Crankcase oil has slight fuel smell

[jbutler67]

Checking the oil level. Rag I wiped dipstick on had a slight fuel smell from oil on dipstick. (Rag was clean and no fuel smell. I cleaned dip stick again with new rag that had no fuel smell before wiping off dipstick. )

Checked clear hose routed from the fuel pump to the carburetor. No fuel in it. I pulled off the clear hose at mechanical fuel pump and confirmed nipple wasn't blocked.

No fuel in bilge

Engine running fine. No stalling or sputtering.

Engine crankcase oil level is constant. It's not "making oil".

Fuel pump is virtually brand new. Installed July 2016.

Before I pull off fuel pump, looking at what else it might be that is giving oil a slight fuel smell. What else, besides a bad fuel pump?

Boat specs
1988 OMC 5.0 V8
502APRGDP

Thanks in advance. I have learned so much from folks in this forum!

 

[jbutler67]

A little more info...

Did a compression test on all 8 cylinders with cold engine. Compression test done in April this year. All 8 cylinders came back around 150 (from 145 to 155).

 

[HT32BSX115]

A little more info...

Did a compression test on all 8 cylinders with cold engine. Compression test done in April this year. All 8 cylinders came back around 150 (from 145 to 155).

Howdy,

Sounds like you're on the right track, if your fuel pump is not leaking, the only other path would be from an over flowing carburetor float chamber. But If that was happening, you'd have very rich mixture when running with black exhaust smoke and probably severely fouled plugs. Very rich running usually doesn't result in liquid fuel making it into the crankcase unless you have one or more cylinders not firing at all!

I would suggest changing your oil, running it for a few hours at a known fuel consumption power setting and see if you are using significantly more fuel than before. (And do another "smell" test)

If you do still have fuel in the oil, I might still suspect the fuel pump. (They don't make them like they used to!!)

Cheers,

Rick

 

[Maclin]

Yup, what HT32BSX115 said... Do that.

 

[jbutler67]

Thanks for the feedback.

I don't have black exhaust smoke. I will pull the plugs and check if they are fouled.

I may just replace the fuel pump -- "throw parts at it", as they say.

Thanks again!

 

[jbutler67]

No Title

Pulled the spark plugs tonight. They are not fouled at all. Posted a pic showing the average look of each plug and a pic of the worst looking spark plug. The plugs were changed in the spring.

The undersides of the oil fill caps on the valve covers smell very strongly of fuel.

I guess the fuel pump is failing and leaking into the crankcase oil. Darn pump was just installed last July. I guess the aftermarkets aren't made like the original OEM parts.

 

[HT32BSX115]

Thanks for the feedback.

I don't have black exhaust smoke. I will pull the plugs and check if they are fouled.

I may just replace the fuel pump -- "throw parts at it", as they say.

Thanks again!

Yeah, I am thinking you don't have an overflowing carb if it's not spewing black smoke. It would literally be worse than running with the choke on!

One thing you could do is remove the fuel pump, connect test hoses and operate it manually(by hand)........ get it primed with fuel and and block the output line to develop a little pressure........ If it's got a leaking diaphragm you would probably see evidence of it at the operating lever pretty quick.

 

[jbutler67]

That's a great idea... I'll give that a try.

remove the fuel pump, connect test hoses [to the removed fuel pump] and operate it manually(by hand)........ get it primed with fuel and and block the output line to develop a little pressure

Thanks again for your help.

 

[Maclin]

*deleted*

 

[jbutler67]

Replaced fuel pump today. Can smell gasoline near lever of old pump. Also smell gas on oil inside pump opening in block - before I changed oil. New oil and filter installed too.

All seems good now. No more fuel smell.

 

[HT32BSX115]

Replaced fuel pump today. Can smell gasoline near lever of old pump. Also smell gas on oil inside pump opening in block - before I changed oil. New oil and filter installed too.

All seems good now. No more fuel smell.

:thumb: :thumb: Another Happy Camper!!

 

[Maclin]

Good job guys :encouragement: