Hard starting backhoe

just rebuilt the motor on my 310 john deere backhoe back in the summer, also had injector pump and injectors done as well, plus rebuild on start as well, ran great very smooth lots of power started great, till the temps out side have started to drop will start great till temps reach about 50 degrees anything lower then that it will just puff a little smoke not try and start at all unless block heater is plugged in, before rebuild would start even when temps would 0 with no heat, engine seems to be turning over fast enough, what am i missing

Were the original valves and seats ground and re-used, or parts replaced as needed to keep the valves face close to new spec? When diesel heads have the valves too much below spec that will KILL compression cranking heat needed for cold starting, although engine may run fine after starting. My White forklift had the same trouble when I brought it home, did a compression check, all had 300 PSI, ran OK but started hard cold. Pulled the head and found all twelve valves below flush and should be ABOVE .040 inch on that engine. Had the head repaired with all new seats, now the compression is 350 and starts as it should cold.

All new parts in the head, day even switched out injector pump from another engine with hopes it was a bad rebuild on injector pump. Have checked compression it is 325, book on it calls for 300 psi. I am hoping few more hours of run time will help. Thanks for information.

Do you have a history with this machine? Plainer put, did it ever start well in the cold? Many Dubuque Deere engines started poorly as you describe since they were brand new. Problem got real bad in the 80s. One time we had two brand new 350Cs.D Note -brand new. One would start at 30 degrees with no ether and very little smoke and skipping. The other one would just barely start at 50 degrees F and when it did- it skipped, sputtered, smoked, etc. Once warmed up - it was fine. Deere sent an engineer over to us from Syracuse. We worked together,checking over and tearing apart both machines. We started taking parts off of the bad starting machine and putting them on the good starting machine. When done - the good starting one had the pistons, head, camshaft, starter motor and injection pump from the one that started bad. Guess what? It still started great.

Deere later came to the conclusion that piston-standout was the main issue. No way to correct it on a bad-starting engine without special made pistons.

This is why I asked about your history. If you had a machine that was already border-line and you then ground the valves too deep -it will make it worse. That said - I have pulled the heads on good starting engines - sank the valves way deeper then they ought to be - and when done - they still started great in the cold.

Regardless- valve-heads should be kept at .030" and.050" recess if possible. Engine cranking speed and fuel delivery at that cranking speed also must be right.

So what would have happened if you just ground the surface of the head to put the valves back down to flush. Were they so deep in you could not bring them back flush?

That would not work on the White/Waukesha head. Mine was really bad, all valves .040-.050 below and spec calls for .040 ABOVE. Reason they need to be above is the pistons have a DEEP .140 inch valve relief cut, so the valves need to be above to raise the compression. If the pistons would not have the deep valve cuts valves would work fine flush.