Please can anyone help. My friends XK8 is a non starter. He said it did start then stop and it wont go since. It cranks over at the right speed. He said he checked the fuses and a 10 amp had blown in the fuse box on the left in front of ECU compartment on the left side of the car. Looking at the engine from the left he seems to remember it being on the right side of the row towards the bottom. Anyway I have checked all the fuses and relays and all are good. Fuel is fine and the right pressure. Pulled of the vacuum pipe from the regulator and no fuel is present in the vacuum. I tried park and neutral just in case it was the auto inhibitor switch. Had the plugs out and cleaned all them with a blow torch and no wire brushing. Had a spark on the plugs and a new plug I just stuck in the lead to check that, same. I don’t know if the spark is good under compression or at the right time. Injectors are getting a single to fire. Tried easy start down the intake pipe but it does not even try to fire.

So I started testing coils. All coils are getting there 12 volt feed. All grounds are working. Gearbox ground looks Ok. All wires from coils to ECU have been tested and all good. Workshop manual states though that all the eight wires from the coils which are yellow with a green band (tracer) should not have more than 1 volt on them. I have 4.5 volts. Connector EM 83 pins 10 and 11. Swapped around relays with others of the same amperage. Took the engine ECU apart and studied the board as I have been told the capacitors could be blown. Cannot see any damage on the board and visually cannot see any swelled or leaking capacitors. Looked at temperature sender but I have not yet looked at resistance to temperature as the weather is awful and the car is outside with no cover. But I will be doing that next. I have not carried out any load test yet only with a multimeter.

Tried three code readers and no engine DTC’s. Engine cams are turning so I don’t think its mechanical. Prior to this the car was running lovely. I am not a professional just a hobbyist and just look after my own cars. I am not sure where to go next to try and help him. If anyone can help us, we would be most grateful.

 

Could be borewash. Are the plugs wet?

 

Hi.
Thanks for the reply.
I run it without the plugs and burnt all the crud off the plugs. It appatrentley started then just cut out, since then no start.
Regards

 

Two questions:
You say that the manual wants less than 1 volt on your coil wires, but you have 4.5V. DO you know what that means?
Have you considered that you might have a bad crank or cam sensor?

 

Thanks for the reply.
I will have a look at them but possibly naively I thought the scanner would have picked this up. I also thought the rev counter wouldnt work when cranking or that I would not get a spark.
Tommorrow going to unplug all the coils and see if the 4.5 volts drops off. I wondered if a coil has gone rouge.

Regards

 

I was wondering where the OP got that figure from. To the OP, can you share the source of that (ideally a screenshot of the page in the manual)?

 

I have no idea how to add a screenshot. Never added pictures only text.

 

Google how to take a screenshot on your device, then click on the image button to attach it.

 

Thanks for the help.
Update I removed all coil wiring plugs and checked the yellw green tracer wires. I actually have nearly 5 volts with all coils disconnected.
Checked crankshaft sensor at the ECU Plug EM83 pin 08 yellow and pin 07 purple. Briefly had 4.000 ohms then went of the screen. Checked Cam sensors ECU plug EM83 pin 19 green and pin 09 brown and cam at ECU EM83 pin 18 brown and pin 17 orange both gave a reading of around 1.900.
Regards

 

Th G/Y wires to the coils are monitors for the ECU to determine their health and should not have any significant voltage on them. have you checked the voltage at the other connectors going back to the ECU? Checking the wiring for shorts to anything and also checking the voltage from the ECU. (which should be logic LO, or less than 1V)

 

Assuming that doc you posted is for your model year car (is it?) then you do seem to have identified a problem. I would focus on that before doing anything else. Follow Twinsemi's advice above. You need to try and determine where this short is, or if it really exists, or if it is problem in the ECM itself.

I would also check that 5v with a test bulb, rather than just a multimeter to make sure it's real.

 

It does seem an odd one, and you have already done a lot of the checks

I find it odd that the motor doesn't even 'kick' a little in response to the engine start spray - when you have spark and the injectors are effectively bypassed?

A problem with either of the ignition monitor loops for the cylinder groups won't, of itself, prevent the engine from starting. The EG shows to expect a ~23Hz (at idle) 5V p-p waveform fed back to the ECM connector pins 10 & 11.

The ECM controls power to certain sections of itself:- it's worth checking F10 (5A) and the associated EMS control relay - both in the Engine Management fusebox.

There are 4 separate feeds to the ECM:



59E & 60E - F10 (5A) Engine management fusebox
56II F5 (10A) Engine compartmentfusebox

You should see B+ on the injectors Black/Red feeds with ignition on (ii)

 

Sorry to everyone for the delay in answering. I have only been able to get back to the car this week.
I went back to basics. Air in, spark, fuel and air out. All that checked out. As it would not run even with easy start I thought I would check compression as I was running out of checks to do. I stupidly ruled out compression as prior to this problem the car started first time everytime and no prior symptoms like rough running, smoke etc. The compressions were terrible down to 55, 65, 60,100, 100, 100, 70 and 120 psi. poured some oil down the bores and compressions raised for example the 55 psi cylinder raised to 80psi. I tried to start the car and it almost ran, coughed for a few moments then went back to no even trying to fire.
Question is the engine finished as in worn bores and rings. Is this Previously helpers in the forum have mentioned bore wash. The plugs have been out for over a week and everytime I have tried to crank it over for testing I have had the fuel pump relay out, or in the case of compression testing throttle wide open. The jag has done 160,000 miles and the engine number is 121951 (if that is the original engine) so if I am correct that this is post Nikasil. I am not sure where to go or what to say to him. Is it just a one off where he kept trying to start it and borewashed it. I have no experience of this issue and would hate for it to happen again especially if were out somewhere. Luckily it stopped working at his home.
Any advice would be much appreciated.
Many thanks to you all.

 

If the rings were worn/broken it would have been smoking badly previous to the no start issue. Adding oil to the cylinders should have cured bore wash, so I'm wondering if the low compression is due to bent valves resulting from chain tensioner failure.
I would remove the cam covers and rotate the engine by the crankshaft bolt to see if the flats on the camshafts line up.

 

An early MY2001 could still have nikasil bores. The engine changeover # is 0008181043 (Aug 18, 2000) and can be found here:



If a factory reman motor has been fitted, there should be a plate on the RHS of the block near the bellhousing:

 

Yeah, the engine number doesn't make sense. (probably could see all of it) I use a cell phone camera and bring it up next to the LH side of the block on my 2002. A flashlight (torch for all you Brits) is helpful to get light in there. Should be the same for an original 2001.

But that's not why you came here, is it!

I keep thinking spark is the issue. Have you tried reloading the distributor to make sure that you're not 180 degrees off on the camshaft? LOL
The point is, how sure are you that the #1 cylinder is getting its spark near TDC on the compression stroke? Any way of putting a timing light on it to see?

 

Well it runs now. I put oil down all the cylinders and cranked it over while feathering the throttle. Obviously a lot of smoke from the exhaust. I think because he doesn’t use the car much the battery went dead. The charger was next to the battery and testing the battery only shows 50% of health. Now I have found out the he thought the starter had failed as it was turning over slowly. He kept trying to start the car and I think this created the condition for bore wash. Bought a 100amp Yuasa battery and some new spark plugs to fit and hopefully this was just a one off problem. I will check the engine number as suggested. If it runs ok then I wont check the cam timing but thanks for the suggestion.

Thank you to everyone who sent information and tried to help. Indeed it was the help that made me look at the problem of low compression and bore wash. Having never experienced this before and the fact that he said it was running then just stopped sent me down the wrong path to diagnos the problem.

Thank you all again

 

Well done for persevering and solving the problem and thank you for coming back and updating the thread. It will no doubt help someone in the future with the same issue.