Md7a volvo rising oil

[Pavel24]

Hello, i have md7a volvo engine and my oil level is rising slowly. I know its not water , because its not imulsifing . The only other logical explanation is that diesel gets in the oil .

From what i can see there only two places that could happen : fuel pump and injectors.

Did any one had simular problem with md7a or other basic diesel engine ?
What is the best way to find the problem ?

[DougR]

It could be the injectors, the seal on the high pressure injection pump behind the drive gear, or the diaphragm in the lift pump.

A bad injector will probably give some smoke and poor running, and maybe put a fuel sheen on the water. Pull the injectors and look for a wet tip and have them tested for opening pressure and spray pattern.

Visually check the lift pump for a cracked or split diaphragm. You could bypass the lift pump with an electric pump.

The high pressure pump will probably have to go to a fuel injection shop for seal replacement.

DougR

[Compass790]

Don't know your MD7a but it's a common problem for mechanical fuel pumps that are bolted to the block to leak through the diaphragm into the sump. Try smelling the oil.
Take the pump off & check the diaphragm. Hold it up to the light.

[montenido]

I had the same problem on my Perkins motor on my CSY44. The rear main seal was leaking like crazy, so I replaced it at a cost of 3 days and lots of my own labor. The problem persisted, so I had the oil analyzed and it came back at 30% diesel in the oil! I'm lucky the motor didn't run away on me. It turned out to be the diaphragm in the mechanical fuel pump, a cheap and easy fix.

I would start with the easy stuff first, that being the mechanical fuel pump. If it is not the problem, you end up with a spare pump. Then move on to the injectors and/or injector pump. Good luck and let us know what you find.

Cheers, Bill

[DeepFrz]

Originally Posted by DougR

It could be the injectors, the seal on the high pressure injection pump behind the drive gear, or the diaphragm in the lift pump.

A bad injector will probably give some smoke and poor running, and maybe put a fuel sheen on the water. Pull the injectors and look for a wet tip and have them tested for opening pressure and spray pattern.

Visually check the lift pump for a cracked or split diaphragm. You could bypass the lift pump with an electric pump.

The high pressure pump will probably have to go to a fuel injection shop for seal replacement.

DougR

I second this except that it is possible to change the seal on the HP pump. If you need to search the site for other threads on this problem. Use the "google custom search".

[Lepke]

The seal is easy to change on most pumps. A good hydraulic supply or injector pump rebuilder should have the seal, and much cheaper than from Volvo. Also can be found at bigger bearing supply companies and probably online.
If the seal on the pump is bad, check the shaft where it rubs. Sometimes the shaft will wear or get pits. There is a sleeve that can slide over the shaft and make a new surface without taking the pump apart. Sleeves are also at better bearing suppliers.

[sailah]

I personally haven't used the paper test but a quick way to check is to drop some of the oil from a dipstick onto plain paper. A ring will appear if there's diesel. Google for more info.

[Symphony]

thanks, Sailah. makes sense as a test for disparate liquids.
I hope I never need to verify if it works.

[Scubaseas]

What Lepke and DougR said. Been there, done that on a MD2. It's often the lift pump.

[01kiwijohn]

Easy things first; put a pressure gauge on the output of the fuel priming pump, crank the engine until the gauge reaches its max, about 3 or 4 psi usually. leave for a while and it should not leak down. if it does, problem is the pump diaphragm.
Alternatively, use a hand held vacuum pump and pull up a vacuum on the inlet side. Once again, no leakage is tolerable.

[Mike Banks]

Most likely source is fuel pump--and those mechanocal pumps that drive off the camshaft are often the cause when the diaphragm leaks it goes down into the sump.


I have an electric pump mounted on a bulkhead, with hoses attached, ready for any fuel emergency or use as a transfer pump. Yes it does click when it pumps, but if you are at sea in a storm when your main fuel pump diaphragm becomes perforated, you can disconnect the feed hose to that pump and feed fuel via the electric pump.

Electric pumps are not very expensive and will get you to a place where you can buy a diaphragm kit for your regular fuel pump, or allow you to motor away from a dangerous lee shore...

[Pavel24]

The motor works normaly so i guess its the fuel pump , i will take it a part and go to local shops (westmarine and marinas near by) to try and find replacement parts or just get electrical pump. Thanks everyone.

[Compass790]

Originally Posted by Pavel24

The motor works normaly so i guess its the fuel pump , i will take it a part and go to local shops (westmarine and marinas near by) to try and find replacement parts or just get electrical pump. Thanks everyone.

I'd try a fuel injection service place as they normally have lots of fuel pump diaphragms. Should be waaay cheaper than buying from volvo. Did you examine the diaphragm?

[belizesailor]

Originally Posted by Pavel24

The motor works normaly so i guess its the fuel pump , i will take it a part and go to local shops (westmarine and marinas near by) to try and find replacement parts or just get electrical pump. Thanks everyone.

While you are sorting this out be careful about running the engine, if the oil+diesel level gets high enough it can result in a run away diesel...very scary and usually catastrophic for the engine.

I agree w the other posts: most likely sources are lift pump or injector pump.

[markcoulter]

Another reason not to run it much until repaired - the lubricity of the diluted oil will be much less, resulting in drastically increased engine wear.