1996 jaguar x300 xj6 w/4.0


Ok so it all began when a close friend of mine acquired a clean title x300 xj6 with the 4.0 from a buddy of his for the low low price of free, the cause being a pissed off home owners association or something like that. Being that he didn't need the car for transportation it just kinda sat other than the few occasions id take it out to run some errands when I was feeling froggy. It never gave me any issues, ran awesome, started Everytime, drove straight, all the buttons and electronics and whatnot seemed to work including the sunroof and cruise control, really was a solid car. Until..... One day he was suckered into lending it out to a local blonde hair blue eyed hottie that needed a vehicle (they'll get you Everytime) and I didn't see it for a couple weeks until somebody showed up to his place saying "hey you are gonna want to go get your jag from the blonde hair blue eyed hottie because she has the hood up on the jag with some sketchy people messing with it. So it was retrieved at that moment. Had to tow it home because it had a no crank issue. later diagnosed it as the starter but around this time I ended up buying the xj6 from my buddy with the idea I was gonna be able to throw a starter in it and be good but unfortunately that wasn't the case. I get the starter in which was easily top 3 most pain in the *** starters I've done and now it cranks like hell but isn't firing up. As far as I can tell it's getting fuel, I cracked the fuel line with the key on and got a reassuring amount of fuel out of it, though no accurate fuel pressure reading or anything, tested spark at the coils and it's got that. I tried using starting fluid and got nothing out of it. Though when cranking in will back fire out the intake sometimes. So I pull the plugs to borescope the cylinders and it visually looked like the valves may have had contact with the pistons, dark colored piston with a faint light silver half circle mark on every single piston. Yet good old Google is telling me these are non interference motors so that really messes with me. I drained the oil because it was obviously over filled and there was 8 courts in the motor as well. And while I had one plug out to check spark I turned the motor over which caused the cylinder with the missing plug to shoot a flame out of the sparkplug hole and so that really messes with me. I'm hoping it's something I can get taken care of without having to spend a bunch of money. Figure it's timing related but idk how that big of a timing issue would be caused. The chain was fine it seemed not a ton of slack or anything.
Anyways.. if you have any ideas please let me know and i know I'm missing somethings so I'll add those as I remember.
Thank you,!

 

Stand by , I'll be on station and operationally ready after wake up

The cylinders are an interference engine and they have a shallop on the piston tops for the valve to depress into

The there are 2 power sourse for the ECU as it must be fully powered to carry on fwd since you have starter rotation

The fuel pump will come on for 3 seconds only in starting and will come on again once the CKPS sees engine rotation , so you will have 3 clicks of the fuel pump relay , On - Off - on

 

The timing chains are very robust on this engine , so odds are no issue

The second power to the engine ECU is the large # 5 right ECU controlled relay , place you finger on it and feel for click closed , this second power is controlled by the ECU and brings power back into ECU , 1 / 2 your sensors , and power " sitting " on the injectors

You would have to use finger feel as other relays will click by sound at same time

Pics coming

There is a crash / inertia switch that can be fickle and give you a spot of stumble under your bonnet , but if you have fuel says good but easy check to cover base



Follow the red lines

 

Does the car have the Check Engine light on? Any codes?

If you had an OBD2 reader, you could check what the ECU is seeing. In your instance, I would like to know what the ECU sees for TPS Opening Percentage. Car doesn't need to be running to read that.

You've checked for fuel, now we should confirm you are getting spark.

 

If the ECU sees the throttle as wide open but the Maas Air Flow as Zero the ECU knows by design not to give fuel at the injectors

The throttle position sensor will never read 0 % open as fully closed but only get down to 13 %

To read this with a common meter the fully closed TPS reads around 0.60 volts DC on the middle Green / Yellow wire ( position 2 in the pic above ) at the TPS connector as it has to be still installed

This is on the Jaguar 801s doc and someone brought up about way back

 

Don't go by voltage, as that changes over time. Look to see what the ECU sees....use the OBD2 scanner...

 

So unfortunately I have not found the cause of my no start issue as of yet. I did hook it up to a code reader after my original post and found no codes being thrown but did get a solid rpm reading while cranking for whatever that is worth. Is there anything that I may have done during the starter replacement on accident that would cause a no start issue? I did actually install new plugs because the ones in it had spent a small amount of time somewhat submerged under water at the bottom of a bucket so I had high hopes they were fouled and that simple plug change would miraculously cause my problems to disappear about that unfortunately was not the case and the xj6 is still sadly stationary. I may have even got a quote on what I'd get to scrap the thing.. just don't tell it that. ($140 if you want to know) But I'm kinda kicking myself right now because I know there was more I had to share I just can't think of it at the moment but if you have any ideas let me know!
Thanks!

 

Are you saying the RPM needle moves at startup? Usually a show of about 200rpms while cranking is supposed to indicate a good crank position sensor. I do believe there was a report of at least one incident where they were seeing 200rpms, but on a lark, replaced the crank position sensor and resolved the issue. It's a $30 part (no need for OEM here) and 15 minutes. (seeing RPMs apparently is not 100% guaranteed to sniff out a bad sensor)

If you have not replaced this part yet, it would be worth your while. It is a common issue.

 

There was reports a few months back of bad manufacture CKPS's being the cheap ones

The single signal that comes out is used to do a couple things and may not be satisfactory fulfilling one of them . and still not giving a code to boot . The fuel pump enable aspect is one common thing appearing from reading others although they may see starter RPMS on the dash

I once fried a CKPS ( confirmed with simple resistance meter test ) from hooking the main battery up backwards and the other instance I blundered on battery it didn't fry CKPS