I have a caterpillar d6n serial number cck00666 it's very hard to start even when it's warm I change both fuel filters when you crank it there's a lot of white smoke coming out of the exhaust once it gets started it seems to run fine couple days ago it bogged down for a minute or two we assumed it was a bad fuel filter hasn't done it since after I changed the fuel filters I let it idle for about 15 minutes shut it off went to start at about an hour later won't start again you have to crank it for over a minute to get it to start