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post #11 of 32 Old 07-31-2014
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Re: Volvo Penta MD6b Cold Start System

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..... I also see a lot of unburned diesel out the exhaust.
Scott, that says to me that you don't have a fuel delivery issue and it's more likely to be either (a) low compression or (a) fouled injectors.

I'd suggest getting the local marine service place to check the compression.

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post #12 of 32 Old 08-04-2014
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Re: Volvo Penta MD6b Cold Start System

I have an MD7A. I get the best cold engine starting results with the throttle wide open. Once it starts, bring the idle back to slow idle. Don't want to run a cold engine wide open. Before I discovered this starting technique, the engine would take forever to finally start. I'm pretty sure the manual recommends a wide open throttle at start. Try it next time.
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Re: Volvo Penta MD6b Cold Start System

I will definitely try that. I can report that she starts immediately with starting fluid.
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Re: Volvo Penta MD6b Cold Start System

Classic 30 - I think you are right , I would not have unburned fuel if no fuel was getting to the cylinders. I would not be surprised if it was low compression after 37 years. That also may be why the new starter that spun so much faster got her started right away too,

is it possible to throw the decompression lever while cranking with the electric starter ? maybe I could get her spinning faster and then flip the lever and she might start more easily.

Another thing I suppose I could check would be the valve clearances. They likely have never been checked or adjusted.

I was told by a mechanic ( whose opinion I trust ) that removing the injectors to is to be avoided at all costs as they likely have not been moved in decades and will likely not go back in without replacing the sleeves they are in , which must be done with the cylinder head on the bench. I know I can turn the engine over fairly easily by hand using the flywheel , but the flywheel is pretty large diameter. That could also be a symptom of valveses not adjusted to close all the way ?
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post #15 of 32 Old 08-05-2014
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Re: Volvo Penta MD6b Cold Start System

Hmm... I'm a tad surprised to hear removing the injectors is such a big deal, but if the engine runs ok (doesn't blow copious amounts of smoke) once it IS running, then that is probably not the first place to go.

Checking valve clearances should be relatively easy and would be worth doing given the age of the engine and the symptoms you have.

..and, yes, start with the throttle wide open and be ready to throttle back when it fires.

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Last edited by Classic30; 08-05-2014 at 12:45 AM.
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Re: Volvo Penta MD6b Cold Start System

Yes , that is what the mechanic felt- if it ran ok once started ( and it does ) then the injectors must be functioning properly. However that means I do not have compression information.

I can check the valves , to ensure they are closed when they should be - and I am going to try to figure out how to check the injector timing. I can't find the flywheel mark referenced in the service manual. and I still have not learned how the cold start system is supposed to work , because she starts up immediately when warm also.

She starts immediately on starting fluid- I think if the fuel lines had bled down while sitting it would take more work to get her running. So it seems there is fuel immediately.
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Re: Volvo Penta MD6b Cold Start System

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Yes , that is what the mechanic felt- if it ran ok once started ( and it does ) then the injectors must be functioning properly. However that means I do not have compression information.

I can check the valves , to ensure they are closed when they should be - and I am going to try to figure out how to check the injector timing. I can't find the flywheel mark referenced in the service manual. and I still have not learned how the cold start system is supposed to work , because she starts up immediately when warm also.

She starts immediately on starting fluid- I think if the fuel lines had bled down while sitting it would take more work to get her running. So it seems there is fuel immediately.
If your engine has pre-combustion chambers I have read ether can do heap big damage. I used it once, just a small whiff, on my VW diesel in 15 below Fahrenheit weather & it worked. I used to use it all the time on my Detroit 3-71 diesel, which was direct injected with no glow plugs, & it worked fine, starting in just a few turns.


Starting fluid - Wikipedia, the free encyclopedia

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Re: Volvo Penta MD6b Cold Start System

Scott...be careful when using starting fluid with the MD6 or 7 engine with only compression start...you can do damage to the engine if you use it too much as the ether "explodes" in the cylinders at a much higher pressure than the fuel. I have found that mine starts pretty well if I push the throttle to full and once it catches, back it down to idle...and mine is just a year younger than yours...I usually end up cranking for about 15 to 20 seconds, then back off for about 10 seconds...then on the second crank it usually starts up within 5 or 10 seconds...This engine is a cold hearted beast, but will run forever if you treat it right.
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Re: Volvo Penta MD6b Cold Start System

According to my engine manual the cold start set on my volvo 2003t is pull out the engine stop and push back in. This actuates a cam in the governor and kind of acts like a choke. Then set throttle to full, in neutral, and turn over. Be ready to idle back. The engine starts immediately. Until I read this technique my motor was very hard starting.
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Last edited by jimrafford; 08-05-2014 at 08:33 PM.
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post #20 of 32 Old 08-05-2014
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Re: Volvo Penta MD6b Cold Start System

Wow, you guts are making me feel VERY lucky. My MD7a always starts very easily. It was out of the boat under a tarp all winter. I pumped up the lift pump. Threw the decompression lever and cranked her for 3 or 4 20 second sputs. Then closed the compression lever and did the same thing. On the third go she fired up. Ran rough and died a couple of times as the air worked through.

Once, last summer, I had a devil of a time getting her going. No idea why other than I must have run out of fuel as I docked. Yeah, it was THAT close. Other than that she will crank up almost immediately, even after a 10 month lay up.

I've never had to run the throttle up much at all.

Guess I'm a lucky guy.
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