Oh what fun. So this started a year ago.Right around when I drove from Los Angeles to Savannah. A glorious trip that I wrote about and posted here. Then I drove it 2300 miles up to Gettysburg, Dayton, Auburn, Indianapolis, Bloomington and Franklin, TN. Then up to New York State, Washington, D.C, and back to Savannah for another 2000 miles or so. The car was a delight and supremely comfortable and reliable. Then I put it into dry dock while I finished the leather seat project. Now it has this chronic no start issue and it just sits in the driveway jealous of the Lexus...

My XJ8 just doesn't start sometimes. Now, I have read every thread about this issue as many of us have suffered with it or or suffering now. Sometimes The car starts just fine. I can turn it off and it will start up again. Then-confident that all is well I will load it with my day's stuff and get in and--no start. Just nothing. The seats readjust and I can hear the fuel pump whirring but nothing at the starter. I had the starter, alternator and battery checked. I put in a new battery thinking that might be the issue but no... I removed my ELM 327 OBDII thinking that was slowly draining my battery (and it kind of was). But still this issue persisted. I can go outside every morning to start the car and it starts right up. But if you turn it off and try again sometimes it starts and sometimes a Transmission Fault appears or the airbag light stays on or the check engine light comes on. Or I get a camshaft or crankshaft position code. And then I will try it one more time and it starts up fine and nothing appears in the window of doom.

I have replaced my security module and my body processor module. I have bought an exciter ring to install but haven't yet because if that is not working then why does it sometimes start up just fine? I have tried using my other key thinking the key transponder went bad but that isn't it either. My lovely Jaguar -Lord Donnington- is now as reliable as my Ronson lighter...I just can't trust that it will start. I carry a jumper thing in my trunk and sometimes that will get the car to start but it is random and even that doesn't always work. The battery has 12.45-12.74 volts at rest and over 13 when running. So I just don't know where to look next. I checked the ground strap near the front of the car and next to the battery and the firewall connector under the plastic cover and those are all tight and not corroded. So,,,

What next? Any suggestions? Thanks.

other than that the engine is strong and the car runs beautifully. When it can get started that is.

Scott
Savannah, GA

 

have a look at the terminal at the box where ecu lives, it may be rubbished and then you get intermittent no start.

 

Thank you for the fast reply. I did check that terminal under the false bulkhead and it looked great with no corrosion and on tight. What else might it be...?

 

will it start after key removal reinsert or lock unlock the car?

 

That doesn't seem to work for me. I know some have had success with removing the key and reinserting it to get it to start. But using that technique doesn't seem to start the car.

 

ok those two were easy shots next i would make sure that correct voltage is present at the starter motor and clutch test all ground points and positive lines
your battery voltage looks ok but those intermittent codes in bunch usually appear at low battery, maybe next time it occur hang it to lexus, or just have batt tested,
i don't propose hard reset cause i think it is overrated but you may try if you wish.
If all above is intact than my wild guess would be that it is security related issue, but it is just bet

 

So the problem is the starter not rotating , correct ?

In replacing the SLCU and the BPM requires the software # on the items to match that under the bonnet as the master label ( by the windshield )

I can be incorrect on these items

To split the starter problem in half the starter solenoid relay must click by feel every time

You can use a test light between socket 1 and 2 of the relay

There is a common issue terminal post under the bonnet referred to as the false bulkhead



See page 51

X300 01/E COVER (jagrepair.com)

Your starting system can be though of as this

The BPM must get agreements on the left side so the BPM can provide a ground on the right side to close the starter solenoid relay

 

Pull your starter and inspect the contactor. I had an issue for a while where the car would randomly not start for no reason, try a bunch of times and eventually it would fire right up. Very intermittent, sometimes would happen a dozen times in a row, sometimes wouldn't happen for a week.

Eventually it started to start but really struggle when turning over, like a dead battery... replaced the battery as it was aging anyway, that didn't fix it. Took the starter out, found that 95% of the copper terminal thickness was gone from where the contractor slams into it. Put in a reman starter, don't think I've had the issue since.
I bet I even have photos if I dig hard enough...

 

Thanks, Parker. I will check the starter relay. But sometimes it starts perfectly normal. So everything is communicating and working properly. It's the weirdest thing...

 

Thanks. That makes sense as it is so intermittent. In the morning I can start it, turn it off and start it again no problem. On the third attempt to start it I will get a low crank and then it catches. Weird codes come up. I turn it off and try it again and nothing. No click-nothing. I will go out tomorrow morning and it will fire right up. So strange. I wonder why it works sometimes but not always.

 

something electrical getting poor contact from time to time due to termal expansion / contraction or car use like vibration or wind.

 

The low crank would indicate you have the agreements to start, .just no umf

So the next step is battery connections , starter relay swap , may have a bad pulling / control coil or power contacts both inside

Don't over tighten the battery post but do inspect the battery protection module nearby as there is a history from reading on the terminal nuts comming loose

If it is the starter motor giving out the relay will click every time anyway as normal

You have the ECM ( engine ) relay that will be clicking before the start key rotation position

The rest of the car should come electrically alive before the final key rotation position

If the rest of the car does not not come alive then the ignition switch./ king relays but need to focus on starter behavior

The king relays distribute power around the car

These are the 3 circled in red