Oil in fuel pump. Is this normal? 1984 Mercruiser 5.0L

K

kbmsound

Seaman
Joined
Feb 28, 2016
Messages
61
So, a while ago i posted about my carb not receiving any fuel from the pump. I trouble shoot the anti siphon valve, and hoses, checked the fuel separator, which was full of clean fuel, and made sure there was fuel in tank. I did the bottle test while cranking and no fuel came out of the pump to the bottle. I figured the pump must be bad. I took the pump out today and upon turning it over, some black colored oil started to come out. Maybe I am too rookie to know this but is this normal?
P.S The pump is not an electric pump, just mechanical. Thanks,
Les.
 
H

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Howdy,

If the fuel pump is bolted to the block, it is exposed to oil vapor and combustion blowby products. If your diaphragm is cracked or leaking, you can get fuel in the oil and probably oil into the pump through the hole/crack in the diaphragm.

Also, it if's been sitting for years, gasoline can 'varnish" making a dark, sludgy looking "oil" that if completely dry, causes check valves (in the pump) to stick either open or closed.

While some mechanical fuel pumps are rebuildable many are not (you cannot buy the kits anymore)

If it's not pumping, and it's an old one, it's probably time for a replacement.

Your engine is an 898?

The serial number of your engine will verify. You can probably get that fuel pump right here on iBoats.

Click the following to find your model.

http://www.iboats.com/Mercruiser-Fu...4741424--session_id.918866752--view_id.269820

There's a lot of online sources and even O'reilly's can get them....... iBoats seems to be competitive with all of them.


Regards,

RIck
 
M

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Sounds like the diaphragms have ruptured, they move in and out and create the suction/pressure. They are also the only thing between the backside of the pump and the crankcase. Oil to run out normal? well maybe, but in all cases will mean the pump is bad and has been for a while. Also means possible fuel dump into the crankcase. Smell the dipstick, bet it is time for an oil change maybe 2 in a row as oil will be diluted and may need 2 flushes..

On a Marine mechanical fuel pump there are 2 diaphragms with an outlet for a sight tube passageway in between. The sight tube runs from a fitting on the pump to the flame arrestor or carb neck. The idea is that no fuel should ever be in there, and if fuel is seen there the pump is on the way to end of life.
 
M

Mohawkmtrs

Chief Petty Officer
Joined
Jan 13, 2010
Messages
563
The arm on the fuel pump rides on the camshaft and oil in that "cavity" is normal. Smell the oil dipstick for fuel. If so = replace fuel pump.

No fuel out of the pump = replace fuel pump.
 
K

kbmsound

Seaman
Joined
Feb 28, 2016
Messages
61
So i replaced the fuel pump, which by the way had me cursing more than I expected ( pain in the ass). Boat started right up. Downside? Alternator went out. Anyone wanna buy a boat? lol...:)
 
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