Gas in Oil!?

[Barrett-FL]

I have two issues. One causing the other with my 86 C-10 which has a 350 with 4-barrel Ellerbrock carb and intake.

It's a project and doesn't get driven yet. After sitting a few days the gas seems to drain back from the fuel line, it takes a lot of pumping the gas peddle to get fuel to the glass fuel filter and to the carb to get it started. Once the fuel filter is full it will start right up daily, but if I let it sit a couple days it's hard to start due to the lack of fuel in the line.

The time I started it to move it it began spewing oil mixed with gasoline. I can't see where it was coming from but it covered the engine and engine bay with the fan blowing it. The oil dipstick was over filled due to the gasoline and one could smell the gas on the dipstick.

I drained the oil and replaced the filter and ready to refill the oil but I'm somewhat afraid to do so and to start it without knowing what happened and how to stop or avoid it from happening again. I would hate for it to do it again and repeat the process.
Has anyone had issues with gasoline getting into the oil and what I can do to solve it?

I appreciate any sound advice.

Thanks!

 

[78C10BigTen]

Sound like the diaphram in the fuel pump may be bad and lettin gas into the crank case. Or your carb is having and issue.

 

[YakkoWarner]

I experienced this twice - once on a large GM 4 door car and once on a Jeep with a 2.5L GM engine. In both cases, the diaphram on the mechanical fuel pump had ruptured, so as the engine was turning the pump was cheerfully filling the crankcase with fuel. Not fun, definately check it before trying to run the engine again because otherwise you'll have just wasted/contaminated another 5qts of oil.

 

[Barrett-FL]

Thank you for your responses.

I suppose the best thing to do is replace the fuel pump and give it a try.

One thing I’m concerned about is where did the oil leak out from and will the oil leak out again when running.

Also, will replacing the pump stop the fuel from leaking back from the fuel filter?

Thanks again!

 

[fast 99]

Fuel pumps have check valves. Replace the pump then if problem persists move on to other areas.

Suspect ethanol fuel did some of the damage.

 

[TotalyHucked]

If it were me, I'd start by first looking around the engine bay for any other leaks - coolant hoses, transmission lines going to the radiator, freeze plugs popped out, anything. Then clean the engine bay really good with either brake clean or Gunk and a hose (being careful to not soak the distributor/alternator/anything electrical) and reinspect.

I would then replace the fuel pump cuz that's the likely culprit of the fuel in oil issue. Then take the wire off the coil and dizzy and have a helper crank the motor over for a bit (don't crank the starter more than 20-30sec at a time or you could burn it up) and see if oil comes out anywhere without the engine running. You may need to do this for 5-10min before oil starts getting to the top end/anywhere out of the pan. Just like priming a fresh motor. If it does come out anywhere, it'll probably just ooze out since the motor won't be spinning very fast.

If not, then hook the coil wire back up and again have a helper start the truck while you look for leaks underhood. I've never run across a vehicle that "spewed" oil like you describe so I wonder if it was a transmission line with a pin hole or something else.

 

[Barrett-FL]

If it were me, I'd start by first looking around the engine bay for any other leaks - coolant hoses, transmission lines going to the radiator, freeze plugs popped out, anything. Then clean the engine bay really good with either brake clean or Gunk and a hose (being careful to not soak the distributor/alternator/anything electrical) and reinspect.

I would then replace the fuel pump cuz that's the likely culprit of the fuel in oil issue. Then take the wire off the coil and dizzy and have a helper crank the motor over for a bit (don't crank the starter more than 20-30sec at a time or you could burn it up) and see if oil comes out anywhere without the engine running. You may need to do this for 5-10min before oil starts getting to the top end/anywhere out of the pan. Just like priming a fresh motor. If it does come out anywhere, it'll probably just ooze out since the motor won't be spinning very fast.

If not, then hook the coil wire back up and again have a helper start the truck while you look for leaks underhood. I've never run across a vehicle that "spewed" oil like you describe so I wonder if it was a transmission line with a pin hole or something else.

Thank you for your time and knowledge.
The oil had the strong snell of gasoline and was way up over full on the dipstick so I believe that as well and thinning of the oil was what was causing the oil to spew… I just can’t see where it spewed from as yet.
I’ve drained and replaced the oil and the filter and purchased a fuel pump and hope that corrects the issue. If not, I’ll move on to the Edelbrock carb.

 

[Chebbyman]

I have had this happen twice on mechanical fuel pumps on sbcs. These pumps have a”weep” hole that alerts the observant owner that the diaphragm has failed or is failing by squirting gasoline out the hole. As the lever side is open to the oil pan on the inside of the engine, it can also eject fuel into the oil system. I vote bad fuel pump. Do not wait until you wash the oil off your bearings to learn this the hard way. Buy anew pump.

 

[1lejohn]

It's normal for the carb and the feed lines to go empty after several days. The new gasoline evaporates very quickly. It is engineered for modern fuel injection engines and emissions. My truck does the same thing. You have to fill the fuel bowls on the carb before it will start. If it sits for a week, you can spray starting fluid or squirt some gas down the carb.

 

[hack_man]

I have the same problem having to crank and crank a long time after it's been sitting for a week. I've found if I set the choke with a firm press of the gas pedal and maybe one more pedal pump, just leave it for 10 seconds or so with foot off the gas, then Turn the key (foot off gas). If it still doesn't start, repeat.

Its definitely temperamental after sitting a while.

 

[Walstw01]

I had/have a similar problem, with my '79. Fuel drains completely from carb to fuel pump. Fuel pump was trashed (but I didn't have gas in the oil). Replaced fuel pump and still had the fuel drain-back issue. I installed a fuel shutoff between the fuel filter and pump. As long as I remember to engage the shutoff if the truck is going to sit for a few days (and remember to disengage it again) it starts right up like it should.

And I run 90-91 fuel.