Toyota Hiace supercustom PROBLEM

Hey guys,

My recently bought 1996 Hiace Supercustom Limited 4wd 3.0 1kzte with just over 100.000 km has some problems. When i bought it it has been sitting in someones yard for 1-2 years. I changed the timing belt waterpump and did the oil change by a mechanic. The car still had problems starting and also has a rough idle and then stalls. Since ther was 1-2 year old diesel in the tank which i bought and drove it with i thought it had just a bad fuel filter. I switched the fuel filter but the idle problem and stalling is still there. There is also a bit of white smoke at the beginning and sometimes a slight rhythmic knocking noise in the engine which comes and goes. Stays for maby 5 seconds and then goes and then comes back at times. I also have a glowplug light at the dash which dometimes stays on the whole time even when driving and sometimes it doesent even show at all. Also since i have the limited i have a digital gauge cluster and the fuel gauge is sometimes showing full and then sometimes showing like 70% full. Maby some electrical problem because of the long sitting? What is it? Bad glowplugs?? Mechanic said th are fine but idk i dont really trust this mechanic anyw V I dont know what to do anymore i need some help here.