How many people seen the movie "Back to the future" ? Remember how the delorian had an issue starting ? On time Marty even smash his head into the steering wheel and magically the car started ? My jag has the sam dam issue ! When I first got my car the car was a complete hit and mis as to if it was going to fire up... then I went and told the guy at a very reputable radio install place to put EVERYTHING back to stock in the trunk . He ripped out all the previous owners CRAP that didn't work, and rewired the harness back to stock. He put in new alpine speakers, and removed all the junk speakers the other owner had... he removed the ground wires the previous owner had attached everywhere and magically the car started starting without issue for a YEAR ... then, a few months back someone rear ended me... I take my car to the body shop to fix the bumper and broken tail light. I get my car back and guess what, the unpredictable start issue is back... my car sat in the garage for a week, and every day I try to start it, the thing would crank but no fire... so today, I remove my golf bag from the trunk... pull down the back seats then lock everything back in place, guess what .... the car starts the first time I turn the key... is there some kind of child safety kill switch tied into this child anchor bolts in the back seat ? How the hell can I get to the bottom of this.. I hate to take the jag out because I'm always afraid I'll get to some remote parking lot and the thing might not start ..

 

It's back to not starting this morning Gets old after a while ..

 

Any codes? Have you measured fuel pressure?

 

Hi there - Just a couple of questions for you if I may.. when you say it doesnt fire up - what DOES happen?

Does the dashboard light up everything as expected?

When you turn the key does it turn over?

In view of you believing that removing and refitting earths in the car, and all OK until you were rear ended it makes me wonder if you have battery or battery earthing issue as both would have been disturbed heavily in the shunt and the work to correct things, but it does all depend on the answers to my first two questions....

 

there is NO codes...

All the dash lights ALWAYS come on regardless of if the it fires up or not..

The starter always engages at the turn of the key, the only thing that is different is sometimes as soon as the starter kicks in the things starts...

or

The starter just cranks and cranks with no fire. It is completely random..

Some times it will start at the turn of the key, sometimes it don't.. radio and dash lights always work ..

 

If it is cranking fine you are down to either spark, fuel or air issues most likely. Does it smell of fuel when it doesn't fire up?

 

never really a full smell... just crank no fire... it so strange that sometimes it will start RIGHT up without ANY issues... its completely hit and miss..

 

If no smell of fuel or flooding when cranking for longer time that would point towards fuel line.. but there are others here that can help you in much more detail than me,. my knowledge is more old school should I say lol ..

But, I do believe your earthing issue is a bit of a red herring, but saying that I'm not too sure how many fuses in the boot area apply to the engine area - maybe connections under the fusebox there might be dodgy and exasperated by the cabling previously and disturbed by the tail end bang?

Either way, give this a day or two for people to pick up on your thread & I am sure you can be pointed in the exact direction to solve this.

 

is it not strange that if it was a fuel or air or spark issue that it would be so hit and miss on when it happens ? that is what stumps me ...

 

Removing previous owners handy work = work in trunk area
Shunted in rear end = work in trunk area
Opening and closing seats in rear = work in trunk area

I think I'm seeing a pattern here..........................

Fold the rear seats back down, remove the carpet and trims from the trunk area and have a hunt through the cabling that goes each side, see if you can see a splice that might have been missed with the previous owners work.
For audio work they would have had to pick up power and earth's from somewhere. And close to the fuse boxes is ideal for that.

 

Keep in mind codes are primarily generated for emission-related faults. A no-start condition typically doesn't set any codes because it's not an emissions problem. You gotta think like a bureaucrat sometimes when dealing with computers. Normal logic is not part of the equation...

Since everything seems to be related to disturbing the trunk area, what about the relays in the rear power distribution box? Maybe one got bumped and is barely making contact. One is for the fuel pump. I think there are four others that control ignition-switched power to other circuits. Make sure they are firmly seated. Remove the relays one at a time and inspect the contacts for arcing, too.

 

Pull a park plug crank the car and check for spark. Also check for fuel by carefully pressing a screwdriver to fuel rail valve. If spark and fuel are present I would suspect a bad crank sensor. Exact same issue happened to me ironically at the AutoZone parking lot. The local parts store carries it, easy to replace and only costs 40 bucks.

 

curious, would a crank sensor throw a code ?

 

Are you doing the repair?
These cars only work if you can DIY the problems. It will be very expensive for a shop to track this down.

What is the PATS light doing when you attempt to start it?
Do you have the shop manual and wiring diagrams? They are free on this forum.
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I have the manual and if I can do the work I will do it myself. I'm trying to understand where the relays are for the full pumps on the 2005 4.2 .. I want to first try to swap them out with another 2005 I have to see if the problem follows the relays . its my understanding there are two of them in the rear boot electric box. just not sure which ones they are yet . The PATS question was an interesting one. I went and looked just to be sure. It reacted 100% normal when I put the key in and turned it to the ACC position. It recognized the key and then the light went off "all normal" ... For kicks, I went and grabbed a old key I had that I knew didn't work any more in this particular Jag. Put the key in and turned it to the ACC position and the light flashed clearly recognizing that it has the wrong key in it. I would say the PATS is working without issue.

 

Good news: fuses, relays etc are all in the manuals etc.

 

Looking at the manual, it looks like R15 and R8 are my first points of interest.

 

here is something interesting. I removed the R15 relay, dusted the prongs off a little and put it back in and the thing started right up ? red herring ? prior to that, the car had not started for about the past three days of trying it..

 

Is R15 the relay for the fuel pump at all?

 

I think so, looking at the service manual it is listed as ;

R15 FUEL PUMP RELAY

In the rear fuse/relay box..