Hi all, my 3gm30 is difficult to start when cold or just not run for awhile. Takes alot of throttle to get it going and then it smokes quite a bit for approx. 5-10 secs. Then it runs great. Thoughts? Injectors?
Thanks, Dave M.
You've given a pretty fair description of the pretty common problem of low compression caused by weak or dry rings. While valves and head gaskets and the like can also contribute to low compression, those components are not lubricated by the copious fuel you dump on them by opening the throttle. Eventually, you get enough oil (in this case, diesel oil instead of lube oil) to seal the rings sufficiently to boost the compression sufficiently to raise the temperature sufficiently to auto-ignite the fuel and she runs. Then she smokes, burning off the excess fuel.
Simplest solution: exercise the engine more often, keeping the rings lubricated and the compression high.
Permanent solution: pull her down and replace the rings, and everything else you find getting there (note, you're doing a total rebuild at this point).
And there are about a dozen other intermediate solutions between the extremes, but that takes up lots of discussion space.
Had similar problem in same engine model. After standing (for days, not hours), motor was difficult to start, would fire on one cylinder and eventually run on all three with wide throttle. Clouds of white "smoke" were fumes of unburnt diesel, I believe.
It turned out the problem was air leaking into the tank-side hose connection to the lift pump. This hose connection is made on a short barb at a tricky angle. I made the connection sound, bled the system and the problem has gone completely! Even after standing for weeks, the start is first time every time!
Not long after solving this, Nigel Calder identified fuel air leaks as a possible cause of difficult starting in diesels.
My suggestion: check all fuel hose connections and other points in the fuel delivery system where air could leak (washers under bleed screws, seating of the fuel filter body on the motor etc). Bleed the system and hope it's that simple (and zero cost). Paul D.
Interesting to see that this starting / smoking issue is not so uncommon. I suspected that the lack of initial lube on the cylinder walls could be the problem and tried a heavier viscosity oil but that did not resolve the problem. I will also check for possible air leaks in the fuel line. Although I can see how a small amount of air could cause difficult starting I don't see how that is connected to the initial blast of smoke when staring the engine cold.
I have a similar hard starting problem, but once it runs and is shut down it will re-start immediately.
From the previous responses, this seems like a different problem.