checked my Nitro this morning and yes the relay is located on the top of the PCM, inside edge of Left Front Wing.

 

No i'm not 100% sure, i'm just going by a variaty of manuals, but info on the 2.8 CRD engine is very limited, i did read it could also be next to the PCM, rear left of engine compartment maybe on the left inner wing.

i did find a couple of pics for the relay, some looked like the size of the one in your pic, but also found some that looked like the size of the one i showed.

however finding it should be easy, just follow the wire from the Glow Plugs it will go direct to the Module ( relay ).

take note: the jeep liberty 2.8 CRD engine which is what comes up when you search 2.8 CRD is different in lots of ways, the whole glow plug system is different, wiring, voltage, glow plugs and relay.

 

Are you 100% sure that's the module as the modules I've seen online don't look anything like that

 

here is a pic, lift the cover, the Glow Plug Module location should be on the underside of the cover, or this complete unit is the Module.

 

here is a pic, lift the cover, the Glow Plug Module location should be on the underside of the cover, or this complete unit is the Module.
View attachment 22736

I've searched this and the part you have pictured is something to do with the aircon/ climate the part I've ordered looks nothing like this

 

I don't suppose you have a diagram of module location?

 

It's not a fuel issue as far as I'm aware when it actually starts there no smoke at all. It only struggles in cold temps . I removed the electrical plug off one of the glow plugs and plugged an old glow plug i removed which works after testing and earthed it off the neg battery terminal , turned ignition on and no glow at all , not even getting warm. So defo an issue with the power -glow plugs , next step in my mind is the module that turns the glow plugs on/off, checked fuses and the module fuse still intact .

 

firstly the glow plugs i believe there called fast plugs, and they are very quick at getting hot, so the fact that the light goes off very quick is normal (my Nitro does the same ).
i have looked at the wiring diagram and there is a fuel heater within the fuel filter, there is also a fuel temperature sensor (this may be faulty ? ), still looking at the wiring diagrams for what controls this

Glow Plug Module: the Glow Plug Relay is actualy the Module ( located on the Bonnet slam panel ).
the PCM ( ECU old school ) sends a signal to switch the glow plug module on and off.

did look online, someone had replaced the glow plugs and the glow plug module (relay) and made no difference. someone also suggested that it could be a leaking fuel injector ( could make sense if you are getting smoke when the engine does start ).

someone also said they where not getting the correct 4.4Vdc supply at the glow plugs,( yes thats correct the Glow Plugs are NOT 12Vdc so don't test them a 12Vdc supply ).
thats all i've got for now, will have a look at a few other things as soon as i have a spare 5 minutes.