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Old 31-08-2019, 09:10   #1
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Join Date: Aug 2019
Location: Dartmouth, NS
Boat: CS 27
Posts: 12
High pressure fuel prob at injector pump -Volvo Penta MD5A

Hello Everyone,

I'm new to the forum and thought I would try out this riddle with my diesel engine fuel issues on the forum in case anyone encountered this problem b4 on a penta. My mechanic wrote the following to post and recommended I mention to readers to please read through before answering...

"A Volvo Penta MD5A has developed a progressive fuel delivery problem beginning at the injection pump outlet. The engine had been increasingly hard to start, resulting in twice needing replacement starter motors. The mechanical low pressure lift pump functions normally and is augmented by an electric pump. Loosening the banjo bolt at the injection pump inlet produces a large flow of clean fuel with no froth or bubbles. Cranking the engine with the throttle at wide open, and verifying that the fuel rack has moved to that position produces no fuel output at all through the open high pressure pipe connection. The injection pump has been tested by a reputable diesel fuel injection service company and found to be in proper working order. The operation of the cam against the pump plunger cannot be observed due to the nature of it’s mounting. Through the above listed process of elimination, the mechanical action of the cam/plunger would appear to be the only possible defect."

If you have specific knowledge I would really appreciate an answer / advice!

Many thanks!
Troy
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Old 31-08-2019, 11:42   #2
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Re: High pressure fuel prob at injector pump -Volvo Penta MD5A

I suffered a similar problem with my MD6A, which (eventually, after much grief!) turned out to be the injector pump "stop" lever not FULLY returning after the engine was stopped and the stop handle pushed back in...... took forever to find, going through the whole system, and I ended up adding an extra spring to make sure the lever went all the way back, as well as cleaning it all up, lubricating, etcetc. You never know, maybe you have the same problem. Good luck!
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Old 01-09-2019, 19:37   #3
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Re: High pressure fuel prob at injector pump -Volvo Penta MD5A

-Remove the sea water pump, decompress the engine and crank it over. Look in the sea water pump drive hole to see that the camshaft is actually rotating, and hasn't sheared its key, or anything goofy like that. Some early MD5 engines suffered from the occasional broken crankshaft.
- If the camshaft is rotating, remove the high pressure fuel pipe from the injection pump, remove the delivery valve holder, the delivery valve, spring, washer, etc. and screw the delivery valve holder back in place. Place a thin stiff piece of wire in the fuel passage opening in the delivery valve holder and allow it to rest on the top of the high pressure fuel plunger. Turn the engine over slowly by hand and check that the plunger is actually moving up and down. Sometimes if the pump has sat idle for some time since last running, the plunger will get gummed up to the point that it's return spring cannot push it back down onto the cam. It gets pushed up by the cam and then just sits up there and won't move.
If so, a little judicious soaking with acetone on a Q tip can free it up.

DougR
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