Nissan Repair: Infiniti Q45: What is wrong with it?, 1991 infiniti q45, infiniti q45

Question
I own a 1991 Infiniti Q45. A re-manufactured ATK engine was put in it in 2000. Last year, during a winter storm, factory alarm system started going off on its on in the middle of the night. I went out and shut it off like four times. Next morning, the car would start, but the engine would not turn-over. Upto now, the engine starts, and after about 30 seconds, a thud sound emits from somewhere the ignition stops. The engine does not turn-over.
Three mechanics have given me different explanations. Two of them blames the timing belts. The other mechanics who actually look at the car, says the computer system is damaged beyond repair. All require substantial amount of money to fix.
Can you please, give me your expert opinion, before I choose to do anything at all.

Thank you.

Maurizio Ochen-Otto
317 797-4693  

Answer
Maurizio,

I would check to see if the engine will rotate with the starter.  If you have a fully charged battery and it will not turn over turn the engine over, by hand with a socket on the crank bolt and breaker bar.  If the engine is stuck you are looking at an engine replacement.  If the timing belt is broken or has slipped and the valves have hit the pistons that means that the engine is going to have to be taken apart.  If the engine does turn over freely then you have a computer problem and the ecm will need to be checked to see if it is killing the engine due to the alarm malfunction.  Email me back and let me know what you find.