[Little]

Did you try removing the cap? Before I got towed I'd keep pouring water in, even running a hose to the fill. Towing is an expensive crapshoot. I don't remember ever doing a water pump on a 903 except at overhaul, so it may be a difficult source. I do know that Cummins Mid Canada still supports the 903, even though you may be hard pressed to find a mechanic who has seen one. Good luck, being broke down anywhere is no fun.