Engine cranks but won't fire
 

My car is a 2000MY 4.0 Sovereign LWB. Out driving today and the idle revs climbed to about 1200 then when I pulled onto my driveway the revs were going up and down from 1000 to 2000 revs in a regular fast pattern. Switched the engine off, let it settle for a few minutes and then tried to start her up. The engine is cranking OK but not firing at all. Disconnected the battery to re-boot the system but still not firing. The MAF sensor is clean. Any help would be appreciated. Thanks.

Here is the long list to check but the throttle body comes to mind first. Remove/reconnect electrical connectors. No CEL/MIL?

https://www.jaguarforums.com/forum/s...ad.php?t=30792

Just to add....the dash warning comes up 'Engine Safe Mode" when I'm trying to start her up.

Any tach movement while cranking?

No tacho movement. Prior to this grief I was getting the warning 'trac unavailable' with the ignition on but then the warning disappeared when the engine started. Don't know if it's related. Managed to flatten the battery so it's now on charge until Sunday then I'll try to start her again. Luckily I have a few more cars so I'm not having to walk to the pub !!

What was the problem/cause?

Sorry I misread your post and thought you got it started.

Trac fail when cranking
 

Getting the trac fail only when cranking and then having it go away when the engine starts is a dead giveaway of a failing battery. When cranking the voltage drops below the threshold required to properly operate the ABS/trac module and once the engine starts and the alternator is working voltage is fine.

If you cranked until the battery was dead you can be sure it's flooded as well.

Thanks for that 'Real-Tech'. I'll stick the charged battery on tomorrow and see what happens. Fingers crossed.

A flooded 'Nikasil' engine takes a scary starting procedure.

Look under 'Car won't start', step 7 for a discussion here:

https://www.jaguarforums.com/forum/s...ad.php?t=29800

Many an owner have given up and had the car towed to the dealer who only used the extended crank procedure to start the car.

It never rains but it pours !! So I went to install the charged up battery and I can't open the trunk, the locking mechanism seems to be either stuck or broken so basically I'm screwed after trying to open the bloody thing for half an hour I gave up. I'll try again tomorrow with either a crowbar or half an ounce of C4. Don't suppose there is a secret trap door somewhere ??

You might try jumping the battery to one of the under hood B+ connectors and trying the electric lock release. Since the key lock is not often used it often gets gummed up and fails just when you need it.

Well Dinger I felt like that myself at times but you are doing the right thing by walking away for a few moments. As for the C4, let me know if you find any I need it for my in-ground pool!!!!! Check your PM when you get a chance.

Forgive my ignorance but what/where is a B+ connector ?

Just outside of the fuse boxes on each side of the engine are bolts with rubber covers that are the feeds from the rear battery. They are the same as the battery B+.

If I recall on my 95 I can use my key to open the trunk. I think the hole for it was in the xj6 emblem on the right. Have you given that a try? At times they can be a little stubborn, if that is the case use a little WD40. Whatever you do, do not force it!

Yes Gus, I tried the key for half an hour plus WD but the lock is completely broken so I will try the B+ underbonnet trick and see if it works otherwise I'm stumped. I assume that I will have to put the positive cable on the B+ underbonnet bolt and also ground the negative. I'll clamp it to my nose.

Yes that is correct. I have a circuit oneline if you send me your e-mail in a PM

Dinger,

You mentioned that your car began reving at idle and you turned it off. You then attempted to restart the car, what was the duration of it sitting idle? I am thinking that you have a problem with you throttle body and could have resulted in the flooding/cylinder wash problem. Before toy get more aggravated with it I would like to ask a few questions. How long was the shutdown before restarting and what other signs or problems have you had with the car in the week prior to this?

TSB 303-58 1999 – 2001 V8 XJ I would like for you to check the connections at the throttle body. This will give you a failsafe warning. No need to change the connectors just get them clean for now. http://www.gusglikas.com/AutoRepTB.htm

TSB 600-03 1998 – 2001 V8 XJ check the breather stub and make sure it is not clogged. I know that it may not be related but do it to humor me.
http://www.gusglikas.com/AutoRepairPlugReplacement.htm

You said that you cleaned the MAFS and that was a good thing. Did you see any excessive oil or residue on it or in the air intake tube?

I was able to find a TSB on my 99 to reflash the ECM for a no start but was unable to access one for yours. I had this done on my car. Need to see if one exists for your year car. ******Found it 303-52 Difficult Or Non-Start to Reflash ECM******

Now if you elect to attempt to restart the car you should add a little oil to each cylinder (check the plugs at this time and replace if necessary) hold the accelerator to the floor and give it a try. I would do it no longer than 30 to 60 seconds. This is to prevent you from burning up your starter. If it begins to start let up on the accelerator and let it run.

Then please give us an update.

Thanks Gus those are great photos on your email link. Managed to open the trunk using the under bonnet bolt trick, re-installed the battery and cranked but no firing. Pulled a couple of plugs and they were dry and with no smell of fuel on them. Called out my breakdown service and after about half an hour of faffing around with his diagnostic computer he came up with fault code P0507 which is the throttle body/sensor/fuel delivery.
I'll start by cleaning and checking the connectors as per your excellent photos and if that doesn't work it looks like a new throttle body may be needed as there is absolutely no fuel delivery and the car won't even fire with nitro squirted into the air intake.
Thanks for everything so far.

No Fuel?

Dinger please go down the list

Check for OBD codes
Check for spark
Check for fuel

In your case before you go deep into the throttle body you should check for fuel pressure going to the throttle body. It is not uncommon to have a failed fuel pump or a clogged fuel filter.