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Volvo 2003 engine will go straight into full revs. Throttle…

Hi, Volvo 2003 engine...

Hi, Volvo 2003 engine will go straight into full revs. Throttle does nothing ?

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Engine over revs

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Customer reply replied 3 months ago
The engine starts fine.
It starts revving and goes up to 3200 rpm plus. the throttle is at idle. The kill does not have effect. I kill the motor with some effort by suffocating the air inlet.
Answered in 9 hours by:
3/27/2018
Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 17,826
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
Verified

G​ood morning my name is ***** ***** am I speaking with? I read what you wrote. Do you have the tools to compression test the engine? When was the last time the oil was changed? Does the engine have the correct oil in it?

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Customer reply replied 3 months ago
Hi Jason, John here.
I do not have a compression tester on hand.
The oil is routinely changed.
The oil is the correct grade. The engine has been running fine. The boat is on the hard ready to go back in.I suspect there is some dirt in the hi pressure fuel pump that is keeping the stroke at full stroke even when the throttle lever is turned down or off.
Customer reply replied 3 months ago
I am sending the pump in for teardown and service.

Hi John, To be honest you want to start by changing the oil and then having the engine compression tested. When a diesel engine revs to full throttle on it's own, it does that because it's burning lots of oil. When you stop the engine, what you are doing is closing a fuel solenoid, and shutting off the fuel supply to the engine. This takes the fuel away from the engine, and shuts it off. Even if there was dirt in the injector pump, or dirt in the fuel solenoid, the engine would run, and would have a hard time shutting off, but it would not jump to full throttle by itself. Diesel engines are very simple. If you want the engine to speed up, you add fuel, if you want it to slow down, you take away fuel. What is happening is the engine is the engine is using the engine oil as a fuel, and burning that oil. That is what causes it rev up to such a high RPM. There are a couple of things you want to check.

1. Check to make sure the crankcase breather is not clogged. If it is clogged, the crankcase will not ventilate, and oil will get pushed past the piston rings, and up into the combustion chamber, where it will burn. (Some people call a crankcase a sump, the words are interchangeable.

2. Change the oil, and push fresh oil in it. IF the oil is thinned out, the same thing will happen, it will get pushed past the piston rings.

3. Pull the injectors and compression test the engine. For a minimum pressure you would be looking for 375 PSI or better. If it's low, the engine has either worn rings, cracked rings, or stuck rings from carbon buildup. From here you would decarbonize the engine, and retest the compression to see if it comes back up or not.

4. If the compression is good, then the final step would be to pull the cylinder head off, and replace the valve seals. That is what needs to be done. Does that all make sense to you. I think that should do it. But I work for tips so I do want to make sure you are happy with my service before you go. If you had a further or more specific question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

Questions do not close out, so if you have to come back later on with follow up questions to the issue you still can even after doing a rating.

Thank you
Jason

Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 17,826
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
Verified
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Customer reply replied 3 months ago
Hi Jason, thanks for that answer. I understand what you say is the engine is using the lube oil to keep running and that points to not being able to breathe or worn mechanicals or both. I hope that is not the case:). Will keep you informed. thanks for that.

You are very welcome. Thanks again and good luck!

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