Hi, I have an X300 3.2 1996. It has an intermittent no crank issue.

Problem: when the voltage is not high it will not crank, and the “check engine” light goes out on switching on the ignition.

Only if I can get the voltage high enough (around 13.5 volts usually with a fully charged jump pack) then the check engine stays on and it will start. Once it’s running the battery charges up enough to allow to start. I have tried charging the battery with a charger and can’t get it to the magical 13.5v.

I have changed the battery twice, and even switched with a known good battery from another car. Still will not start.

I have changed the immobiliser unit in the boot, and matched it with a chipped key, I can get it to start with that but it still has the voltage problem.

also - don’t know if this is related - but the battery goes flat after a few days.

could someone tell me how the ecu works out the voltage is high enough to start- and what is the voltage that this should be? As 12 or even 13v is not enough for my jag ecu to start.

Silly question but does it measure it via the clocks?

any help or suggestions would be great. Thanks

 

A fully charged battery is 12.75 and is charged from the alternator between 13.5 and 14.5 only after engine running

Somewhere along the line I picked up on 11.4 needed for start carry on forward beyond just starter rotation as the ECU drops out the fuel injectors , the starter will still rotate strongly below 11.4

Going flat after a couple of days can be the battery in this heat or a common parasitic drain that a quick switch trick to overcome and get back to later

Rotate the small rotary knob on the cars left on the steering collum from auto to off , seat and steering movement negated on removing the key

Do not install the battery in backwards , positive post fwd , ask me how I know ....................twice , you can mark with arrow on white tape

Do not overtighten the battery positive post bolt , breaks saddle curved nut underneath , ask me how I know ............................once

Keep asking questions and your 3.2 starter circuit is a tiny bit different then the more common 4.0

Getting a lot of rain in England and fuel fill cap well draining water ? This affects the electrical connectors ( starter rotation enable from the SLCM ) under inside the upper area of the trunk and not so much the fuel in tank quality

The gauge is very accurate minus heavy battery cable nuts loose and current draw on things like starter , cabin fans ( current / voltage trade off in restrictions in connections or item current draw )

There is a nut ( s ) check



This is a pic of the 4.0 system

 

You will never get 13v volts from a 12v battery. As @Parker 7 said, 12.6/12.7 is very good, and 12.0v is should be perfectly adequate to start an X300.

You may have a high resistance connection somewhere between the battery and the fuseboxes that power everything. So, even if you have 12.6 at the battery, the resistance could drop that down to 10 or 11 v at the point of use. Check the battery voltage at the fuseboxes in the engine bay and at the rear seats.

Common failure point is the connectors through the bulkhead that corrode and cause voltage drop. Follow the thick black cable from each engine bay fusebox back to the bulkhead to find the connection point.

 

Someone had excellent pics of the 1st battery cable terminal connection as you look down through the intake pipes , it comes loose but this is another pic

13 mm socket on a 3 inch extension






The 2nd connection is the terminal post inside the engine compartment on the right wheel well , you need to remove the battery cable and wiggle the bare terminal post

The 3rd is under the rear seat pan as you remove the seat pan so this is your last check




The 4th is right after the positive battery post as it turns down and comes fwd

This is a pic of the V - 12 engine / transmission starter circuit which is close to your 3.2 setup

 

Brendan brought this up last week on another car as an important point :

All this power " going to " the starter depends on the starter mount bolt / engine block ground strap to car frame

Best got at from the bottom , 13 mm on the starter mount bolt and either 8 or 10 mm socket on car frame bolt / clean with wire brush on car frame and strap end , preserve with light bulb grease as those small packets at the auto parts store cash register

This ground strap stud on the chassis can degrade , you will see good voltage on cranking as the restriction is after the starter

 

If the battery is known to be good and goes flat after a few days there must be a parasitic drain that is running it down. A good fully charged battery should not run down so quickly.

 

thanks for all the replies.

yesterday my jump pack was at 3 lights (high charge) which usually starts everything. I got the multimeter out and it read 12.42 volts. I tried this on the X300 and “check engine” still went out and no crank.

last night I put the pack on charge, and this morning it read 14.4v, and the fully charged light was on. I fully charged the x300 battery at the same time. It read 12.7v. Refitted the battery, no crank and check light out.
connected the jump pack, and tried again, check engine stayed on and it cranked and started. Watched the car gauge go up to 14v, took about 10 seconds. I turned off, restarted a couple of times and switched straight off. No issues. I removed the jump pack and now it restarts without it.

I then just had ignition on, not cranked up, turned on full lights and waited for a few minutes. The voltage on the meter eventually went down to around 12.4v (less than what it had earlier with the no crank situation). I turned off, turned the key and it cranked.

so how is it that it cranks now on 12.4v without a problem, but didn’t crank on 12.7 volts earlier?

I know I have a current drain, I’m working on that issue next, but trying to work out this intermittent no start issue.

 

The starting with the charger and not without points to the battery

Even though you see good voltage the current is lacking

12.0 volts is about 80 %

After the engine is warmed you have less starter demand / load so more successful chance of starting

After battery is warmed in a start / recharge cycle it has better chance of providing needed current to start again

To add another layer of consideration by having 2 power sources you are overcompensating an issue like current limiting heavy battery cable connections

 

Gone are the days of Jaguar batteries mounted on the bulkhead, easy to access and remove, with cable connections that didn’t break and under three feet from the engine and starter motor, minimising voltage drop.

 

The voltage issue on the X300 is normally associated with a crank no start problem. Everything to do with the starter is relatively voltage insensitive, and she will crank well down into the single digits voltage. What has been established though is that the ECU and other modules don’t like anything below 11.something volts, hence the crank no start. If you aren’t cranking, I doubt that voltage is your problem (apart from total absence of)