Diesel Bug????

Russ the Diver

Russ the Diver

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I have twin engine Volvo pentas, D1-20
I have a problem with one engine whereby it drops power,
The marina says it could be diesel bug in the tank, wouldn't that affect my other engine?????
ta
Russ
 
My problem is this.
Had a great deal of work done on the starboard side engine as we had this problem at the start of the year. The yard did lots of work and over the season have had no problems, however on our last trip out before winterising, the engine started playing up with the same fault, the yard no wants to blame it on engine block,exhaust elbow?? lack of compression possibly?? all these they are guessing at. I've tried to bleed system through but keep getting air pockets through the pipe. The only difference I can think of is that the fuel tank is now half full and not full as it was when they looked at it?
 
Russ the Diver said:
but keep getting air pockets through the pipe. The only difference I can think of is that the fuel tank is now half full and not full as it was when they looked at it?
Click to expand...

Looks like you've found the cause and just need to find the cure...
I had a similar problem and I ended up changing all the seals in the fuel system.
 
Yes the problem is air in the system. This can be a simple matter of replacing the washer on the bleed srcew on top of the filter. Try this first. if not then it will a matter of working back and checking all seals and joints and jubilee clips.

Good luck
 
you could experiment with a long flexible fuel line bypassing the existing pipes and filters. maybe even starting from a Gerry can of clean fuel. I had to do this at sea once!!
 
tri39 said:
you could experiment with a long flexible fuel line bypassing the existing pipes and filters. maybe even starting from a Gerry can of clean fuel. I had to do this at sea once!!
Click to expand...
YES, thats the thing to try first - worked for us when we had water in the fuel, got back ok and then had to clean out the tank - we found quite a lot of water!
As said earlier, alsocheck for air leaks - we had this problem after 50hrs after fitting a new engine, got towed into a marina in Holland by a friendly dutchman. I had fitted a new tank and all new pipework but after tightening all the fittingsthe problem was cured!
 
If possible, swap the feed pipes over so the engine is running on the "good" supply. If the problem persists then you need to look at the pump and its filter and non return valve, secondary engine filter (if fitted) and fuel lines after the secondary filter to check for air leak.
 
Regarding Fuel bug... you really need to know that the sytem is clean. If not for the present problem then simple reliability of the boat. You need to drain off fuel from the bottom most point in the tank hopefully a deep sump that is lower than the engine fuel pick up point. You need to confirm that ther eis no water there. You need to do this test regularly like at least once per month. If there is any water as seen in a glass jar of the drained fule then keep draing till it is clean. If fuel is clean you can return the fuel to the tank.
You then need to use a bug inhibitor also regularly. Lastly check and examine fuel filters regularly for the tell tale signs of black gunge.
Yes probably an air leak in the fuel line as the present problem but sure as anything you will get diesel bug problems if you don't do anything . good luck olewill
 
Russ the Diver said:
Separate fuel lines and filters to both
Click to expand...

For an instant check swap the fuel lines round and you will have an instant diagnosis, ie if the other engine drops its the fuel supply, if it dosent its the engine.

Also get a mechanic to do a compression test on both engines, until you know what the compressions are a mechanic cant do a proper diagnosis, ok you can mess about with filters, cleaning the tanks etc but a compression test is like an ECG.
 
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just thought i would update you all. Firstly May I say thank you to you all that gave good advice and comments very helpful.
I have now filled the fuel tank to level it was at the beginning of the season. Have bled the system through with no air coming through. Which I believe will sort the problem/
I now need to find out if the fuel pick up for that engine is faulty in some way.
Will post my findings in due course.
 
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