I have been looking through these forums yesterday and today and reading every thread I can find that seem like they might be relevant to no avail. I have found many threads pertaining to no start conditions but none that seem to exactly fit these symptoms or that have things to check that I have not already checked. So, I am posting a new one in hopes that if this has been covered somebody can point to the thread and if not hopefully it will help somebody else in the future with the same problem. There was one thread with very similar symptoms and the posted indicated that after reseating a relay behind the false firewall on the passenger side of the engine compartment the problem appeard to be solved. I can't find any relays in that area of the engine compartment - there just appears to be what I assume is the A/C evaporator in a box under the plastic cover that has the tool tray located in it.

2002 XJ8, 101k miles

The problem first showed up about a week ago. My Wife started the car and it ran for about a minute then realized she forgot something in the house so she turned it off and came back in about 5 minutes to find that the car wouldn't start. About an hour later I came home to check it out and found the following:

All the dash lights, headlights, etc. come on as normal when switching to the "on" position. When turning the key to the "start" position there is a brief click but no crank. Checked battery power, have 12.4 volts and stays at 12.4 volts during attempted start so it's not the battery. Moved the gear selector from Park to Drive, Neutral, Reverse several times - still no start. I verified that the "click" was coming from the starter solenoid so natural assumption at this point is a bad starter. I don't suspect the neutral safety switch since that would prevent any power from ever getting to the solenoid so it wouldn't click at the solenoid. I picked up a new Bosch starter that day and set out that evening to make the repair - should be a no brainer, right?

After getting the car up on jack stands I decided to go ahead and do some additional diagnostics before actually changing the starter. Checked the voltage at the high current 12v+ connection to the starter - 12.3 volts, had my wife attempt to start the car while measuring - stays at 12.3 volts and the solenoid clicks once. I checked the voltage at the solenoid connection, 0v initially (as it should be), then have my Wife try to start the car again - goes to 12.3 volts for about 1/2 second, the starter solenoid clicks and then the voltage drops back to 0v. I'm thinking... "Hmmmm... That's odd". So I disconnect the solenoid wire from the starter and insulate it to prevent a possible short to ground somewhere and attach a jumper wire to the solenoid connection on the starter and momentarily jump it to the high current wire to the starter motor. Starter cranks over just fine. I repeat this process several times running the starter motor for varying amounts of time from just a quick crank to several seconds of cranking. Works perfect every time.

At this point I reconnect the solenoid wire to the solenoid to continue troubleshooting the problem and low and behold the car starts fine. I wiggle and tug on the wire to the starter solenoid to try and reproduce the problem to no avail - the car starts perfectly over and over.

I decided there wasn't much more I could diagnose since the problem could not be reproduced and she continues to drive the car as normal. After a few days and driving it alot over the holiday weekend with no problems I'm thinking.. "Great, the problem is solved and I'll just never figure out what it was."

Fast forward to yesterday morning, I get a call from my Wife saying the car won't start again. I suggested she could try disconnecting the negative battery terminal just to see if I could help her get it started over the phone. I talked her through disconnecting the negative battery terminal and reconnecting it - still no start. She proceeds to try to start the car a number of times throughout the day and still no start until late afternoon. Then all of the sudden it starts like normal so she let it run for a while and then shut it off. Tried to restart it and it starts fine several times. Unfortunately there was nothing for me to diagnose last night since the car was starting fine - several more times throught the evening.

Fast forward to this morning - the car won't start again, same symtopms, click from the solenoid, no crank. I checked all the fuses in the trunk, pulled all the relays from the fuse box in the trunk and reseated them. Even moved all the relays around to different positions (they are all the same) thinking that maybe then the car will start but some other system will have a problem indicating a faulty relay. No luck, still only a click and no crank. Gently pulled and tugged on wiring harnesses, checked all the grounds I could find, checked the connection block in the spare tire area, all good and still no start.

Finally gave up because I had to get to work.

Any suggestions on what to check next? Is there a direct connection from the key switch to the starter solenoid or are there any electronic devices in the middle that could be faulty? Could this be an ECM problem? I'm kind of at a loss here without having wiring diagrams and a component locator - any help would be greatly appreciated!

Jerry

 

Jerry, intermittent faults are the worst. There is a pdf floating around the forum I think, of wiring diagrams for the XJ.

If you have no joy finding it, I can email you a copy if you p.m. me your email.

 

A wiring diagram would be awesome! When click on your user ID to PM you I just get a page that says I don't have "permission" to view it. Same thing when I click on the "Member List" link at the top.

If you could email to sjaurora@gmail.com that would be perfect!

 

This might help http://www.gusglikas.com/AutoRepairElectrical.htm

 

Take a little time and read this post https://www.jaguarforums.com/forum/s...ad.php?t=41309

 

Thank you for the link to that post - I have read that post, I had actually already found that searching for solutions to the problem. While that problem is similar it's not the same in that my solenoid does actually get power momentarily (for about 1/2 second) when the problem is occurring. After that 1/2 second or so the power to the solenoid drops to 0v so the starter never even gets an opportunity to turn the engine over.

I have downloaded and am looking at the wiring diagrams now from the web link you posted. Thank you very much for that! That is exactly what I needed to be able to troubleshoot further the next time it won't start.

An update to the problem of today - after getting home from work the car started perfectly several times. This is several hours after I couldn't get it started this morning. Unfortunately I have to wait until the car has the problem again to continue diagnosis. The biggest issue is that we are both gun shy to take the car anywhere right now since it *could* leave us stranded and even if it's just one of us and the other can come to the rescue the car would still be left wherever it won't start until it decides to start again. Very frustrating...

From that PDF Manual it seems that the next logical step is to locate the "Starter Relay" and test pin #2 when the problem is present to see if the power at that pin also is only powered for 1/2 second or if the relay is dropping out. Hoping it's just the Starter Relay being intermittent and cutting out just after contact is made. If not then it looks like the problem is either the "Body Processor Module" or one of the various other devices that module depend on to send a start signal to the Starter Relay thus powering the solenoid on the starter.

Again thank you very much for the link to that manual - I'm sure it will prove to be invaluable through our ownership of this car.

One other question I have is that the diagram says that the Engine Control Module is in the engine compartment on the rear passenger side. That is where the Starter Relay is supposed to be and I'll need to check the power there. However, when I removed that plastic cover over that area what I saw appeared to be either the Air Conditioner Evaporator or the Heater Core sealed in a box held together with 4 torx screws. Am I incorrect in thinking there is a heat exchanger of some type in there?

 

Although I am not that familiar with the location of anything on that car I do see two feeds, one to the starter and the other to the engine management fuses and relays. I think the engine management is controlling the solenoid and starter controls and the other goes directly to the starter to power it. You indicated that the other things work in the car but it will not start. If you have power to the solenoid I would be checking the power to the starter http://www.gusglikas.com/images/Auto.../jagxj2002.pdf page 20. Please let us know what you find.

Check the high power protection module; we had a few intermittent no start situations related to it.

 

The starter relay and ignition coil relay are located under the plastic toolbox you mentioned. Take off those four torx(star drive) screws and that will show about five or six relays. I had the same problem and seating those relays helped. Just for kicks, when this happens, pop your hood and wait about 5 minutes and try to re-start. My checks are-battery good, high power protection module in front of spare intact, check battery terminals at that false bulkhead under hood on passenger side.

 

Gus: All that is good, I have good power at the starter, and I get a good solid 12.3 volts at the solenoid when the key is moved to the "start" position too. The problem is that the 12.3 volts at the solenoid only is there for about 1/2 second then drops to 0 volts. Just enough time to kick the starter gear into the flywheel but the voltage drops before it can engage the flywheel and actually turn the engine over.

bigcat01: Thanks for the info about the contents of that box with the torx screws. I'll open that up and continue my diagnosis through the starter relay the next time it happens.

When I find the cure for sure I'll post what it was.

 

I think I am now on track with you. Took a little time to map this out. I hope it helps!

 

May I suggest something?

I've just installed an engine into my 2002 XJR 100, everything was going very well today, got the exhaust on, did a quick check to see everything was nutted up, and connected the battery without the fuel tank loom connected (just done the timing chains and tensioners, so didn't want chains skipping before oil pressure had got behind the upper tensioners).

Anyway, it spun like a goodun, I gave myself a high five and went off to get some gas, came back, filled the fuel tank, clipped the loom back up, and turned the key, it tried and died!
The engine sounded as if it went solid on its first turn, I felt the dread of valves hitting a piston as a chain had skipped over a camshaft sprocket.......socket on crank pulley, engine turned like a goodun???wtf???
It's electrical, I tried again, clicks from the trans? weird, adjusted the gearbox selector cable, tried the key, same thing, click.....P lit up so adjustment correct on that....
checked the starter connections, listened to the relays.....

Everything worked apart from it cranking like it had done not half and hour before....

My fix was this, armed with sandpaper I looked at the heavy cables connecting the fuse boxes together on the right hand side of the engine compartment, unbolted them all, cleaning each face and the posts and bases, nutted them back up, key it and it fired first time. Left it for 10 mins and had a cup of tea, just been out again now clearing the tools away and it works.

Please try looking at these cables, and clean them, it might just sort it.

 

I think we are both on the same track. I provided a oneline of this feed and hope he will post the results when he finds it.

 

I was beginning to wonder if I was the only person with this problem. I have a 2003 XJ8 VDP and reading the original post was if sjaurora was writing a story about my last two days. I sure hope someone comes up with an answer to this. I'll post back if I can figure anything out but I’m very limited in electrical knowledge

 

I've been very perplexed by this problem as I have not found any bad electrical connections, no voltage drop conditions, no loose or intermittent connections. The voltage just goes to 0v at the solenoid after about 1/2 second of full voltage (12.3 volts) when the problem is occurring.

The problem happened again on Thursday morning, exactly same symptoms. Thursday evening it was starting fine again of course - every time I actually have some time to troubleshoot it...

Thursday evening I got into the sealed box in the engine compartment behind the false firewall and everything was clean and all the relays were seated fully. I pulled each relay to check the condition of the terminals, all was clean, no corrosion, everything looked fine. Since that block of relays are all the same part number I went ahead and shifted the position of them all just like I had done to the relay bank in the trunk and put everything back together.

The good news is that the car has started perfectly every time since. Friday morning was fine, all weekend was fine, don't know about this morning yet.

I had read one other post where somebody was having a similar problem and had found a partially unseated relay in that location so maybe it was just some oxidation on one of the low current connections to the starter relay. At any rate I'll post back if the problem occurs again and I'll probably coat all the relay connections with some di-electric grease to ensure a good connection in the future.

It would be great to hear if reseating all those relays solves the problem for anybody else with the same symptoms.

 

I recently received an e-mail with the findings on another car ( 2000 XJ8) with the same problem intermittent start. What he found is that the front left fuse box in the engine compartment, the contacts on the fuse board goes bad. They said that the board will need to be replaced. It is the 5 brown fuses that loose contact. As best I can tell it would be the control module enclosure relays – A/C, Starter, Throttle motor power relay, ignition coil relay, o2 heater and Fuel injection. For RHD it is on the left and on the right for LHD. Now this reinforces other partial information I have been getting. That being loose connections, corroded connections, fuse block broken connections and so on. If I had this problem I would start checking for poor connections from the battery to all the fuse boxes. Use caution to disconnect the battery first.

I hope this helps!

Thank You Tom and Yaisou!

 

Well, my car hasn't started at all the last two days. I got into that fuse box in the engine compartment, switched the relays around and still nothing. I then took apart the power cable connection at the front of the fuse box housing. There are 4 nuts, 2 washers, and the bolt that runs through the housing. I noticed on the outside connection, there was some rust on the nut, washer and cable. On the inside connection there was some minor corrosion on the same components. The corrosion was NOT visible until I took the nut and cable off. I cleaned them up and put on a good coat of battery grease. Thank goodness the cat was alive again!! I'll post back if the fix is temporary.

 

Kudos to you!!!!!!!

 

Yes!

 

My post should be Kudos to all involved and thank you for the success stories and the input. Do we have a consensus that a poor connection on the feed from the battery to the front fuse boxes is one of the problems in the no start?