I agree with Haydn, glow plugs are 90% the cause. I am also replacing mine in about 2 weeks. Come winter time they show their true working condition.
Just be ready for the big shocker, I bought mine last month from Midas and they cost R449 EACH, almost R2000 for the four glow plugs.
What I usualy do when my glow plugs is shot and just before I change them is to add some Spanjaart Injector Cleaner to a full tank and only when tank is driven completely empty I change the glow plugs. Reason being that I have found that Injector Cleaner is not good for glow plugs.
Some members have different views on additives, but this works for me and it helps to improve fuel consumption.
BTW, the glow plugs you want to get are NGK CY-55, ceramic coated tip. They will last you a very long time. Don't go cheap, not worth it.
2003 Colt 2.8tdi DC 4x4
Camil Suspension, Core Off-road Ball Joint Spacers, Mikem Extended Greasable Shackles, Load Hog Helper Springs, Turbologix Digital EGT, Aluminium Canopy, 63mm Down Pipe and Flexi + 58mm Free Flow, Snyman 4x4 Bullbar, 31" BFG KM2, NL Dual Battery System, 1000W Samlex Inverter/Charger, Petoors Snorkel, Rear View Camera, Rear Spotlights
Everything Works Better When It Is Properly Lubricated!