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Old 25-07-2016, 07:18   #1
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Diesel engine losing revs

I have been having trouble with my Volvo Penta 2003 for the past 6 days. On Monday I sailed across Lake Erie in heavy seas ands high winds. when I arrive in Ohio, the engine stalled and wouldn't start. The next day a mechanic repaired an electrical problem - in fact, he bypassed a relay to get the boat to start. The engine would stall after just a few minutes of running. We found that the primary filter was full of gunk, so that was replaced and an additive to break up the remaining stuff in the tank was added. When I set off the next day, as soon as the boat was under load, it would lose revs when running at 2000 rpm or more, but would stay running. At under this amount of revs, the engine would stall which made docking tricky. I have checked the air vent to the tank and replaced both filters a couple more times and made sure that I replaced the gaskets at the same time.
My last stop I was able to run the engine in the marina for long periods of time, both at 2000 rpm and at idle without it stopping but once I got underway, I experienced the same problem of losing revs and stalling. The engine is definitely better than it was a few days ago. I am inclined to run the tank down to use up all the diesel in it and keep replacing the filters regularly but I wonder if others have experienced anything like this or have any other suggestions. I can't open the tank to look inside it.
The next stretch of my journey is the Erie Canal so I will be relying on the engine.

Any thoughts would be appreciated.

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Old 25-07-2016, 07:45   #2
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Re: Diesel engine losing revs

Similar thing happened to friend's boat, but it is an MD7A. We bled the injectors, and got the air out of both filters and now runs fine.

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Old 25-07-2016, 07:46   #3
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Re: Diesel engine losing revs

Call and have the fuel polished, it's good that you put the stuff in the fuel to kill the bugs, but now you will have to deal with dead bugs and there can be a lot of them.
How big a tank, how much fuel? It might be best to pump it all out and properly dispose of it, but there are usually fuel polishing services for just this reason. Many will tell you that you need to clean the inside of the tank, and if that is possible, you need to, but if it's not accessible, then you do the best that you can, but do get rid of that fuel or have it polished, I would not try the burn it out route unless there was no other way.
I would also use fuel additive from now on, I use Bio-bore, but there are several
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Old 25-07-2016, 16:59   #4
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Re: Diesel engine losing revs

Alot of tanks pickup tube have a screen at the bottom, this can get clogged also.

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Old 25-07-2016, 18:42   #5
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Re: Diesel engine losing revs

My first idea is if this is anyhow related to the drive train? Anything that simply slows the shaft down? Have you checked the prop, etc?

My other idea is I had a similar adventure when we had bad fuel - the engines (a cat) ran fine at low revs and at the dock, but once we were above 2400 in open water they would slow down and at times stop.

We chucked out all fuel, replaced all filters and took new fuel and we were off.

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Old 26-07-2016, 05:36   #6
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Re: Diesel engine losing revs

The rough weather mixed the gunk into the fuel. Some small particles are still in the fuel, killing the burning properties. Today's diesel isn't as hot burning as diesel was years ago. That's the reason we have soot problems with diesel stoves now. Anything that reduces burn quality throws off the fuel metering of the injector pump. You need more fuel for a given load with low quality diesel. A fuel catalyst will help you burn the fuel and clean your fuel system. I use Archoil AR6200 and also get 10% better fuel economy, too. I saw it on Jay Leno's Garage and first used it in my Ford truck. I drive a 3/4 ton 4x4 that now gets 25 mpg and no injector problems.
If you put a vacuum gauge between your primary filters and lift pump, you won't be changing filters just because you suspect them.
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Old 26-07-2016, 07:50   #7
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Re: Diesel engine losing revs

Thanks for all the responses. I don't think it's a drive train problem as initially the engine wouldn't even idle or run in neutral at all.

I will check to see if the marina where it currently sits or a nearby one provides the service to empty the tank. I will also use some of the fuel catalyst that was mentioned. Again, I'm not sure how easy it will be to check inside the tank to look at the intake etc.

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Old 26-07-2016, 08:42   #8
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Re: Diesel engine losing revs

How can you stop a diesel engine?
fuel starvation - you're looking at that, a suction gauge would help
drive train resistance - you've eliminated that
air getting into the fuel train - still a possibilty, but unlikely given the symptoms
air starvation - distant possibility
clogged injectors - not likely, or it wouldn't start.

So, a suction gauge as close to the lift pump as possible would be the really good way to monitor the situation after you clean the tank.

Consider flushing the tank with fresh fuel that you then recycle if you can't really get into it.
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Old 26-07-2016, 09:00   #9
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Re: Diesel engine losing revs

Hi I had the same problem with a Yanmar dirty diesel but problem is tanks pickup tube as Badsanta said. Take aut tanks pickup tube and clean
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Old 26-07-2016, 11:11   #10
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Re: Diesel engine losing revs

After you check out all of the above suggestions, It is wise to focus your thoughts on the fact that you have a BOSCH fuel system. I feel sure that you are aware that Volvo charge a fortune for parts. and injectors are a prime example. The Local Bosch Authorised dealer (Fred Holmes, Richmond, BC) were happy to rebuild all three On my Volvo 2003 for $456.60 cents. CDN. My engine would not even start before they did this. It was salvaged from another yacht and had 4,158 hours on it. it had been sitting for at least two years but possibly five.

Before the work was done they loaned me a small slide hammer made out of an old union nut that I had to connect onto the injector instead of the fuel line, Thus after the clamps were removed the injectors came out easily. At their work shop they took me out to the back of their shop and showed me their test bed. Only one of them showed any hint of mist. and all three of them gave out four streams of liquid fuel oil like a cross.

They cleaned out the injector bodies and replaced the working parts with new ones that had to be special ordered from Montreal, Quebec. After rebuilding they demonstrated the gaseous mist that should be produced. After replacing the injectors the engine that would not start, that previously would only produce thick smoke. fired in the second revolution and ran perfectly.

(it is good insurance to install a 'Suredrive' on your 2000 series Volvo before the MS2B drive spline fails completely)
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Old 26-07-2016, 11:23   #11
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Re: Diesel engine losing revs

Keep it simple, Its likely continued problems with your fuel system. Yes, the tank should be pumped and/or polished, in addition, the dip tubes should be pulled to ensure they are clear (including screens). Also, your primary fuel filter should be DISASSEMBLED and ensure they are clean. Naturally, your secondary fuel filters should also be replaced.

If you question your fuel tank, rig up a day tank (AFTER) you are certain your primary fuel filters are disassembled and clean. Racors have a tendency to trap and build up solids in the float ball which restricts fuel flow.

Happended to me... pain in the A**, but its a simple fix once you know what's going on. I have transition from Racor 500's to 900's to increase my filtering capacity.


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Old 26-07-2016, 14:30   #12
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Re: Diesel engine losing revs

Hi I am a diesel mechanic with a 50 year old boat ,I like my engine to run i like to have confidence that my engine will run even though nothing has been touched for 50 years only oil and filter changes ,it is a volvo .my advise to you is to fit a decontaminator filter before your ordinary filter this way you do not have to pay for diesel polishing and you can clean the gunk out as and when it occurs .these filters cost around 200 pounds order on line or watch their video on u tube fuel guard .This will give you peace of mind .I have worked on volvo 2003 engines great engine .If an air lock was your problem the engine would be very difficult to start but once started the air lock would vanish so not that .If the injectors were faulty you would have thick black smoke from un burnt diesel so not that .mechanical failure is unlikely but can be checked by running up the engine and loosening the 17 mm nuts on the injectors one at a time on each cylinder and listen for the revs to drop if they do not drop that cylinder is not working . most likely is blocked fuel filter and bad fuel .
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Old 26-07-2016, 15:17   #13
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Re: Diesel engine losing revs

I just had a similar issue with my Volvo Penta MD2030. I replaced the fuel injectors, feed lines, primary and secondary filters and polished the fuel. Engine started and idled OK but lost power at about 1500 rpm.

Something I haven't seen mentioned yet is your wet exhaust -

Mine was a bit grey so I collected a few cups of water to check it out. Carbon floated to the top ... I googled the symptoms and was pointed back to this forum. Apparently, the MD series notoriously gets a carbon build up in the wet exhaust exit elbow and stalls out the engine. I took the elbow and hoses apart and sure enough the elbow was clogged - as in carbon hardened into a brick with only enough room for a stream of water to pass. After a soak overnight and a good scrub with a bottle brush the engine sounds and runs better than ever. Cleaning the elbow is now on my yearly check list.

As a side note the Volvo elbow is cast iron and brittle. When I was cleaning it I actually chipped a piece of it off - nothing too serious - but I found a vendor in the UK that is aware of the flawed part and custom makes it out of 316 S/S. I ordered one as "preventative maintenance" which is in transit to me now.

Hope that helps!
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Old 26-07-2016, 16:30   #14
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Re: Diesel engine losing revs

Hi, been there done that, with my boat it turned out that the fuel lines themselves were partially blocked with crud from diesel bug.
The long term fix was to fit a sediment/water separator before the primary filter as close as possible to the tank and to use an additive to kill the bug and condition the fuel. This in addition to some basic fuel polishing solved all my problems, (touch wood)
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Old 26-07-2016, 18:31   #15
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Re: Diesel engine losing revs

I had similar problem with mw V P 2003 as well.
Had a small piece of slime caught in the pick up tube in the tank. Had to use air pressure to blow it back to the tank and then remove crud from tank

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