Adjusting Volvo MD2030 timing.

[adl]

I had a mechanic on board during the week over looking the service I had done.

On start up he commented that while idling the engine was labouring and that it was not at the correct rpm. Now I have the manual on how to adjust the engine speed but I assume this relies on the tacho being correct.

Do you use a light gun on the white spot on the crack end to check the speed like on a petol engine or is another method used?

Cheers in advance!

Interesting sail today in the solent, sun, rain, sleet and hail!

 

[ksutton]

Engine timing and rpm are not the same thing, you don't need to consider the timing reference point. If the engine physically looks and feels to be idling slowly and your boat rpm gauge is showing less than the manual says, then you should be able to trust your boat gauge. Increase the rpm a little at a time until the boat rpm gauge shows the manual recommendation.

 

[adl]

Thats the thing, the tacho is virtually spot on to within 100 rpm, I thought it would have to be more off?

Confused!

 

[ksutton]

100 rpm slow on a diesel at idle can make a lot of difference, even 50 rpm can make the difference between a nice smooth idle and a rough idle. If you are sure that the engine is running correctly on all cylinders, it will do no harm to lift the rpm by about 50 rpm and see if it smooths the idle out. Its not abnormal that after a few hundred hours to have to increase the idle speed a bit.

 

[tillergirl]

Mr Volvo manual says

"the idling speed shoud be 850 rpm + or - 25. If necessary, the idling speed can be adjusted when the engine is hot as foillows:

1. Put the engine control in neutral. Check that the gap twix (my word) between the inside of the nut at the end of the throttle cable and the adjacent block is approx 3mm. If not adjust until correct. Start enging and let it idel with engine control in neutral. Undo the locknut on the adjusting screw and adjust the screw to the correct speed. Tighten locknut and check value of first measurement. Do not adjust idel speed above that specified or unnecessary high stresses will occur on geear changes.

 

[adl]

Ok then, assuming I had no tacho how would I measure the rpm?
From memory when it is idling at 850-900 rpm. So it should be fine.

We had the engine on for 4 hrs yesterday and was running fine when loaded.

 

[ksutton]

Alex

If you doubt the accuracy of your onboard tachometer the option is to purchase an optical hand held tachometer, which you point at a reference point on the crankshaft pulley, as would be used by an engine mechanic. These are not cheap and unless its being used very regularly, would be overkill as far as your "suspected" problem is concerned. Looking at your comments again, I don't think your tachometer could be that wrong, and would go back to your mechanics original comment that the engine "seems" to be labouring at idle. Does it show this symptom all of the time, (when at normal temperature)? or is the labouring symptom worse immediately after the throttle is returned to neutral after being run at speed?. This would be noticeable by the tacho needle momentarily dropping below normal idle speed as the throttle is pulled back, (engine shakes a bit), but then picks back up to normal idle speed within a couple of seconds? Again this may be fixable by tweaking the idle adjustment just a little, but might just point to a fuel pump governor malfunction, if tweaking the idle speed doesn't cure it. The danger of having too high an idle speed would be premature wear on the gearbox forward and reverse clutches. However you can usually sense something is not quite right when selecting forward or reverse, as gear engagement may not not be smooth and may "clonk" as it engages. Also make sure that your gear selector is returning the gearbox selector (cleanly) back to neutral, if its not, then you could have a partially dragging gear engagement clutch, which may show itself as labouring the engine at idle.

Ken

 

[wotayottie]

If the engine is working well under load and seems OK to you at idle, I'd be inclined to ignore the mechanic. We all have the need to say something when asked "what do you think" and from my experience its just as likely to be nonsense as useful info.

Mechanics vary from the sort of engineer who fettles F1 cars to the lad who wielded a spanner in the local garage cos he was too dim to do anything else. Where in that spectrum is yours?

 

[adl]

Well the chap in question is a Director of a fairly large marine engine servicing and installation place in Southampton.

In reply to a question earlier when the engine had been run for a while it will quite happily sit at idle with out the oil pressure warning going off?