Volvo diesel engine problem

Kamahele

Seaman Apprentice
Joined
Oct 12, 2013
Messages
36
My boat has a Volvo Penta MD2040 engine. Starts Ok but after running about 30 minutes revs start to fluctuate a couple thousand revs (1800-1600 rpm). After about an hour it can't run at low revs and stalls at idle (sometimes the warning alarm goes off when that happens). Engine heat normal, not overheating. If engine cools down for about an hour runs OK, but after a while problem starts again. A mechanic has changed the fuel filter and tested that enough fuel is getting to the engine. Says that the fuel tank needs cleaning. I'm reluctant to go through that if something simpler can be done. Wouldn't a dirty fuel tank make the motor sputter? I don't understand the logic of how the problem occurs after the engine has been running OK for a while. Any advice?
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
It's possible that trash in the tank can gradually block the pickup screen until not enough fuel can be delivered. When the motor rests for an hour, the trash falls off the screen waiting to be picked up again.

Was the fuel filter cut open or examined for junk?

Has the fuel pressure been tested during the fluxing revs? I would consider that sputtering.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
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47,297
Agree with GA. Pull fuel filter and cut apart. Get the furl sampled for biological contamination (algae).

Marine diesel tanks often need cleaning
 

Kamahele

Seaman Apprentice
Joined
Oct 12, 2013
Messages
36
Thanks GA and Scott, good explanation of crud in tank. Fuel filter was not examined when changed. I'll try to get fuel pressure tested. What can be done if there's bugs in the tank? Does tank have to be removed to clean?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
47,297
guaranteed there is a local fuel polishing service that comes to your marina. I guarantee that if it is fuel issues, you are not the only one in your marina with them.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Sounds like a diesel bug, water in fuel problem or both.
Suck all the fuel out and replace. You'll probably find that your mechanic is right or not far off.
If your lucky you will be able to suck it all out using a vacuum pump like the Ines used to suck oil out the dipstick on your engine.
 
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