MD7A Volvo Penta Timing Gear - SailNet Community

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  #1  
Old 07-21-2008
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Question MD7A Volvo Penta Timing Gear

I have a MD7A Volvo Penta in my 1978 Newport Mark II. We just got finish rebuilding the whole engine and it takes quiet a few turns before it fires up. Some one who works on Volvo Pentas a lot said "he thinks" this motors timing gear is supposed to be a couple teeth off. When we took it apart we noticed that it was a couple teeth off and thought that the last person who put it together made a mistake. This is before the person told us "he thinks" .So, we put it together the way the manual said to line up the teeth, which is number to number.

I have called numerous people, sent volvo an email (with no reply) and called some parts houses. No one has heard of this. At this point it is just a rumor. Before we go back in to the engine it would be good to know if this is true or not.

Does any one have any information on this?

Mike
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Old 10-26-2008
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Comments on Timing Question vs starting ???

OK... if I understand correctly just rebuilt it but takes a few turns to start... couple teeth off really shouldn't have anything to do with it to my way of thinking. I just got a MD7A that was submerged for a week, and then sat for a month with the crank case full of water (good actually, no O2 available to start rust) and am in the process of tearing down as it sank while it was running. Might have bent a rod when it hydro'd. So I'm opening it up to totally clean up everything and inspect. Point is I've been inside alot of engines and have been for almost 40 years.... the observation you made makes some sense on a brand new engine. Remember, on a new or fresh rebuilt, the rings and cylinders are not broke in yet and as such can act like it has bad compression. Low compression on a diesel can start harder until the oil pressure created while cranking has lubed the cylinders enough to fill the micro groves left from honing. Especially if its cranking slow by being stiff yet. Once the rings are seated and the micro groves worn and sealed the compression will be much higher. This post is a little old so maybe its remedied itself by now.

The timing of a tooth or two either way on the valve train should not effect starting... I'd set it to factory spec and leave it.


Dave

Last edited by dem45133; 10-26-2008 at 04:33 PM. Reason: wrong word
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Old 10-26-2008
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I just bought an Islander 30 two months ago. I has an MD7A diesel also. I thought it was hard starting too. I talked to the Volvo rep at the Annapolis boat show earlier this month. He said to start it at half throttle and back off once it fires up. I tried that and it starts in about 10 seconds instead of 30 to 40.
Ron
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Old 10-27-2008
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Guys, depending on the size of the gear wheel, two teeth off could be quite an error. I take it that this is the camshaft gear?
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Old 10-27-2008
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Quote:
The timing of a tooth or two either way on the valve train should not effect starting... I'd set it to factory spec and leave it.
Unless the injection pump is gear driven off the cam shaft. Injector timing is critical.
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Old 10-27-2008
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Rockter will become famous soon enough
Valve timing is also critical though.
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