need some help for my father inlaw.
X300 4.0
This is his description by the way
He was driving a few days ago and said it was 'playing up' cut out and running rough.
Limped it home , went back out next day to see if it was playing game or playing up . now wont start or turn over
Garage have checked all sorts but diagnostics say immobiliser codes don't match

Any ideas guys before it goes to the jag specialist and he has a big bill looming

 

Hi maccavvy,

It seems unlikely that the security system would have caused rough running, though it could have something to do with the car not turning over now. My first suspect for a security system issue or no crank would be low battery voltage. Did the garage load-test the battery or note a problem with the charging system?

If the engine will rotate but not start, watch the tachometer while cranking to see if it reads about 200 rpm. If it reads 0 rpm, suspect the crankshaft position sensor (CKPS).

A primary suspect for sudden rough running would be petrol contaminated with water. Had he refueled recently?

Another suspect is a failing fuel pump. Did the garage test for fuel pressure at the fuel rail?

Did the garage scan for diagnostic trouble codes (DTCs), and if so, can you please post them all here exactly as they appear, including the letter P and four numerals?

Also, please tell us the model year because there are some differences between early and late X300s.

Cheers,

Don

 

Something you can do in the driveway is to swap the fuel pump relay as it may have gone bad . Feel for the relay to click on for 4 seconds then click off as you rotate the key to on position before start position . Because it clicks doesn't mean the relay doesn't have bad power contacts inside .

The ECU will not start the car below someone said 11.5 volts .

Don B has good recommendations but these you can do yourself in the driveway .

By not turning over do you mean no rotation with the starter or no light off with rotation ?

 

i dont know the codes yet. garage has a snap on solus and just said immobiliser codes don't match ill find more info

it does nothing on the key .. no click turn over or anything

it had a new battery 2 months ago. and they've had it on charge at the garage

 

I suspect the code they found will be P1621. This is very likely a ghost code and is present in many cars all the time with no issues.

 

By not click , no turn over ( rotation only at his point ) put your finger on the starter relay and feel for that specific one to click . This will verify you have the commanded ground provided through pin 1 on the ignition switch . With the Key in the on position before the start position you can remove and reinstall the king relay's in the corners of each fuse box . Feel for them to click as they get their commanded ground through a different contact through pin 2 on the ignition switch . 5 fuse boxes with the exception of the LH engine fuse box which is the horn relay . They all get their ground path on pin 5 to the car frame . You can remove the lower steering column cover and get to the switch connector , my pin 5 was corroded .

By the relays clicking doesn't mean the relay is good as the power contacts inside can be bad so the relay can be swapped out .

New batteries being junk these days I would start with a battery check for a open cell and you may have to warm the battery up as it is charging and tap on it with a 2 x 4 to watch it open .

All the fancy smancy tools won't find the basic needs of simple wiring integrity .

 

Hes decided to send it to a jag specialist as hes getting nowhere with the locl garage .

I think simple things are out of their depth . ill update once its fixed