Hello all,
My 1998 XJ8L will turn over but not start. It doesn't even try to fire, acting as if it had absolutely no gas in it (and I did add a gallon of gas, thinking it might've been out). The only anomaly is the car was sitting for 24 hours (a rarity since it's my daily driver), but prior to parking it the car was ran on the highway for 30 minutes. I don't think it could be cylinder wash since it wasn't started while cold and then turned off a short time later.
I've never had a non-start issue with this car, and I can't think of any prior issues that may contribute to this problem. I did replace the timing chain and tensioners a little over a year ago and it's been running great since then.
I didn't get a chance to do any kind of troubleshooting (this happened at 3 AM last night), but I'll be heading out to look at it after work today. I didn't smell any fuel at all from the tail pipe after cranking it, which would tell me I'm not flooding it. I'll try pressing the pressure relief valve on the fuel rail to see if any fuel shoots out, that should me if the fuel rail is at least getting pressurized.
Any ideas to take with me to help diagnose this problem would be greatly appreciated.

 

If you have fuel pressure, you could be dealing with two problems: Whatever kept it from starting and cylinder wash on top of that. Here is a link to Gus's no start assist:

JagRepair.com - Jaguar Repair Information Resource

 

Is the jags dash lights come on? Are the operating normally? Try touching the negative to positive on your battery and then try starting it

 

Princemarko - all of the dash lights come on, and everything appears to be functional just as it would be right before starting the car normally. The doors lock and lock fine, which would lead me to believe the inertia switch hasn't been tripped. I did disconnect the battery, but only for about 30 seconds, and I didn't touch the two battery leads together after disconnecting it. That will be the first thing I try this evening.

RJ237 - I wouldn't suspect cylinder wash would be the main culprit, since it was up to temperature right before being shut off. A few time I've left the car sitting for a few days and it started right up. Nonetheless if it seems to be getting fuel pressure then I'll try putting a little bit of oil in the cylinders.

Thank you for your replies, I'll be headed out to work on it in about two hours, hopefully I'll make some headway.

 

Update - I tried resetting the computer, to no avail. I can't hear the fuel pump running when I turn the key on, and I tried swapping the fuel pump relay which didn't help. I'm going to double-check my diagnostic steps, but it looks like a faulty fuel pump.

 

The wash doesn't happen after 30min of highway driving. No way. I think this can be eliminated.

My guess,.....no fuel delivery. Fuel pump circuit blown, or pump itself died a sudden death. Do you hear the pump whine when you turn on the key? I bet not. Have someone turn the key, while you stick your head in the trunk. You should be hearing the click from the relay, and the pump whinning.

If you have fuel pressure at the rail, then you don't have a spark (easily checked). The only other component of the start is air. But none of these systems have a tendency to suddenly quit working, except the fuel pump.

Oh well,....I was typing while you were diagnosing, and posting. You are on the right path.

 

danielsand, my point was that if he had fuel pressure and was cranking without starting he was introducing fuel to the cylinders. This had nothing to do with running for 30 min. the prior day.

 

Gotcha.

Looks like he figured it out anyway. Pump is bad.
You are absolutely right. Cranking without the spark (with plenty of fuel!), WILL wash the bore. I think he never had any fuel to the injectors. I've seen the pumps working one day, and the next day, they are DEAD, out of the blue.

 

I could not hear any fuel pump noise at all, and I was checking with my head right in the trunk, with my ear pressed against the open filler hole and under the car. I didn't hear the fuel pump relay clicking, but I wasn't listening for it. She's getting towed home today so I'll double-check the relay before starting on dropping the tank to get the pump out.

 

Just a quick update - it was the fuel pump. I was completely unable to undo the fuel lines underneath the fuel tank, but I was able to slide the tank out enough to get the sending unit out (I was being very careful to make sure I didn't break the fuel lines underneath). Big thanks to everyone here who helped me come to my diagnosis, as well as those who posted the detailed fuel pump replacement posts