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

[Roler]

G’day people, its been a while, hope everyone is keeping well.
Bit of a read, to catch up on the issue at hand:

Xj doesn’t get much action but has been parked for longer times before without issues. Now, for the first time in ages, the Jeep (97 XJ 4.0, auto, 190K km, RHD) doesn’t want to play. Spent two weeks now reading up and testing all kinds of possibilities, and starting to run low on ideas myself.

The issue: Intermittent No crank-No start, which is a pain to try and diagnose

So here a summary of what has been done and checked so far:

• Brand new battery, 650 CCA
• Voltage drop testing batt to starter: (+) side 0.16V and (-) side 0.22 V (a tad high but nothing dramatic) (I jumped 30-78 terminals at starter relay to get it to crank)
• Have 12 V at the starter B- terminal, about 11.5V when cranking


AT THE PDC:

Starter relay clicked, didn’t trust it, bench tested it, energizing pin 85 and grounding pin 86 gives continuity between pin 30 and 78: all ok
For good measure changed it with the fore-sure-working cooling fan relay, still no crank-no start

WITHOUT relay in place:
With key off, have power at terminal (receiving end for) pin 30 and ground at terminal (for) pin 78
With key on, 12.06V at terminal for pin 85 and 0.17V at terminal 86 (!?) (see below, the NSS grounds through this, mine is only 5 years old)

WITH relay in place:
With key on, have 12 volts at terminal 86 (extra wire in the terminal/receiving end ) which tells me the ignition switch is working.
NO change in voltage wiggling the NSS with this. NSS grounds via terminal 86 and with good ground should see 12 V. (there is a good Youtube about that)

At the PDC I can crank the engine when jumping terminal 30 and 78 (with key off) and crank and run the engine when key on and jumping 30 and 78.


Yesterday I took out the key cylinder, ignition switch actuator pin assembly and ignition switch. Actuator pin assembly not broken, ignition switch not damaged/cracked/melted at the connector, connector itself clean and intact, nil corrosion or loose wiring. I couldn’t find info on actually testing the ignition switch itself except a post about measuring continuity over input and output but I could not find that specific post anymore (plus there were about 8 or 10 pins in total on the switch)

Today, took apart the PDC, thinking maybe the pin “sockets” could be loose as was the case with another XJ having similar issues. Pin terminals all solid within their place, no wires damaged or loose



So now, I’m a bit low on ideas for what’s next to check; mechanically everything appears to be able to work, and it can be cranked and started. Just not in the way it should, haha.
I get voltage at pin 86 so everything from key to that point seems to be working as it should, and jumping 30 – 78 cranks and starts the engine so from that point it seems to work too. It screams relay/relay socket….but I have nothing suggesting that in my checkings/measurements!? Also not with other usual culprits. I must be overlooking something

Hope to get some advice /ideas!

Cheers

[LuluBelle]

pin 86 what year? so you are saying every now again nothing? or how frequent is nothing? do the dash lights do anything silly? if you are a early model pin 86 is at the pcm? have you unplugged them all to reseat them? ........................ might be dumb questions but trying to understand

[Roler]

No, late model 97, so the update.

I mean the terminal where pin 86 of the starter relay sits, in. At the PDC.
Dash is working fine, dashlights and everything stay on when turning the key to start. Just nothing wanting to crank or start.

During the past two weeks of testing and reading up, it has occasionallly started normal , only to be silent the next time without anything changed in the meantime

[Classic Boy]

Based on your description of you troubleshooting it screams to me you have a bad contact in the ignition switch.

[Roler]

Originally Posted by Classic Boy

Based on your description of you troubleshooting it screams to me you have a bad contact in the ignition switch.

You'd think so. But then it doesnt make sense that during my no crank, I have power at socket for pin 86. POwer there means everything is working from key to level of PDC..

[alexbrown64]

Hey Roler,

Seems like your pulling your hair out and have tested everything.
To me, it still screams of the NSS. I know its only 5 years old, but just to totally eliminate it being an intermittent problem, why don't you try this 5 minute free mod and run it for a week.

You Tube

If its not that, could it be an intermittent problem in the computer?

Cheers,

[Classic Boy]

There are a number of contacts in the starter switch on modern engine management that do a number of things simultaneously such supply power in the start position one for the starter relay others are to send the start command to the ECU and other modules, having a poor contact on the other contacts can cause a no start.