Volvo penta 2002 RPM failure

[ru2lph]

Hello everyone, first of all I would like to introduce myself,
My name is Rudolph and I am from Spain.
I have come to this forum looking for information for a problem that I have in the volvo penta 2002 of 18hp installed in my sailboat, a Fortuna 9, built in shipyards in Galicia (Spain).

The problem arises when when starting, and at low revs, the engine is not able to accelerate. sometimes it is necessary to stop by pulling the stop cable and start again by accelerating a little. then yes I get it to turn up the revolutions.
This problem arises especially when the shaft rotates, being less frequent if I try to accelerate without engaging the propeller.
I have adjusted the idle speed up a little up to 850rpm and although the problem seems to repeat itself less, there are times when the revolutions drop a lot until 500, and it is not able to raise rpm. other times, when lowering revs it stays accelerated over 1200rpm.

I have tried new diesel, there are no leaks, checked the feed pump and it remains the same. New filters for diesel I think it may be the fuel regulation system that contains springs and springs and something may have worn out or rusted.

I am trying to see some image or video of how to remove the throttle cap since in the exploded view it is not clear how to remove it.

Has anyone had a similar problem and have information about it?

Cheers

Rudolph

[MicHughV]

In past years I had the Volvo 2003 engine...there will usually be no simple answer.
start with checking all your fuel lines for blockage....check your fuel filter for blockage, check the fuel return line....check the condition of the fuel....check for debris in the fuel tank etc...
also check for air in the fuel lines.....
check the fuel pump to make sure it is delivering fuel...etc...

the fuel metering system for most diesel engines is an extremely tight tolerance device, it is not something you can check or fix yourself...you would have to take it off and send it somewhere.....but before that....remove the injector nozzles at the cylinder heads and take them in to be checked..

make sure every things is properly bled, all air removed...fuel lines, fuel pumps, fuel filters, etc...

[MicHughV]

I forgot to add...the fuel tank will have an air vent line, that exits the hull somewhere. sometimes, small wasps, etc, build a nest in there or salt spray, etc.... if that vent line is blocked it will interfere with fuel delivery.

[ru2lph]

I forget say that i revised the fuel tank Air vent and os OK

[Searles]

If the engine revs freely when out of gear ,check the drive gear ,has the g/box the correct type of oil and the correct amount ,can you turn the shaft by hand easily ,the idle of 850 is about right for these small engines if it still bogs down in engauged check the exhaust elbow for restrictions ,if ok it’s fuel problem ,check the outhers first ,I/e the easy ones . Good luck .⛵️⚓️👍

[Searles]

Just jogged my memory ,these engines have a cold start ,from memory out of gear advance to full throttle ,pull stop cable full travel ,push fully back in return throttle to approx 1/4 ,start ,should do it, check manual if possible ,.⛵️⚓️

[ru2lph]

Originally Posted by Searles

Just jogged my memory ,these engines have a cold start ,from memory out of gear advance to full throttle ,pull stop cable full travel ,push fully back in return throttle to approx 1/4 ,start ,should do it, check manual if possible ,.⛵️⚓️

Thank you for your help,
The gearbox IS a Saildrive 120S Volvo penta, It turn right when low rpm but It doesn't go .
When I try cold start It works ok, the engine always start very fast. But doesn't get revolutions If It fall to 500-600rpm when you put gear advance.

I have been thiking about engine mount. They are on bad condictions .
Could it be that excessive sideways movement at low rpm does not allow the counterweights to do their job?

I'm sorry for muy bad english.

Regards

Rudolf

[GordMay]

Greetings and welcome aboard the CF, Rudolph.

Volvo Penta Manuals & Handbooks, & Recall Information
➥ https://www.volvopenta.com/service-a...t/your-engine/

Workshop Manual ➥ https://ab-marineservice.com/wp-cont...SHOPMANUAL.pdf
➥ https://avdhoeff.home.xs4all.nl/zeil...hop-Manual.pdf

[ru2lph]

Originally Posted by GordMay

Greetings and welcome aboard the CF, Rudolph.

Volvo Penta Manuals & Handbooks, & Recall Information
➥ https://www.volvopenta.com/service-a...t/your-engine/

Workshop Manual ➥ https://ab-marineservice.com/wp-cont...SHOPMANUAL.pdf
➥ https://avdhoeff.home.xs4all.nl/zeil...hop-Manual.pdf

Thanks for the manuals.
I have been able to read it before, but it is not clear to me how to remove the cover from the throttle and stop lever.
It has 4 screws but I don't know if when I release them and open the cover I must be careful with something so that springs and springs do not come loose.
also, is it necessary before removing the 4 screws from the cover to unscrew the throttle and stop levers from the cover?

Greetings

[MicHughV]

I've owned two Volvo's...but as I've said before, you will likely have to start a process of elimination to find the problem.
I can't say whether the gearbox is the problem or not....Volvo does use this very unusual Cone clutch system. Mind went bad, and the gearbox would not go into reverse and I got a new one...but I could not....with the naked eye tell the difference from old to new.

My shoot from the hip diagnosis is that it is likely a fuel issue....I can relate one other story.... another boat I came across in the islands was having a similar issue....also a Volvo, but a bigger engine. In desperation to help the guy, I removed the fuel vent line so I could blow into it with my mouth, and had him open the filters, fuel pump, injector nozzles, etc, one thing at time, and let the fuel run out. Amazingly, we noted air bubbles at some locations. How they got there, I could not say. After this exercise, we tightened everything back up and the engine ran smooth as can be..

[MartinR]

Almost guaranteed an air leak in the fuel system. Maybe in the fuel return line if you can not find any other place. If there is air in this it might leak back through an injector.

[MicHughV]

my thinking exactly...an air leak somewhere

[ru2lph]

Thank you all for the answers.
It does look like an air leak in the fuel but we have checked everything thoroughly.
I even supplied new diesel from a clean carafe.
Do you think it could be air in the circuit? In that case, why when the engine is above 800rpm does it work well? The problem only happens when the engine is below 800rpm, for example after a cold start. when hot, the rpm ranges between 600 and 850rpm.

[MicHughV]

we are not there, so can't see what you are doing or have done...but diesels are relatively simple engines, they generally require only clean fuel and clean air, and an oil change at regular intervals.
you may think you have checked everything, but might have overlooked something.
purging the air out of a fuel line requires some forethought and attention, and it must be done in a specific way and sequence...ie, for instance,if you release the fuel line from the injector, you must keep the fuel pressure on while tightening it again....all the while making sure, there is no air....no bubbles....etc...also make sure there is no air in the fuel filter, often a common problem.
it might be worth your while to get a diesel mechanic out to the boat, that way you have an experienced set of eyes on the problem.
there is only so much you can by getting opinions on this site.

[ru2lph]

Trouble solved.
Piece n25 is K.O
Thank for all

Regards
Rudolf