

Thats not uncommon, to have to remove other things just to get to the part...thats what takes so much time (plus you will either brake stuff on the way in and out, or discover other things that need addressing haha)
Take you time, the better access you can gain, the more leverage you can have on the bolt. Maybe even visegrips or otherwise a bolt extractor.

The knock-knock, do you mean it just makes a knocking sound, or keeps (normal) cranking?
Not sure if already done, but in that case, a laod test of the battery might be a good idea to evaluate.
Also, make sure your connections on the starter are all cleaned up ands tight (remove your battery connections at the battery if you do this, to prevent getting some sparks)

If the CPS is a good brand sensor, by all means get it in. If it's never been replaced, now might be a good time, since it will fail at some point during its life.
I'll read back when I can find more time.

Thetastycat

Sure thing, Roler - hopefully tomorrow afternoon I'm get time to try to tear enough stuff out to be able to access that nut and really clean up that ground. What little I can see of it looks pretty gross! After I get that one I'm going to hunt down every last ground, whether they look clean or not, and be sure they're good and clean. I've been using a sanding block on them - is that as good a method as any?

So that "knock" is in the video I posted in here a few days ago - it starts to turn over and then kind of goes "clunk-clunk-clunk" before it finally hits. The more I think about it, combined with how weird it is when it does and doesn't start well, makes me think it's just about got to be a grounding issue. I ordered NTK for the o2 sensor and the CPS, so might as well throw it in - like you said, it won't hurt, especially if it's original! 300k miles is a long time.

Thanks again for all your help and patience - I'll get to the bottom of this thanks to you!

Thetastycat

It's amazing what coming back to something with a fresh head will do - 11/16 fits nice and tight! Gonna clean this one up and hunt down as many more as I can. The two near the computer look REAL dirty...