Starting Problem

[DavidEm]

I wonder if anyone can help me with a relatively minor, but slightly concerning, issue with my 2001 308 XJR.

I have owned the car since October 2013 and it has always started pretty much on the turn of key, hot or cold. However recently, it has been reluctant to start and turns over for a good 2 to 3 seconds before firing up, with no warning lights. Once started she runs like a dream and performs as you would expect a good XJR to do. Run her around to get warmed up completely, turn off the ignition and on again, results in the almost instantaneous start as before the ‘fault’ appeared. But leave the car for about half an hour, i.e. still warm, and the 2-3 second turning over before starting comes back again. Odd or what?

So I trooped off to my local independent specialist - Keith of many many years experience with Jags - plugged in the diagnostic kit. Which found no faults whatsoever. A bit of head scratching ensued after which Keith suggested the spark plugs were replaced as they sometimes 'get tired', even though the car has covered just 55k from new.

Spark plugs replaced. Made no difference.

I have subsequently changed the battery. No difference, apart from turning over faster. I have also changed the batteries in the key fobs just in case it was a weird problem with the immobiliser or something like that. Made no difference.

Has anyone experienced this before? Any ideas what might be causing it, or suggestions of what I or Keith should try next?

Your help is very much appreciated.

[J44EAG]

Try changing the cylinder head temperature sensor. I`ve had a couple of issues in the past with V8 Jags in this respect. The sensors can get sluggish and throw strange readings at the ECU. They don`t last for ever. I`ve had two give up at around 80k miles. Use only a genuine replacement. Screw out the old unit, savage the seal washer whilst placing a finger over the hole. Insert the new part and then just burp out any air in the system.

Also remove the MAF sensor mounted on the tube exiting the air filter box. Two Torx self tappers are the usual fixing. Use spray carb or switch cleaner to clean the hot wire and glas bulb to sqeeky clean condition. Dirt can accumulate on the wire and bulb on the downstream side of those parts. Don`t touch with a screw driver or other hard tool. You may need to use a soft paint brush and the above cleaner to dislodge any muck.

Try that and see how you get on.

Mike K

[DavidEm]

Thanks Mike, I'll certainly give that a go. Although would a faulty cylinder head temperature sensor throw up a fault code? I have also had it suggested that it could be the fuel pressure regulator, but I would have thought this would affect the normal running quite markedly.

[J44EAG]

When my two CHT sensors gave up, no codes where itemised. Changing the sensors does help cold starting. If the sensor is a little duff, it can tell the ECU that the engine is hot when in fact the engine may be stone cold.

Try the replacement before going further. Regulator issues are rare and unlikely. CHT sensor sluggishness is a know issue when it comes to poor starting.

Mike

[DavidEm]

You're a star Mike. I'll keep you posted.

[DavidEm]

Mike, would that also be known as a coolant temperature sensor?

[J44EAG]

Yes. That`s the unit. M

[DavidEm]

OK, I have just changed the Coolant Temperature Sensor, but has made no difference unfortunately.

[Brakebuster]

part load breather pipe split ?

that gives trouble like this

BB

[DavidEm]

Thanks BB, I'll check it.

[ptjs1]

Jagslag,

My reading of your problem seems to indicate that the only thing that is different between an easy start and a difficult start is how long the engine has been idle. If you said the problem was only with hot starts, I'd be tempted to suggest that it could be fuel vapourisation, but as you imply that it happens first start in the morning also, I'd discount that. I wonder if it could be fuel pressure leaking back from the fuel rail once the car has been idle for a while. One way to check that might be to get your local indie to check the fuel pressure at the rail after it's been idle for 30 mins.

You could also try turning on the ignition, letting the pump run, turning off the ignition, repeating twice and then see if the engine catches quickly. It's not a definitive test or guaranteed to work but if it does it's almost definitely a fuel pressure drop. I'm guessing that there's some sort of pressure return valve in the fuel system that enables fuel to be returned back to the tank and it could be this which is failing.

Good luck

Paul

[DavidEm]

BELATED UPDATE: Shortly after reporting the problem on here the car wouldn't start at all. Would crank for England but not fire. No pressure at fuel rail... dud primary pump me thinks. Had both fuel pumps changed by my local Indy expert and hey presto! Problem sorted. Many thanks for all your help and suggestions.