1996 4.0 No Crank, Starter Works When Jumped

[DirtySouthXJ]

Hi,

Suddenly my 96 4.0 automatic would not crank after the last drive (maybe 2-3 weeks after parking it). When I hit the key, I get power at the dash and keyed power accessories work but when I turn the key fully to the start position, I get a single clunk/click and the brake idiot light lights up. I did all the easy stuff like cleaning grounds, battery terminals etc. Doing some searching, I thought maybe it was an NSS issue and tried moving the shifter through many cycles and then starting in both park and nuetral..no go | :

So here is where I am at now..I can start the XJ with it in park and key on by jumping the starter with a screw driver and by removing starter relay and jumping terminals inside the pdc. I'm guessing this eliminates everything else in the system including the starter, power/ground wiring, ignition switch and NSS? I tried swapping a different relay (I believe it was the electric fan relay) and that did not solve the problem, but I'm not sure if that relay is good (the XJ has an aftermarket triple electric fan setup with standalone relay not triggered by the PCM). Is it likely the starter relay that is causing the no crank?

Thank you!

 

[RCP Phx]

You didn't mention charging the battery along with voltage measurements when trying to start? Also you can't eliminate the ign switch since you bypassed it.

 

[Unclewolverine]

I've had two ignition tumblers break on mine, probably ought to check that.

 

[Anak]

Specifically, which grounds have you refreshed?

 

[DirtySouthXJ]

You didn't mention charging the battery along with voltage measurements when trying to start? Also you can't eliminate the ign switch since you bypassed it.

Battery was fully charged out of the vehicle, I'm also having charging problems, which I think may be the voltage regulator in the PCM. I went to work on bypassing the PCM with an external voltage regulator kit when I noticed the no crank issue. I do not know the history of the battery (it came with the vehicle). The battery does crank the engine over without struggle when either jumping the starter posts or relay terminals. So what I did so far eliminates everything but the ignition switch and relay?

I've had two ignition tumblers break on mine, probably ought to check that.

How can I test that? Can I test at the appropriate relay terminal in the PDC (12V at terminals with key in the forward most start position)?

Specifically, which grounds have you refreshed?

Passenger fender, head to firewall, two to passenger side block, negative connections at battery and both battery terminals and posts.

Thank you all!

 

[DirtySouthXJ]

You didn't mention charging the battery along with voltage measurements when trying to start? Also you can't eliminate the ign switch since you bypassed it.

Just to be clear I was trying to start the vehicle to move it before attempting to test charging and install the external voltage regulator.

Wouldn't at least part of the ignition switch have to be good in order to power up the dash, accessories and allow the car to run once the starter/relay was jumped?

I'm not good with electronics lol

 

[Saudade]

When you turn the key to START, what exactly is "clunking/clicking". Have someone turn the key while you listen in the engine bay (hood up). The starter relay is in the PDC. If the relay is clicking but no cranking happens, perhaps the relay is bad. You can temporality swap the relay with one of the others in the PDC (like the fan or AC compressor).

The key (in START) sends power to the coil side of starter relay. The coil then grounds through the NSS. If the circuit completes, the switch side closes and sends power to the solenoid. The solenoid then energizes and pushes out the Bendix to engage with the flexplate and connects the battery cable + to the starter motor.

So Yes, you can probe for 12v at the relay.

The pin layout in the PDC for the starter relay is: (the ... are just to space the pin numbers)

10....9....8
........7
........6

Pin 8 is the 12v from the key
Pin 9 is not connected
Pin 10 goes to the NSS

Pin 6 gets 12v from fuse 3 (40a)
Pin 7 goes to the solenoid.

So Pin 6 should have 12v regardless of key position

Pin 8 should have 12v only with the key in START.

Pin 10 should show ground with the NSS in PARK or NEUTRAL

Pin 7 should show continuity when tested from the relay pin to the small wire at the solenoid.

Could can also test for 12v at the small wire on the starter. Should only have 12v in START.

 

[DirtySouthXJ]

When you turn the key to START, what exactly is "clunking/clicking". Have someone turn the key while you listen in the engine bay (hood up). The starter relay is in the PDC. If the relay is clicking but no cranking happens, perhaps the relay is bad. You can temporality swap the relay with one of the others in the PDC (like the fan or AC compressor).

The key (in START) sends power to the coil side of starter relay. The coil then grounds through the NSS. If the circuit completes, the switch side closes and sends power to the solenoid. The solenoid then energizes and pushes out the Bendix to engage with the flexplate and connects the battery cable + to the starter motor.

So Yes, you can probe for 12v at the relay.

The pin layout in the PDC for the starter relay is: (the ... are just to space the pin numbers)

10....9....8
........7
........6

Pin 8 is the 12v from the key
Pin 9 is not connected
Pin 10 goes to the NSS

Pin 6 gets 12v from fuse 3 (40a)
Pin 7 goes to the solenoid.

So Pin 6 should have 12v regardless of key position

Pin 8 should have 12v only with the key in START.

Pin 10 should show ground with the NSS in PARK or NEUTRAL

Pin 7 should show continuity when tested from the relay pin to the small wire at the solenoid.

Could can also test for 12v at the small wire on the starter. Should only have 12v in START.

Can't tell where the clunk/click is (a single sound, not repetitive like a dying battery), from the drivers seat it sounds like behind the dash.

Looking at that pin information, it sounds like pin 8 might supply power from the ignition switch to the relay in order to close the contact and allow high amp flow to the starter? So if I get 12 v at pin 8 with the key in start position, that should eliminate the ignition switch? If that is the case and I am able to crank/start by jumping either the starter posts and the starter relay terminals inside the PDC, then that would only leave the relay correct?

Thank you!

 

[Unclewolverine]

The tab on the back of the tumbler breaks where it goes into the ignition switch. Depending on how it breaks you can usually turn it to on but won't move the switch far enough to hit the start position. The only way to check is physically remove the tumbler.

 

[DirtySouthXJ]

The tab on the back of the tumbler breaks where it goes into the ignition switch. Depending on how it breaks you can usually turn it to on but won't move the switch far enough to hit the start position. The only way to check is physically remove the tumbler.

Copy, thank you! I'm going to see if I get 12 v "signal" to the relay at the PDC first, if not..I guess I will have to dig into the switch itself..really hoping that is not the case lol!

 

[DirtySouthXJ]

So I finally got some alligator test leads to test pin 8 at the PDC while turning the key (working alone) and I get 12 v effectively. That should eliminate the path from ignition switch to PDC correct? And since I can start the engine from both jumping at the starter and at the relay pins in the PDC, would that not leave the relay itself as the only possibility?

 

[DirtySouthXJ]

@Saudade

^ What do you think brother?

 

[Saudade]

So I finally got some alligator test leads to test pin 8 at the PDC while turning the key (working alone) and I get 12 v effectively. That should eliminate the path from ignition switch to PDC correct? And since I can start the engine from both jumping at the starter and at the relay pins in the PDC, would that not leave the relay itself as the only possibility?

0f I understand this right, then Yes. If you get 12v at Pin 8 when you turn the key to start, the ignition switch works. If you jump the pins at the relay to the starter and the starter cranks, it's not the fuses or the starter.

The Starter relay is the same as others in the PDC. Try swapping it with another in there. If it cranks, then that's the issue. If it doesn't, then you need to trace Pin 10 to ground. Pin 10 grounds through the NSS in Park and Neutral. You can temporarily bypass the NSS using a jumper to determine if it's the issue.

 

[DirtySouthXJ]

@Saudade

First off, thank you for your help!

Yes, I get 12 v effectively at pin 8 when turning the key to start. I can start the engine with key in run (1 position back from actual start) and shifter/NSS in park by jumping either pin 7 to pin 6 at the PDC or by jumping posts at the starter itself (both methods work). I believe I tried another relay in the PDC and it did not start, but when I look at the numbers printed on top of the relays they are different?

Starter relay - 4608650
83159 1785

All other relays in PDC - 4608650
83159 2065

The way I typed the numbers above, is how they are arranged on the relays.

In one of your posts above you said "Pin 10 should show ground with the NSS in PARK or NEUTRAL", how would I test that? Shifter/NSS in park/nuetral, meter set to OHM, one lead to pin 10 the other lead to ground looking for continuity?

Would the engine start when jumped at the PDC (pin 7 to pin 6) even if the NSS was faulty?

Again, thank you for your help it is much appreciated!

 

[Saudade]

If you use a jumper across Pins 6 and 7, yes, the starter should crank (key position doesn't matter). If you really want to start it, put the key to RUN.

Pin 10 grounds through the NSS. You can check for continuity from Pin 10 to any other ground (chassis, engine). You should show continuity with the shifter in PARK or NEUTRAL. If you don't, try shifting back and forth a few times (engine off of course). If you still can't get continuity, you should try bypassing the NSS with as jumper. There are TONS on YT vids and posts on here. If this works, your NSS is bad (easy to clean, again tons of YT vids). You can leave it bypassed temporarily, just be careful to make sure you're in P/N as it will crank in any gear now. If it still doesn't work, you likely have a break in the wire between the relay socket and the NSS connector.

Really any 5 pin relay in the PDC should work. You can use the rad fan relay, ac relay, even the fuel pump (unless you want the engine to run).

 

[DirtySouthXJ]

@Saudade

Copy, thank you brother!

I'll test the NSS grounding as you described. I'm an electrical idiot, but understand what you are saying there, the way you explained it. Yes, I've seen that there are videos on refurbishing the NSS. I may just go ahead and do that regardless, for peace of mind. I'll post my results here once I get this worked out incase it can help someone else. Thank you!

 

[DirtySouthXJ]

Alright..So I installed a jumper from pin 10 at the PDC to ground and reinstalled the starter relay..engine started right up using the key in the ignition. So NSS it is. I'm not exactly sure which connector it is at this time but all (approx 4) in the same "bundle" are soaked with oil, near the valve cover/head close to the firewall. There is also a ground wire in the vicinity that goes to the rear of the block (there's actually 2 or 3 small ground wires there) that has a cheap crimped butt connector in place (obviously not factory). I'm going to clean up the oily connectors and replace the crimped butt connector with a soldered connection and try again, if that doesn't solve the NSS issue (and likely even if it does) I will remove the NSS and refurbish it. Atleast I know the NSS is the problem. Thank you all.

 

[Anak]

Without going back throught the thread, have you played around with the shifter while trying to start the Jeep?

Sometimes you can get it to work just by moving the shifter forward or backward (but still in "Park"). Or it may work if you shift to neutral. Those two methods worked for Varmint #1's XJ until he found the time to pull the NSS and clean it up.

I will also note (for those who live in the frozen tundra) there are low temp grease options. Should not matter in Florida, but the cold temps were a factor for Varmint #1 so I gave him a grease that is designed for the cold.

 

[DirtySouthXJ]

Without going back throught the thread, have you played around with the shifter while trying to start the Jeep?

Sometimes you can get it to work just by moving the shifter forward or backward (but still in "Park"). Or it may work if you shift to neutral. Those two methods worked for Varmint #1's XJ until he found the time to pull the NSS and clean it up.

I will also note (for those who live in the frozen tundra) there are low temp grease options. Should not matter in Florida, but the cold temps were a factor for Varmint #1 so I gave him a grease that is designed for the cold.

Hi Anak,

I tried cycling the shifter many times and tried starting in both nuetral and park, including while pushing the shifter forward without success. Cold weather is not a factor for me, but certainly is something to consider for others in cold climates.

I think I am going to leave the jumper from pin 10 (with relay installed) to ground (passenger fender or battery negative) in place for now, unless there is a reason why I shouldn't? I know that bypassing the NSS will allow starting in gear but I habitually start with foot on brake and shifter in park. I am more worried about fire or electrical damage to components, should I be?

 

[Saudade]

Is the NSS still connected? Do your backup lights work?

Pins B & C on the NSS are the ones that complete the ground when in P/N (This is the Pin 10 on the relay to the NSS circuit). Definitely give all of the connectors a good cleaning especially the contacts inside.

You can test the NSS directly using an ohm meter or 12v test light. With the meter or test light connected to pins B & C on the NSS, you should get continuity (low ohms or lit bulb).