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Old 30-05-2021, 11:35   #1
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2004 MD2020D RPM control problem

On starting RPM go to 850 which is fine however after approx 4 minutes the engine goes to 1300 Approximately. Can not be controlled by throttle either when itís connected or disconnected. On second or third start it revs to 1300 in less time each time till on the fifth start it goes to 1300 after 30 seconds.
The following has been done by penta certified mechanic , injection pump removed and sent out serviced and returned, governor removed replaced three springs seems normal.
Mechanic has no other answers.
The throttle works fine beyond 1300 but shifting at the higher rpm is bad for the transmission as well as approaching the slip etc.
Has anyone had this problem?
Could the change in engine temperature affect Rpms?
Any ideas?
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Old 30-05-2021, 12:08   #2
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Re: 2004 MD2020D RPM control problem

Welcome aboard Donpet! I can't help you with your MD2020 but I added it to the Volvo social group.
https://www.cruisersforum.com/forums...o+engines.html
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Old 30-05-2021, 12:23   #3
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Re: 2004 MD2020D RPM control problem

Thanks
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Old 30-05-2021, 16:05   #4
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Re: 2004 MD2020D RPM control problem

Did you get advice? Yes, warming up the engine results in more complete combustion ergo higher idle for the same throttle setting, but that doesn't answer your question. I have no flaming idea.....
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Old 30-05-2021, 17:44   #5
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Re: 2004 MD2020D RPM control problem

Disclaimer: I dont know your engine,
My guess would be the problem has to be in the injection pump, governor or their linkages. Try using the stop button briefly before it kills the engine to see if that returns idle to normal. It sounds like the fuel rack or governor is sticking but I cant understand why the throttle does not affect it. Does it have an idle adjustment? I assume I'm asking the obvious there & the mechanic checked it but...
Hopefully you get feedback from MD2020 owners

Following with interest.

Please post back if you find out.
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Old 02-06-2021, 02:35   #6
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Re: 2004 MD2020D RPM control problem

It sounds like you covered all the bases, even down to having the governor springs replaced so itís hard to suggest any other things to try.... but maybe this will help!
On the skinny metal linkage that connects the fuel rack to the governor there is a small square of metal which is the method of pushing the control link into the stop position by using the manual stop lever. If this little tab is bent by over enthusiastic use of the manual stop lever, the unresponsive rapid and unpredictable idle may/ will occur. Hereís a pic of the stop lever and the tab that I posted previously on the forum and it might be worth taking a look through the oil fill hole on the front cover near the stop lever, the tab should be about 90į to the linkage but is sometimes a bit over the 90.
What were the circumstances leading up to the erratic idle if any?Click image for larger version

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Old 02-06-2021, 03:54   #7
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Re: 2004 MD2020D RPM control problem

Have you ruled out engine oil finding its way into any of the combustion chambers ?
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Old 02-06-2021, 05:14   #8
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Re: 2004 MD2020D RPM control problem

I will check the bent tab problem but think we would have noticed that when it was out of the engine. The engine spun up to max rpms after not being started for three months while we were traveling. I shut it down with the fuel stop and it starts and runs fine except for the movement up to 1300 rpms. There seems to be a relationship between the temp of the engine and the rpms. At cold it starts up and idles at 850 for 4 minutes then creeps u to 1300. On subsequent starts as the motor is run it Creeps up faster till it goes up right away which coinsdes with the motor getting warm. Could a stuck shut thermostat cause the engine to run hotter than normal and lead to running at higher rms? What and where is the thermostat located?
Thanks for the replies.
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Old 03-06-2021, 01:49   #9
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Re: 2004 MD2020D RPM control problem

On your MD 2020 itís in the cylinder head under the heat exchanger. You need to take off the heat exchanger to get it out. Pay close attention to the position of the spring and to the orientation of the thermostat, itís possible to get the thermostat in wrong way around.
I canít think of any logical relationship between engine temp and flaky Governor behavior and your mechanic has already eliminated all the pump/ Governor possibilities other than replacing the flyweight assembly and checking the cam endfloat...... Iím all out of ideas.
Pete.
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