High oil pressure smell of gas in oil

[WrenchNhammer]

I recently had problems starting my Mercruiser 5.0 carbureted. While troubleshooting and lots of failed startup I finally found the problem. Bad shift interrupter. Boat starts and runs good, but oil pressure goes to over 65 after a few minutes.Then it sputters and won’t go over 2k rpm. I checked the oil and it does have a gas smell and is a little high. It has a new oil pressure switch. Is the engine going into limp mode because of high oil pressure? There is no alarm and I’m trying to figure out what’s going on. Any suggestions would be helpful

 

[dubs283]

no such thing as limp mode for high oil pressure, and a carbureted engine does not have a limp mode. some of the thunderbolt five modules have a knock sensor

most likely the engine is flooding out from an improperly tuned carb or carb in need of a rebuild. this would account for fuel contaminating the oil

65 psi for oil pressure at 2k rpm sounds fine

 

[Scott Danforth]

Gas would make oil thinner and oil pressure should drop

There is no alarm on oil pressure higher than 10psi

If you have a mechanical fuel pump, the diaphragm could be leaking

 

[WrenchNhammer]

What else would make it back fire and putter when RPM rise? I’ve played with distributor timing no luck so far

 

[Scott Danforth]

How are you "playing" with timing?

If you have a "crab cap" style distributor, change the cap and rotor

Other things that can cause a backfire or lean sneeze is improper timing, running lean, poor fuel quality

Fuel smell in oil means there is a lot of fuel in the oil. Your carb may have a bad needle and seat.

What vintage motor? 2 barrel,or 4 barrel?

 

[WrenchNhammer]

I had just previously replaced the distributor assembly and rebuilt the carb I did scar up one of the 3 brass cones with a screwdriver. I wonder If it’s disrupting my flow? Also I forgot to tighten my cap and towed it a distance. I checked timing and it seemed right. It’s making me think the timing is just off a bit and is advancing too far. I have another ICM I may try it as well tomorrow

 

[WrenchNhammer]

Could my fuel pump be going out?

 

[Scott Danforth]

Could my fuel pump be going out?

Dont know. mechanical or electrical. Im guessing hear because you have not posted year

 

[WrenchNhammer]

Electric fuel pump

 

[Lou C]

The other thing that can cause high oil pressure is water in the oil. If you’re not seeing it on the dipstick look inside the valve cover

 

[Scott Danforth]

Electric fuel pump

if an electric fuel pump goes out, there is no diaphragm to leak internal to the motor. there simply is no fuel supplied to the motor.

did you test pump pressure?

did you put a mechanical gauge on the engine to actually read oil pressure? or are you relying on the accuracy of the cheap electric dash gauge and sender (where if you have a connection issue, your oil pressure reads higher)?

 

[WrenchNhammer]

No I guess that’s my next steps. The more I think about it the more I’m convincing myself the timing is off. Because it only misfires when I go above 2k RPM. It’s either that or my fuel pump isn’t pumping enough

 

[WrenchNhammer]

How would you recommend testing the fuel pump?

 

[Rick Stephens]

Fuel pump is tested with a pressure/vacuum gauge placed inline. There are fittings made to tee solid fuel lines. Carbs need 4-7 PSI.

Set your timing correctly. Use proper procedure and a timing light. Don't ever just wriggle it around looking for a sweet spot. That's a great way to burn holes in pistons.

 

[Lou C]

And if you are using an advance timing light when setting base timing make sure the dial is on ZERO...this tricked me a few times....lol....
PS take a look at the center electrode porcelain on your spark plugs, the depoits on this will tell you if its running out of fuel (probably blistered white) or flooding out (black)

 

[WrenchNhammer]

When I first started the boat today it ran perfect for a good 10 minutes. I checked timing and it was a bit advanced so I went through the whole process of making sure is was set at 10deg btdc base timing. It had started to big down before I began. I noticed I never heard the fuel pump kick on with key on on position. It was pumping with engine running however. It sounds like it’s starving for fuel and it pulsates. I’m thinking I may have a connection issue or a fuel pump not deluging enough fuel. Thoughts?

 

[Scott Danforth]

and your fuel pressure is?

 

[WrenchNhammer]

Holding at around 60

 

[Scott Danforth]

Holding at around 60

Your fuel pressure is 60psi? On a carbureted motor?

Cant happen. Carbs are generally 2-5 psi, 6 max. Above 7 psi, the needle and seat wont close

60 psi is also higher than EFI motors (45 psi)

So, what is your fuel pressure?

 

[WrenchNhammer]

I read that wrong I didn’t check the pressure yet I couldn’t get a gauge yet