Hello all -
We have a Yanmar 4JH3E engine, installed in 2004 by the prior owners of Pelican. A few weeks ago we started having an issue with it - when you hit the start button, it slow cranks, almost sounding like there's a hydraulic lock, but you can still hear the piston sliding in the cylinder. We stop cranking after 3-4 seconds. We then wait a few minutes and try again. After 8-10 times, the engine will finally turn over, but it "winds up" to actually turning over - it's not like it used to be, starting up within a couple of seconds and immediately turning over, like a good diesel should.
We have a second issue, maybe related, maybe not, maybe a contributor, maybe not. The engine is rated for 4,000RPMs at full open throttle. The maximum we can push it to with the transmission engaged is 2,600-2,700RPM. If you go over 2,400RPM for any longer than 2-3 minutes, the engine overheats. With the transmission disengaged, you can push it to the full 4,000RPM. Obviously there's an issue with the prop - it's a Gori, so it's either not opening correctly or is overpitched. The prior owner seems to recall cruising RPMs being around 2,800-3,000, which is where they should be. I've never seen it at these RPMs. LET'S NOT FOCUS ON THIS ISSUE, BUT I WANTED TO PUT IT HERE JUST SO EVERYONE CAN GET ALL THE FACTS.
Here are a bunch of notes from various diagnostics we've done and some done by a very good diesel mechanic here in Charleston:
- Blew out the first starter by overcranking, so the starter was replaced 2 weeks ago with a brand new one.
- We get a little white smoke from the exhaust
- We get a small amount of unburnt diesel from the exhaust
- Both of the prior two items can be explained away due to the possible issue with the propeller
- No black smoke
- No blue smoke
- Slight moisture on oil fill cap. Still have to do oil change, but took some oil from dipstick, put it in foil, heated it and no crackle. Checked cap again today, no moisture.
- May be a SLIGHT sheen on coolant, but difficult to tell
- Did load test on battery and it was fine. Showed a weak ground on the engine, so regrounded directly to starter. Does not appear to be a problem with the switch - same issue occurs when bypassing the panel
All of this led us to check the mixing elbow:
- Thought there may be a carbon buildup in engine due to prop issue, so we pulled off exhaust elbow
- Good news - no carbon buildup
- Bad news - water came out, some sludge in there - obviously not a good thing
- Replaced the mixing elbow with a new one
- Unscrewed each injector nut and engine reacted properly
- Did compression test of cooling system and showed no pressure loss
- Have not done cylinder compression test - yet
- First time we started the engine after replacement it started right up - no delay, perfect start
- Turned on engine the next day, problem returned
- Ran the engine for 4 hours yesterday, checked mixing elbow today (12 hours later) and NO moisture.
A few more comments:
- When engine is running, very smooth - no misfires, no weird sounds - mechanic said it purred.
- Can restart engine easily if it's been running for a while, you turn it off, and then turn it back on
- Seems that any time you change something (i.e. starter, filter, reground, etc.) engine starts right up, then is back to its old tricks the next day.
So with all of that said, any thoughts? Our current thought is leaning towards the head gasket leaking - perhaps not fully blown, but on its way. I'm trying to figure out if there are any other things we can check before we take apart the engine.