I have a bobcat t550 that isn't starting... we changed the injectors, fuel filter, & put a brand new 1000cca battery in it but no luck.. it starts and runs fine with a small spray of starting fluid, but after I shut it off and try again it won't start. I get a m2303 code (starter relay) but I'm almost certain that its because of the long crank. the injectors tested just fine. No leakage and no starvation. the PSIs in the pump are also good, so its not the pump. the only thing I'm getting is low RPMs @ 320 when I should be running at 500 to start, but with the new battery it should've fixed that problem..
Is it possible that the starting fluid is raising the rpm’s enough for it to start.. Do u have a common rail inj pump or the small PFR inj pump?? Commonly referred to as a cassette pump.
A sticky Bobtach valve can do this, the Doosans are very picky on crank Rpm. Does it seem to start in strong then slow down as if loading a bit? Remove the drive belt and try to start it that way. it will code and shut down on charge pressure but helps narrow it down. If still slow try a new starter. 9 times out of 10 a crank no start on the Doosan is injectors, but sounds like you have that checked out. What is your rail pressure while cranking? Is it at or above desired rail pressure?