Wondering if anyone has had a problem similar to mine with a stubborn
diesel who might give some advice. The diesel is a two-cylinder Volvo
MD-7A. The problem (hopefully minor) is that when I start the engine, it
cranks up on only one cylinder and runs in the ka-thump, ka-thump manner
for two or three minutes before the second cylinder fires. In the interim, the
engine has no power and moving the throttle forward accomplishes nothing.
A local diesel mechanic comments only "tired engine" and hints at a
compression problem when I mention this but has not examined the engine
closely. Once the second cylinder fires off, everything runs fine, for hours if
needed. There is no black smoke from the exhaust at any time. Could there
be an injector/fuel glitch in the stubborn cylinder, or is this a sign that the
engine might need an overhaul? I can live with the problem for awhile but this
could spell trouble if I had to fire up the engine for immediate use in an
emergency. All thoughts appreciated. Thanks.
joebrown@mint.net
Fussy Diesel
Moderator: Jim Walsh
-
Barry
Re: Fussy Diesel
Possibly a sticky valve (frees up when the engine starts to get warm). Pull the rocker box covers and see if the valves are returning -- Marvels Mystery oil may help. My next thought would be to pop test the injectors.
Barry
CD-33
Barry
CD-33
-
Larry DeMers
Re: Fussy Diesel
Sounds very familiar. Do a fuel system bleed on the low pressure side until the fuel is clear of all bubbles and foam. The place to do the bleeding is on top of the secondary fuel filter (mounted on the engines front..silver, filter screws into the filter cap, which has the bleed screw on it's top.
Next, bleed the high pressure side at the injectors. To do this, have someone standby the start switch and throttle, while you gather some paper towels, and arrange them around the base of the back injector.
Either remove the water drain bolt in the bottom of the water lift muffler, to allow the water being pumped by the engines cooling system to exit the muffler body (so that it will not accumulate and flow back into the engines exhaust, flooding the engine. Or.. simply turn the water inlet seacock to a partialy open or even closed position (this is what I use..Nitrile water impellors will run dry for hours without a problem).
Raise the compression release lever up fully. Place a wrench on the injector nut and lossen it slightly while the assistant opens the throttle fuly and turns the engine over. Loosen the injector nut more, until the fuel begins to leak out. Continue for no longer than 30 sec. without a rest for cooling the alt. (no engine load makes this just precautionary). Watch the fuel flow, and when there are no more bubbles or foam coming out, close the injector nut..while the engine is turning over.
Repeat for the forward cylinder.
It sounds to me like an air blockage in one cylinder. The CAV or Bosch Inj. Pumps are self-purging to an extent, and they accomplish this after the other cylinder starts up..yours takes several minutes..mine took 30-60 sec. Depends on temp. and engine condition. You have a leak somewhere in the high pressure system, probably in either pipe from the pump to the injector fitting. The seal of these pipes must be perfect, or they will leak air. Check each nut (I know..there is no room at all. But you can reach it from the back of the engine if you are small and lucky enough to get in there. Otherwise, it's like I do..mirrors, fixed lights everywhere in that compartment, and the removal of the muffler body to allow me better reach. It comes off easily.
The other suggestions are good too, and should be considered after you have an airless fuel system, but still have the problem.
We ended up rebuilding our engine 4 years ago, and it cost $2500 at that time. Parts are much higher now, and the current cost for the same place is $5400...and you bring the engine. He has 9 lined up to do this winter..all makes and sizes. It was well worth it, and we now have that reliability you talked about, with a quick starting adn powerful engine.
Incidently, you guys can do your MD7A/B some good by getting a load of Deep Red Colored Diesel fuel..Off Road Fuel is what they call it in Michigan and Wisconsin. It is higher sulpher content, is legal for off road vehicles and trucks. Boats are sure as heck 'off road' vehicles, although my interpretation may not be what Washington intended..
You will notice a bit more smoke at first, the engine will have a deeper tone to it, there is more power, and it feels like you grew 2-3 extra HP (not bad with a nominal 13 hp to start). It seems to have a lasting effect, after you return to the yellow colored low sulphur fuel.
Sorry to ramble so..we're puttin our boat away this weekend..and I am already in the withdrawls I see. 'Tis a long winter.
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~~~Sailing Lake Superior~~~~
demers@sgi.com
Next, bleed the high pressure side at the injectors. To do this, have someone standby the start switch and throttle, while you gather some paper towels, and arrange them around the base of the back injector.
Either remove the water drain bolt in the bottom of the water lift muffler, to allow the water being pumped by the engines cooling system to exit the muffler body (so that it will not accumulate and flow back into the engines exhaust, flooding the engine. Or.. simply turn the water inlet seacock to a partialy open or even closed position (this is what I use..Nitrile water impellors will run dry for hours without a problem).
Raise the compression release lever up fully. Place a wrench on the injector nut and lossen it slightly while the assistant opens the throttle fuly and turns the engine over. Loosen the injector nut more, until the fuel begins to leak out. Continue for no longer than 30 sec. without a rest for cooling the alt. (no engine load makes this just precautionary). Watch the fuel flow, and when there are no more bubbles or foam coming out, close the injector nut..while the engine is turning over.
Repeat for the forward cylinder.
It sounds to me like an air blockage in one cylinder. The CAV or Bosch Inj. Pumps are self-purging to an extent, and they accomplish this after the other cylinder starts up..yours takes several minutes..mine took 30-60 sec. Depends on temp. and engine condition. You have a leak somewhere in the high pressure system, probably in either pipe from the pump to the injector fitting. The seal of these pipes must be perfect, or they will leak air. Check each nut (I know..there is no room at all. But you can reach it from the back of the engine if you are small and lucky enough to get in there. Otherwise, it's like I do..mirrors, fixed lights everywhere in that compartment, and the removal of the muffler body to allow me better reach. It comes off easily.
The other suggestions are good too, and should be considered after you have an airless fuel system, but still have the problem.
We ended up rebuilding our engine 4 years ago, and it cost $2500 at that time. Parts are much higher now, and the current cost for the same place is $5400...and you bring the engine. He has 9 lined up to do this winter..all makes and sizes. It was well worth it, and we now have that reliability you talked about, with a quick starting adn powerful engine.
Incidently, you guys can do your MD7A/B some good by getting a load of Deep Red Colored Diesel fuel..Off Road Fuel is what they call it in Michigan and Wisconsin. It is higher sulpher content, is legal for off road vehicles and trucks. Boats are sure as heck 'off road' vehicles, although my interpretation may not be what Washington intended..
You will notice a bit more smoke at first, the engine will have a deeper tone to it, there is more power, and it feels like you grew 2-3 extra HP (not bad with a nominal 13 hp to start). It seems to have a lasting effect, after you return to the yellow colored low sulphur fuel.
Sorry to ramble so..we're puttin our boat away this weekend..and I am already in the withdrawls I see. 'Tis a long winter.
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~~~Sailing Lake Superior~~~~
Joe Brown wrote: Wondering if anyone has had a problem similar to mine with a stubborn
diesel who might give some advice. The diesel is a two-cylinder Volvo
MD-7A. The problem (hopefully minor) is that when I start the engine, it
cranks up on only one cylinder and runs in the ka-thump, ka-thump manner
for two or three minutes before the second cylinder fires. In the interim, the
engine has no power and moving the throttle forward accomplishes nothing.
A local diesel mechanic comments only "tired engine" and hints at a
compression problem when I mention this but has not examined the engine
closely. Once the second cylinder fires off, everything runs fine, for hours if
needed. There is no black smoke from the exhaust at any time. Could there
be an injector/fuel glitch in the stubborn cylinder, or is this a sign that the
engine might need an overhaul? I can live with the problem for awhile but this
could spell trouble if I had to fire up the engine for immediate use in an
emergency. All thoughts appreciated. Thanks.
demers@sgi.com