I have a question about a Cat 3116 in a wheel loader. If the engine has been run within a few days, it starts instantly from cold or warm. If it has sat for more than a few days, it takes 5 to 10 seconds to start; grey smoke and a few hits and then a few hits more and so on until it runs on six cylinders. I'm a noobie to Cat mechanical unit injector engines. Is the hard starting any indication of the condition of the injectors? The grey smoke makes me think that the fuel supply to the injectors is OK. Forty five hundred hours on the engine, all of the filters are new and there's nothing in the old ones, no metal or water or gunk. The engine runs good after it has started.
Sounds like the fuel is draining off to tank? Is there a priming pump and have you tried giving it a few strokes before starting?
It could be the start of an injector seat leaking. These injectors seat into a brass cup and when they start to leak they will let air into the fuel rail. It could also be a check valve leaking in the transfer pump. The transfer pump is located in the governor on these engines and has 3 plastic check valves. There is also a check valve in the return line at the front of the head. Do a fuel pressure check at the secondary filter and you should see about 20 psi at idle and 55 at full throttle. You can also put a clear line on the return fuel line to check for air in the fuel when running which would be an injector seat problem .
Putting clear plastic hose in the return line is something I can handle, and looking at the fluid in the hose. It will take me a couple of days to do that; I'll post the result. Thanks!