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So I had a faulty carb, it dumped fuel into the motor, Holley said it was a faulty check valve....fixed!
Decided to change the oil.....it had 2 quarts of gas in it!!!!! Fresh oil in and I fired it up, ran like junk, smoked something fierce and it started leaking out of the filter! Gas! Gas again! Carbs are good, big block rebuilt last year, ran great last year!
Gas pressure was bouncing all over the place up to 7psi back down to 0psi and back up to 7 etc etc .... the fuel pump is going on 20 years old, sooooo If the fuel pump diaphragm is bad will it dump fuel into the pan?
Take it easy on me I'm young(ish) and still learning and figuring stuff out. It was my dad's car and I just want it back on the road!
Lets back up a minute.
Check valve on a Holley? The only check valve I can think of is in the accelerator pump circuit "well". And even then, if that fails, I don't see fuel dumping into the carb.
It usually just dribbles down on the Intake.
Let's think about gas getting into the oil pan for a moment. The Intake plenum would have to be flooded. And you said two quarts flooded. From there, it would have to drain into the cylinder heads.
Then, an Intake valve would have to be open. Then, the gas would sit on top of the piston for a second, slip past the rings and on down into the pan.
That is a lot of gas.
When the pump diaphragm fails, gas usually drips out of the weep hole on the pump.
Will gas go from the pump to the oil pan? IDK.
I think there is an oil drain hole for the pump pushrod in the block.
Maybe somebody has seen this happen.
You say carbs are good. Meaning plural? Two carbs?
Not sure why your fuel pressure is all over the place. Perhaps it is time is a new pump.
Sorry, they are Holley 450 tunnel ram carbs. Yeah it was spraying out of the vent tube into the carb....lots of gas. Rebuilt the carbs, float bowls set correctly, replaced needle and seat and it kept happening again. Under the squirter there was a small block and ball thing ..check valve? I don't know. It was stuck together. Replaced those (didn't actually come in the kit I ordered from Holley) now the carbs seem good.
First of all, Oh Dear.
Second of all, oh dear, that's a lot of CFM
The red umbrella type valve is a check valve. But would not, should not, could not flood the oil pan.
You have fuel spraying out the fuel bowl vent tubes.
Way too much pressure for the needle & seat to contain.
Or, you have pin hole in the bowl floats.
Or, that little "O" ring on the seat is leaking.
What size needle valve seat assembly? There are a few larger than stock options. Maybe that is the issue. The little window or port in the seat is too large for your app.
Update.
Just went back and looked. You do not have brass floats. So the pin-hole idea is out.
However, those black types of floats can get saturated. Then sink. Then the needle valve can't close. Then fuel gushes out the vent tubes.
The fuel gushing has been taken care of, carbs are good now. It was something called a check valve....power valve? check ball thingy. The ball was corroded. Just thought maybe a torn or ruptured diaphragm on the fuel pump could pump gas into the pan
2020 Corvette of the Year Finalist (performance mods)
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Your fuel pressure tells the story....holley carbs don't like fuel pressure above 7 psi...happier at 4 psi....and your fuel pressure should always be stable. Get a new pump, maybe a regulator and start from there... the fuel bowl float valves can fail if the pressure it too high and it will push past it and flood your engine , wash the cylinders flood your oil and ruin an engine if run too long that way....if the diagram fails you would be hard pressed to get fuel in your block but stranger things have happened
Fuel in your oil is a bad thing indeed. I would be extremely concerned to the point of overkill.
just doesn't sound like the things you have done should have fixed the issue.
I know it's a Bitch to remove a mechanical fuel pump in a C3. But I would if it was my car.
Something about sleeping at night.
sooooo If the fuel pump diaphragm is bad will it dump fuel into the pan?
Oh hell yeah
I worked on a 69 Camaro after it had been parked in a garage for 10 years
Everything was working fine but the oil pressure was very low.
Mechanical fuel pump dumping gas into the crank case
Thin oil low pressure. I didn't drive it till I figured out the oil thing
After that it was fine
Here's another vote for possible leaking fuel pump.
Several years ago my engine started making a knocking noise. I was pretty sure it was the main crankshaft bearings. After discussion on this forum and recommendation from a member named Leigh, I took it to a very reputable engine builder named Jeff Keown. He swore it was a bad fuel pump that allowed gas to leak into the oil which destroyed the bearings. The resulting chaos also led to several broken piston skirts. FWIW, it was an Edelbrock fuel pump.
Replace the fuel pump, I had a 1970 Cadillac De Ville with a torn pump diaphragm that pumped fuel into the the oil pan, Replaced pump , problem solved .
What I said, about sleeping at night. .....
fuel in oil, ..... Bad! ..... fuel pump diaphragm may be at fault, even maybe, ......
Sleeping at night.
Even maybe......? I don't know brand new freshly built motor, has about 17 miles on it. I ran it for about 15 seconds and it spewed out the oil filter and shot out the side of the fuel pump. Popped the intake and heads off everything looks okay up top anyway. Drained oil and cut open filter, no glitter
Gas in oil
