Volvo MD17D revs issue

[Free as a Bird]

Hi all.
I am a new member from Australia. What a great find this site was.

I have an old Volvo MD17D which despite its age continues to run well.
However, it has one extremely annoying habit.
Once running, particularly at warmup, it will run happily at the revs set from the standard single lever power engine control, then for no apparent reason, either drop back to idle or race. It has always done this.
The mechanic who has serviced it and specialises in Volvos said he has never come across this before.
I am not very mechanically minded but can get by.
Can anyone offer any hints about how I can fix this?

Also, any other useful hints about this mid '70's engine would be welcome.

On a more general note, to reduce noise, just how enclosed can you make Diesel engine compartments? Is heat build up an issue?

Pete. Adelaide, Australia.

[Navatech]

Originally Posted by Free as a Bird

Can anyone offer any hints about how I can fix this?

I'm not familiar with this engine but possibly you could find an answer on boat diesel.com.

Originally Posted by Free as a Bird

Also, any other useful hints about this mid '70's engine would be welcome.

Again, boat diesel.com should have a lot of information for you.

Disclaimer, other then me being a satisfied user and occasional contributor I have no connection to the boat diesel.com site.

[Free as a Bird]

Thanks. Have joined.

[Sandero]

I have the same engine... for 28 yrs and it runs well. It does seem to have a rpm issue until it warms up... tends to creep up in revs as it warms up.. which is not an issue if one is motoring such as leaving the dock of anchorage as YOU control rpms based on need of propulsion. Mine kicks out a bit of smoke on cold start and that disappears as it warms up to no smoke. I think that normal.

I've also found that once up to operating temps its idle is very low... perhaps 800 and a bit rough and so I tend to idle it a bit higher in neutral. The tach is hardly accurate or precise.

I don't know much about diesels but this one seems to have a pretty simple system re supplying fuel ergo determining rpms.... no electronic feedbacks, for example. I just assumed the mechanical connections ... teleflex, levers, springs and so forth seem to have their own comfortable places. I can't comprehend how the rpms would rise a lot without some mechanical setting moving on their own.

This seems to be where it happens! Not much there there.

What do I know?

Noise is an anoyance... Ain't it? If you don't have set up a blower to draw air out of the engine compartment to overboard. The engine room should not be completely sealed and so cooler air is drawn in... for combustion as well.

Use lead faced foam sheets on the walls. Helps a bit. But it does get hot in there and diesels like to be hot. Watch your temp gauge. You don't want to let it get too hot from clogged cooling hoses, pipes or a busted impellor.

[Free as a Bird]

Thanks defjef. Yes she is noisy mother. I have used good quality sound absorbing material but have to reduce the noise more.
A blower is a good idea.
You only need a tiny opening to let through an enormous amount of noise.
I agree that you can't totally enclose the compartment.
Boatdiesel.com has a post which gives a recommendation as to how much ventilation you need per horsepower.

[Sandero]

I have a 3" Ø port for the exhaust blower at the rear of the compartment. The air is pulled in from the cracks of the enclosure panels and through an opening just above the shaft exist in the aft section which is where the exhaust hose and so forth pass. It's less than .5 sq sf. I use a inline blower which comes on when the ignition key is turned on... regardless if the motor has started.

The motor is noisy... and the lead coated foam insulation does not block most of the noise. I'm used to it now and so I hardly notice it.

Noise is not necessarily bad.. once you learn the sound... and can tell is something is off.