oil in sight tube

[menos22]

Just noticed my clear sight tube from the mechanical fuel pump to the carburetor has a small amount of oil in it. Swabbed it out with a pipe cleaner and found it to be like a light 3 in 1 type oil. No smell of gas in tube present. Could my fuel pump diaphragm be ruptured. Thought gas was supposed to be in sight tube if ruptured..

 

[km1125]

Depends on which diaphragm ruptured. There should be two, one on each side of the sight tubing. One separates the gas and one separates the oil. The gas side could fail and you'd still operate but the 'excess' gas would go into the carb, so you should run very rich and notice right away. But that still prevents gas from getting into the crankcase (which would be very bad) because there's that second diaphragm. Sounds like your second diaphragm is compromised and allowing some oil vapor (which condenses) to get into the tubing.

 

[menos22]

So I guess in need to replace the fuel pump?

 

[km1125]

Probably should plan on it. If you want to double-check, you could put a small amount of pressure on the line going into the pump (like, 5 PSI or less) and see if it holds. If it leaks down then I'd definitely replace the pump.

 

[menos22]

Think I will just replace the pump, looks like just the fuel lines and a couple of bolts, any tricks I should know about? Can this cause oil to get mixed in with the gas going to the carburetor and make the engine run rough?

 

[km1125]

I doubt it. There might a little bit of oil getting to the carb, but probably not enough to cause rough running. Are you seeing blue smoke in the exhaust? Are you using up oil in the crankcase? If "no" to both, then any oil mixing in is not causing an issue. Any oil getting in would be similar to the PCV vapors.

 

[Nater Potater]

Think I will just replace the pump, looks like just the fuel lines and a couple of bolts, any tricks I should know about?

The small-block Chebbies us a push rod off of the cam that'll slide out when you pull the pump. You can slather it with grease and push it back up into the block to temporarily hold it in place once you're ready to install the new pump.

 

[Thornton69]

Not sure if this works with the 454's but came across this once and never knew about it. Might be worth a look?

 

[menos22]

Thanks for the good info..

 

[Nater Potater]

Oh, stupid me! I saw the "1994 Sea Ray 350" and immediately went into small-block mode. However, 'turns out I was right anyway, as Chevy did the same on both SBC and BBC engines, so @Thornton69's pictures are good to go.