Exploring a problem with my 09 Freelander 2 and it's injector(s). Suspecting a faulty earth based on some previous feedback. Can someone tell me how they are earthed. Where are they earthed to?

Many thanks.

They are switch by the ECU to earth

To check the injectors use an ohm meter and check the impedance, then probe each terminal and the body of the injector to make sure an injector hasn't gone to ground, but with Piezo injectors the only way to test them for sure is with an AVO meter than can produce a 500v discharge test.
Injectors are the heart and soul of the engine, very few can test them, very few understand actually how they work and even less know how to diagnose them, worse still very few know how to fit them correctly.
The tightening torque is critical as "outside" the parameters changes the shape of the body !!! which in turn changes the amount of fuel injected and can cause misfire, knock or smoke.

Secondhand injectors in my opinion are a waste of time, find a diesel specialist with a reputation for repairing or supplying them and take their advice and pay for the testing. it could be £120 just to get them tested, but its cheaper than throwing bits at it and guessing.
Unfortunately almost 99% of the faults I see in diesels are as a result of inferior parts, lack of maintenance and miss-diagnosis.
I don't supply injectors at all under any circumstances and will only supply and fit on a job diagnosed by myself
Once its confirmed injectors are faulty ( if they are ) then the cause needs to be found as well.
Many times I have had to remove a fuel tank and thoroughly clean, clean every pipe and filter housing.
Has it got a cheap diesel filter ? did it just come apart inside and the debris seize the injectors.
I did mention in your previous post debris as small as 2 micron will seize them up or may be diagnosed as blocked.
Many questions to be asked and checked so it doesn't repeat. Jaguar x-type sport gone
Jaguar x-type 2.2d sport one of my best cars ever sadly gone
Freelander 2 GS auto 2008 most unreliable ever ! gladly gone
Freelander 2 GS manual 2013 only time will tell !

Surely the fact they are bolted to the engine means that they will be earthed like everything else? Past: FL2 TD4 HSE Auto
Evoque SD4 Dynamic Lux Auto
Present: Audi A3 S Line.

no they don't earth to the engine, they are earthed by the ecu. IF they leak an electrical current then they fail, can often fail in pairs when that happens. Jaguar x-type sport gone
Jaguar x-type 2.2d sport one of my best cars ever sadly gone
Freelander 2 GS auto 2008 most unreliable ever ! gladly gone
Freelander 2 GS manual 2013 only time will tell !

just a thought,
i would be using a scope to check all 4 injector signals and current load.
has the supply voltage to the ECU been checked at cranking, if 2 injectors are unplugged and it fires I would as one of my tests check the supply voltage at the ECU and the earth for zero voltage at ECU earth pins.
Technically it should flag a low voltage fault if it were caused by a voltage drop, but part of proper diagnostics is eliminating any other possibilities before chucking parts in.
Had the same issue on a Sprinter once where the supply voltage dropped to less than 9 volts under load for the ABS module and it was a high resistance in a wiring loom. Often I find these using a thermal image camera. all it needed was a modified supply loom and it cost about £90.00 to fix. A previous garage had fitted over 2800 quids worth of parts ! Jaguar x-type sport gone
Jaguar x-type 2.2d sport one of my best cars ever sadly gone
Freelander 2 GS auto 2008 most unreliable ever ! gladly gone
Freelander 2 GS manual 2013 only time will tell !

Thanks oldgeezer - Nothing but silence coming from my indie specialist at the moment since they told me they were going to mix n match my old and new set of injectors. My next step will be to get all the injectors tested at TT Automotive, who are my local diesel specialist. I will also pass on your comments/suggestions in an email.
A month off the road now. I will probably cut my losses with it after this experience.

hope you manage to get a resolve, and all this assuming its injectors. I hope someone did investigate rail pressure at cranking and holding pressure, if they are not within threshold that two will shut the injectors down, so many scenarios.
Now days its cheaper to go to a specialist first.You pay more but usually a first time fix.
I think your bad experience is more down to people looking at it not having the in depth knowledge or understanding of the system. Jaguar x-type sport gone
Jaguar x-type 2.2d sport one of my best cars ever sadly gone
Freelander 2 GS auto 2008 most unreliable ever ! gladly gone
Freelander 2 GS manual 2013 only time will tell !

I think you are spot on. The first old boy I spoke to on the phone suggested a diesel injector specialist straight away. Kidded myself/ lead to believe that the garages would sort it.
Will keep you posted on the outcome

is it finally sorted and running now ? Jaguar x-type sport gone
Jaguar x-type 2.2d sport one of my best cars ever sadly gone
Freelander 2 GS auto 2008 most unreliable ever ! gladly gone
Freelander 2 GS manual 2013 only time will tell !