volvo 2003

cagey

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evening O wise ones,
following launch and normal niggles I ran engine to check for probs after top end overhaul, ran for about 1 hour under varying loads keeping eye on overheating and oil etc she ran nicely and I felt happy, huge mistake, the following happened;
1 revs dropped slightly and momentarilly [heard it]
2 revs returned to normal [perhaps 1 was imagination]
3 within 5 mins 1+ 2 very pronounced shut down did checks etc all ok start again 1+2 worse now engine seems to be labouring. No bad noises no steam no overheating stop engine rotate by hand all ok
4 symptoms are like heavy load not diesel probs
5 run her up revs freely and no noises just this labouring
6 noticed rev counter fed from alt is working intermitently
7 voltmeter went off scale
8 B--gg-r this engine off me on pbo forum
am convinced its not mechanical or diesel
any ideas
thanks
keith
 

jerryat

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Hi cagey,

Do you have a high output alternator? It's difficult to judge by just how much the engine revs are varying, but if the rev counter is also varying (as you'd expect) perhaps the alternator drive/fan belt is slipping due to a high demand for power.

This might apply particularly if your battery banks are discharged.

Otherwise, probably fuel problem, either dirty filter(s) or air being drawn into the supply line.

Cheers Jerry
 

BobOwen

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Can you remove the alternator belt and run the engine?

This would prove if the problem is with alternator load or not.
 

cagey

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ordinary 50amp alt, all batteries full [just launched]
can only run engine short time with alt disconnected as it is fresh water cooled and pump run by belt
pretty certain not a diesel prob symptoms and sounds not same also allfilters new and every thing serviced
 

andy_wilson

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Symptoms accurately reflect what would happen with a slight leak on the suction side of the fuel supply, i.e. drawing air in with fuel prior to engine pump, and likely around or after water-separator.

Check all connections, bleed, and try again.
 

cagey

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true but doesnt explain erratic behaviour of rev counter and voltmeter,
I have thoroughly checked diesel lines but will again although it ran for an hour before acting strange. The symptoms are not missing or hunting more like a load being applied
thanks for help
 

ShipsWoofy

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Your alternator sensed tacho may have problems with full batteries, it needs the charging circuit to be in operation to function. Without a potential across the battery it may be erratic.

It does say that in the blurb for mine.

Just a thought
 

brianhumber

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Over the years I have wasted many an hour trying to identify single faults when one or more were combined to kid me in looking elswhere.

Fuel leaks and alternator would seem to be the areas for you to check over based on your description.
 

boatmike

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Sounds like an alternator problem to me. One way to check is to take most of the tension off the drive belt. It will still run the pump but the alternator belt will slip if it's overloading allowing the engine to run normally. A bit unkind to the belt and pulley of course but a simple enough thing to do....
 
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