Intermittent no crank no start...running low on ideas

[alexbrown64]

Originally Posted by Roler

I think I answered my last post;I don't think I feel the relay click when turning key to ON... or significantly weaker than the others in the PDC.

Edit: changed it with a good relay, same not clicking.
Maybe not answered yet..

Tried jumping 30 and 87 again key off crancked and when I tried again, with keyt ON only 10 seconds later.... nothing. Doesn't even do that now anymore, not even with key off. Fuses in PDC still good. I made something not exactly better...

Hey Roler, I just went out to my Jeep. I turned ignition on, with my finger on the start relay, and i can feel it click on and then off. I can't profess to know exactly why they do that (is it a test?). But anyway, i then proceed to turn the key to crank and i can feel the relay click back on and stay on while the car is cranking.

Cheers,

[Roler]

Alex, your measurements make perfect sense. And thats how I would imagine my system working as well.
The reason of me using the positivie batt terminal for some measurements, was to find the ground, since I suspected something not correct with exactly those pins.
There was something not correct from the beginning of attacking this problem. I laso was confused due tp seeing videos that mentioned pin 85 instead of 86 being the pin energized. When I looked into the wires on my relay , it was 86 getting the power wire in, like states above being the correct way.

Both my 86 and 85 getting 11V in ON, where it should not, as you said and measured, makes me feel its acting like its in START instead. ignition switch?

I'll do your measurements tomorrow and report back.

Also ,I am afraid though that I have created another problem on top of the old one; it now doesn't crank anymore when I jump 30 and 87, something which until now always still worked. It did crank, then I wanted to try with key on (thats how it would start up), but instead it completely died when I did that with key on.

Ill go back out to the XJ again tomorrow

Really appreciate your time and effort with this mate, just for that alone I need to find the answers.

Cheers

[awg]

I would disconnect the starter solenoid and attach a test lamp you can see

that gets rid of a great big variable that still is not ruled out

once the relay can be stimulated by external jumpers, including 12V in

that also (largely) proves out wiring

the only other thing I do not understand is the role of the PCM connection which is parallel to the NSS leg on the circuit diagram Alex posted

I think there is an explanation in the FSM somewhere about how that works

[awg]

Originally Posted by Roler

Also ,I am afraid though that I have created another problem on top of the old one; it now doesn't crank anymore when I jump 30 and 87, something which until now always still worked. It did crank, then I wanted to try with key on (thats how it would start up), but instead it completely died when I did that with key on.
Cheers

I would disconnect the starter solenoid wire and attach a test lamp you can clearly see

that gets rid of a great big variable that still is not ruled out

once the relay can be stimulated by external jumpers, including 12V in

that also (largely) proves out wiring

the only other thing I do not understand is the role of the PCM connection which is parallel to the NSS leg on the circuit diagram Alex posted

I think there is an explanation in the FSM somewhere about how that works

[Roler]

Did your measurements this am, see below. My values are in Bold behind your measurements.

Originally Posted by alexbrown64

OK Roler,

I have taken a different approach to you. I dont want to short anything out by testing with leads on the positive battery post.. but this is what i have done so far, so you can test yours..

I looked at your results scratching my head.

So i got my DMM out and got the mighty XJ opened up.

I noticed you said you power at 86 with the ignition on.This is wrong

If you had 12v with ignition on, your car would want to start ,as it would energize the coil in the relay and jumper 30/87 etc..

You only want 12v to 86 when you crank, as that will start the chain of events. Thats the first thing i just tested in mine a few minutes ago....

My own testing…. [ My (Roler) values in bold behind yours from here down]

One probe in pin 86, the other on battery earth. 0.46v when ignition on. (this is what you want for a no start condition). 11.7V its 0v only when key off or turned to accesories

One probe in pin 86, the other on battery earth. Ignition crank… pin 86 goes to 13v. (This is what you want to energize the relay coil). 12.10V

This happens in D, P R etc.. doesn’t matter, as its pin 85 Earth that controls earth in P and N so that car wont start in gear. (remember , i had the DMM earth lead on the car earth battery terminal.)
I also thought to check Pin 85 (eightyfive. It showed 11.7V with key on in P as well as Drive

Set up DMM between 86 and 85. 0.2v with ignition on. (this is correct, as no voltage should be going through while ignition is just on.) 0 (zero)V you said this is correct in yours as " no voltage should be going through which makes perfect sense. But isnt it so that this way of setup, it shows the DIFFERENCE in potential between the 2 points, which could also be meaning 0.2V since its almost the same at 86 and 85 in mine, those 11.7 V at both 86 as well as 85 with key on?

Set up DMM between 86 and 85. 11v while cranking in Park. (This would be about right to activate the relay coil) 0.04V

Set up DMM between 86 and 85. 5v while cranking in Drive. (This would be about right to not activate the coil, and thus Jeep wont start in gear.) 0.04V

Can you run the same tests Roler, as something isn't right with your 85/86 pin setup.

Cheers,

Also:
With key off I have 12.4V at terminal 30 and good ground to terminal 78 (0.4 Ohms), so why it is no longer cranking when I jump these, makes me think it is now also something with the solenoid/starter that causes it no longer to do that (@ awg: how would the setup with testlight be done: disconnect power lead to solenoid termindal, attach testlight/dmm and other end/probe to ground post on battery?).


That's where I'm at this morning

[Roler]

SO, correct me where I'm wrong, but it seems to tell me:

1) Key ON powers 86 with 11+V where it should not, because that should only occur on START; that could almost only be a thing in the ignition switch?

2) I have 11+ V at key ON on pin 85 in P and Drive, which in addition to point at 1) , would mean it gets grounded there in Park but also in Drive , which would mean the NSS?

3) DMM between 86 and 85, you go from key ON 0.2V to 11V on cranking. Mine stays the same at 0.04V.
This is actually similar to a voltage drop setup; which would mean no voltage drop between the two pins. Initially I thought I lost ground turning to cranking, but thats not the case, since I have still 11+V on pin 85 (only measuring 85 there, not between 85 and 86) when cranking

But please correct me where wrong!

[Roler]

pm: This is the Youtube I used, its actually explaining all the testing very cleary. NSS at the end

the reason I got confused measuring initially (before I got on here to ask for help) is in this video and wireing diagram PIN 85 GETS THE POWER AND 86 IS THE GROUND!!!! So keep in mind when he talks about 86 its actually my/our 85 and vice versa. Then it makes sense.

Also, he mentions at some stage : "when turning the ignition switch , wer'e getting 12 Volts on the relay pin 86". So you can understand my confusion, plus he didnt state turning to ON or actually cranking..

I'll go and check what my NSS says...

You Tube