Newbie Diesel Question

[jrd22]

I'm not very familiar with that model, but what is the idle RPM supposed to be? You said that it smoothes out at 1000, if I remember correctly isn't idle speed about 900 on that model? My Volvo MD31A (62hp) shakes and vibrates when it first starts and is below normal idle speed and then smoothes out. You should contact Volvo and get the idle setting, then check the RPM at the engine with a handheld tach, don't believe your tachometer until you verify that it's correct. It may just be that your idle is set too low. I had a Yanmar three cylinder that would shake pretty violently at low RPM when cold, but was fine after running for a minute or so.

[Rockter]

My own vibrates, a Volvo MD17C.
I just avoid the wobbly revs.
It's been like that for 15 years.

[Jotun]

Could it be that the shaft and engine flange are poorly aligned? Just a guess. I am far from an expert.

[davidpm]

Moonie:
Make sure you report back when you figure it out. It is nice to see the conclusion of these puzzles.

[SteveInMD]

If you have a small air leak in the fuel system often a diesel will idle poorly and run poorly at low rpm (misfire and shake). Once you throttle up it can greatly improve the performance. I'd guess a small air leak is by far the most likely cause of the shaking.

[badsanta]

Your idle speed may be too low and Your tachometer may be off. If you can find a laser revolution counter, It will tell you your true engine speed and then compare it to the engine tach. It may be off. And you may be to slow causing more vibration.

[bubb2]

I am not a Volvo mechanic, but I will relate to you what happen to me with my Yanmar. About the 3th year we owned the boat the Yanmar started shaking so bad at idle the whole rig would shake. It sounded terrible. What was wrong was the throttle cable has stretched and it was idling to slow, in fact it was firring only one cylinder. I made a adjustment on the cable, no more problem.