Ive been trouble shooting some low voltage related starting issues on my 2009 FL2 manual rhd GS (Not stop start model).

Ive sorted most now by cleaning earths and installing a new Varta F21 battery and Starter motor earth lead as belts and braces.
I was wondering what the momentary expected voltage drop is (Im seeing briefly 8.9-9.3v lowest on my waveform monitor despite the new earth strap) when starting.

I was also observing some clutch pedal related voltage drop (Looks like alternator excitation voltage cut)
When looking at the wavefrom on my voltage monitor it seems to cut out the 14.3v alternator charge every time the clutch is depressed and released, -it drops by about 1v to 13.3v, returning back to charging after the end of the clutch pedal cycling.

I am sure this is intentional (is it linked to starting logic where it needs depressed?), removing the alternator charging during clutch function but can find no decent explanation as to why. It does not seem linked to the cruise as depressing the brake pedal has no effect on the alternator charging.

It only seems to occur a low speeds and stationary , not at higher speeds.
I have added the photo showing starting voltage drop, and the second one shows the clutch pedal actuation and release.
Finally -does the glow plug "curly" dash Icon only come on when the temperature is low, or at every key engagement?

My 4 yr old battery begins with 12.5v and drops to 10.8v during starting and charges at 14.6v.
I dont have a clutch.

Regarding the glow plugs; IIRC the glow plugs come on at every startup as it helps with cleaner emissions at start up and immediately afterwards, even if the ambient temp is not cold. The glow warning light only illuminates when the glow plugs are specifically required to aid actual starting in cold conditions.

There is an explanation in the JLR manual, but Ive not read it for a while. Jules

As Jules said. If it is cold enough for the glow plugs to be needed as a starting aid rather than to improve combustion there will be a delay between pushing the start button and the engine turning over. Then you might see the glow plug warning light but in 12 years I only noticed it a few times.

Thanks for the responses.
I expect the initial starter motor current draw drops the battery voltage. My actual drop varies depending on if engine cold, warm, just been in a long run, but the range 8.9-10.4v seems normal.
It is momentary.

The glow plug logic ( being on at all start ups) , but the dash curly icon only when cold seems counter intuitive, unless the current sent to the glow plugs varies between the normal starts ( ie short current blast) and cold weather ( longer current blast).
I checked using search for glow plug info, and see some folk say they put their foot on the brake before pressing starting button. My car you have to put your foot on the clutch. I’m starting to think this is why pressing the clutch deactivates the alternator so that it does not interfere with the system voltage on start up.

I’m interested in the glow plugs as whilst summer now I did have issues last winter starting when -6degc and colder and never saw the curly glo plug light once.

Last edited by flyinghorse1 on 13th Sep 2023 8:45 am. Edited 1 time in total

Don't forget that the electronic units depend on separate signal earth connections that may be getting corroded as time goes by.

It may be these that stop the electronics working together properly during the start up phase, as the large currents flow around the chassis from the main battery the electric bonding becomes more important. FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
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Brake or clutch depends on automatic or manual gearbox. Don’t forget that starting a Freelander (or any modernish car) is like booting a computer. If you go straight for a start with your foot on the relative pedal you are starting things like the ABS pump and all the control modules at the same time as the starter is calling for power. If you turn the car On, by not pressing the relative pedal when you press the start button you allow the cars systems to turn on and be ready for when you put your foot on the pedal and press the start button. This would have also activated the glow plugs.

It's always prudent to allow the system to boot before allowing the start. Not doing so puts an enormous load on the battery, which can lead to data errors due to voltage drop.

The battery voltage should never drop below 9.5 Volts when cranking, as there needs to be a buffer before the low voltage (8.5V) CRASH status is set.

The alternator drop off is a strange one. Are you allowing the RPM to drop off when the clutch is depressed, or holding the RPMs and dipping the clutch? Hyundai Ioniq 5 Ultimate. The family car.
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A few notes on amps jump starting. https://www.freel2.com/forum/topic38359.html

Let's say for arguments sake 280 amps for a 4 cylinder 2.2L diesel engine with a 80AH battery. My guess even for a new battery (really not exactly large AH in the scheme of things, Freelander really should have 100AH battery) is a least a 2.5 voltage drop, my guesstimate (I should have measured voltage drop as I have many multimeters)

Not to forget when you press the key fob to unlock the car, the car will already fire up the glow plugs for non petrol engines. So by the time you open the door (for new Wifey or New car!), get in the car, put on the seatbelt/s, you are not really aware of the 4 x 15 amps being supplied to the glow plugs has been going on for some time... & all the other BS to fire up a Land Rover! (I can hear the background circus on the 2.0 litre petrol engine).

I have jump started myself from 4 x 26AH batteries (for fridge) twice, & that is with a well maintained & 4 year battery replacement (a basic rule of thumb is a starter battery loses 20% of its capacity each year)

The starter battery is taking a hammering in less than ideal weather, so you need options, if you are in the outback a 1000km from help... Handy in the city as well (to impress Wifey that you know what you are doing... even if it is a smoke screen!)

A 2.5 volt drop or there abouts I don't think would be an unreasonable run of the mill scheme of things. Procrastination, mankind's greatest labour saving device!

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Thanks , some good comments.
I can see why brake to start on auto makes sense. Mines manual.

Re the alternator charge dropping/ stopping during clutch depression and release at idle and low speed , there’s minimal variation in rpm( not noticeable on tachometer).
It feels deliberate ( ie by design) as the on /off action is very steady/ repeatable on the wave form image.

Regarding the battery voltage, you can see that anything other than a 12.3v-12.5v plus battery is needed before activating crash status given the starting voltage drop. I need to figure how to clear the crash status without going to dealer)

A lead acid battery is considered discharged if its resting voltage is below 12.6 Volts. My 18 month old battery Yuasa HSB110 holds 12.8 V when resting, and over 10.5V when cranking over.

I'll look into the alternator voltage drop off on mine.

Crash status needs to be cleared using suitable diagnostic equipment, like JLR SDD or GAP IID, but others may do it too. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.