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Old 09-01-2020, 23:03   #16
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Join Date: Nov 2013
Location: Slidell, La.
Boat: Morgan Classic 33
Posts: 2,684
Re: Why my MD7a doing this?

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Originally Posted by metacentre View Post
Hello Everyone!

It is fixed thanks to you all!
It was the clogged tank sucking line! System was trying to suck the fuel and getting air from the water separator inlet as it is the weakest in my system.

I made a plan and went onboard today and went inside the small hatch on the port side and took the suction line out from the tank.
As soon as I took it off, black jelly dirt came out then I took my hand pump and connected and started to suck a lot.
It is like a ketchup first small pieces then more and boom big dirt came out. Then clean fuel started to come.
I connected everything, did bleed the system and now working better than ever.

Once again thanks one more time I learned that always start with the simplest and cheapest one 
Yeah, that big dirt can cause problems...

Though it might also cause some 'problems' at first (i.e. frequent primary filter changes), a good diesel biocide might be a good idea.

Don't waste your money on cheap 'additives' though, you want something like Biobor or Biokleen to get the job done.
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Old 10-01-2020, 00:25   #17
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Join Date: Sep 2014
Location: Auckland, NZ
Boat: Compass 790 , 7.9 metres or 26 ft
Posts: 2,542
Re: Why my MD7a doing this?

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Originally Posted by DougR View Post
Yes, the Bosch VE pump has an internal governor, and it may be that the governor is not controlling the fuel supply adequately.

But as stated earlier, feed the fuel from an independent source and eliminate any possibility of fuel starvation/ air in the system.

To me it almost sounds like the governor reacting to intermittent fuel supply, over reacting to the rpm loss, and subsequently dying from fuel loss.
Only after ruling out starvation have the injection pump checked.

DougR
I'd say this diagnosis proved to be spot on
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Old 10-01-2020, 13:16   #18
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Join Date: Jan 2020
Location: Rotterdam / the Netherlands
Boat: Albin Vega 27
Posts: 3
Re: Why my MD7a doing this?

Quote:
Originally Posted by Compass790 View Post
Glad for you it turned out to be the most common problem. Also very lucky you didnt have to go to the green engine shop for parts.
A further tip is always use a filter funnel when filling your tank & keep the o-ring on the deck fill cap in good condition.I'm amazed how much crap comes in the fuel from the pump & we buy diesel from a very busy auto fuel site. Sounds like you need a good tank clean.
Also glad you reported back.
Yes a good tank clean is on my to do list! Thanks!
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Old 11-01-2020, 17:45   #19
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Join Date: Jan 2019
Boat: Beneteau 432, C&C Landfall 42, Roberts Offshore 38
Posts: 2,857
Re: Why my MD7a doing this?

..I had an MD7B on my first boat, which I later swapped out for a 2003 series.
In the process I also removed the old fuel tank and on a whim opened the inspection hatches on top of the tank allowing me a view inside.

Was I ever amazed. The bottom and sides of the tank was covered in a dark colored heavy disgusting-looking slime. It was a good thing, my main fuel pick up line was 1.5" (37 mm) or so off the bottom of the tank, as I would have been sucking this stuff up all day long.

The MD7 series engine is no longer made, mine was installed 'round about 1980 or so, so if your boat has this engine, it is highly likely that it ( and the tank" was likely installed 40 some years ago.

My suggestion would be, even though the engine is running fine now, to have the fuel and tank cleaned. Testing the engine, while the boat is in a slip does not replicate the movement of the boat at sea, when you ( and the tank) will likely be bouncing around, stirring up all sorts of goop in the tank.

It doesn't help to have clean filters if the main intake line gets clogged up from tank residue.

While I'm at it. The MD7 series engines were raw water cooled. This would be a good time to remove the cylinder head, inspect and ream out the water cooling passages.
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