Has anyone ever heard of or experienced fuel slipping or sipping by mechanical fuel pumps when the engine is off and like a full tank of gas? And MAYBE even parked on a hill?

And with that having your carb flood with gas and get in the engine and fill up the crankcase?

 

Sounds more like a hole in the diaphragm.

 

I've heard all sorts of things...

I've heard that you have to be careful in bars because you might wake up in a bathtub full of cold water, missing a kidney. Do I know of anyone that it has ever happened to? No... Do I know of any documented instance of it happening to anyone who, say, reported it to the police? No.... Does that stop people from posting it on the Internet? No...

On top of that, is your carb EVER going to be BELOW your gas tank? How much of a hill could you possibly park on, that would make that happen?

Cars ALL had carbs for about 100 years. People - ALL people, including your great-grandmother most likely - drove them EVERYWHERE, parked them EVERYWHERE, used them for EVERYTHING, in ALL weather, ALL the time, and didn't have things like that happen to them. Don't worry about it.

Don't outsmart yourself over superstition and make-believe fantasy-land drivel like that. Just make sure your fuel system is in good shape with no restrictions between the tank and the pump, buy a good-quality stock-replacement pump, get a lightweight drive rod, and enjoy.

 

On top of that, is your carb EVER going to be BELOW your gas tank? How much of a hill could you possibly park on, that would make that happen?
Cars ALL had carbs for about 100 years. People - ALL people, including your great-grandmother most likely - drove them EVERYWHERE, parked them EVERYWHERE, used them for EVERYTHING, in ALL weather, ALL the time, and didn't have things like that happen to them. Don't worry about it.QUOTE]

Except in one documented instance where a fellow hot rodder (who was actually my engine tech professor) had a model A Ford with the cowl gas tank. It was a gravity feed directly to the carbs (3 x 2 barrel). On one occasion, the petcock from the tank to the carbs was left open over night and the contents of the tank emptied into the carbs and on into the crankcase.
For the record...

 

Well that's what happened to my camaro, and it's the ONLY thing I can ever come up with.

Apeiron
Somehow the fuel pump got hit and dented a little bit which probably maybe it get a hole in the diaphragm.

sofaking
Well I have no other way of explaining how all the gas got into the crankcase on my '84 when it sat. I mean it was FULL to the brim. Somehow it like siphoned it or something because it was on a slight hill.

skinnyz
So I think it IS possible for it to happen.

ANYWAYS...I don't mean the thread jack. I just read this about fuel pumps and thought of my issue. I ended up putting on a carter fuel pump and it's been good ever since.

 

How sure are you that it happened while it sat?

 

RocketyMan, please keeps posts on-topic to the thread in which you are posting, or start a new thread. Thank you.

 

Well when I picked it up and had it towed back to my garage...i drained out like 8 quarts of this oily but very sour gas smelling fluid.

I just can't come up with any other explanation.

The car runs now! (rebuilt carb, new plugs, fresh oil, new fuel pump..etc.) But...I think having all that gas in the crank did something to the rings because it burns a little oil when I turn it over from sitting weeks at a time (i.e. during these winter months I like to turn it on to get the engine moving and not sitting all winter). It'll eventually clear up when the engine gets fully warmed up.

 

five7...hey I didn't mean to jack that thread. The only reason why I rang in was because I still thought it was relevant to the topic. I didn't mean to draw attention away from the original post.

 

How do you know it wasn't there when you shut it down?

 

Hmm...maybe I'm having trouble being clear.

Well basically...this camaro was sitting under a tree for 5 years. And it has seen the worst effect of neglect. The paint was all oxidized, interior was a lil wet on the floor :X , the hydraulic clutch line had a gowge in it, and more importantly the hood release was rusted shut! -_-

So before I REALLY knew what condition the car was in, I had it towed up to my garage. And it was from there I crawled under the front and popped the hood open to find two HUGE rate nest. After cleaning out the car, I pulled the dipstick and it had this oily sludge on it and it rank! It wasn't water logged...just black and disgusting.

To try and make a long story short, I drained the crank to find it had LOADS of gassy / oily fluid in it. It filled up my drain pan several times.

The gas tank was of course completely empty at the time. And before the car sat for such a long period, it was sort of in very poor running condition. This camaro has been a huge TLC project. I eventually got it up to running very good! It goes into closed loop (the dwell adjust when idling, so I'm assuming it goes into closed loop), and sounds like it hits all 8 cylinders pretty good.

I'm only assuming the gas in the crankcase was caused from the stock fuel pump. It appeared to be damaged which is what probably caused fuel to keep sipping into the carb.

At any rate, I replaced the fuel pump with a carter a while ago and has been fine ever since.

 

I just went out to my garage to look for the box my carter fuel pump came in and I put the old, broken stock fuel pump in the box.

 

You can see the out-flow to carb on the stock AC fuel pump has this weird dent gouge on it.

 

Yes, but it happened when the engine was running, not when it was sitting.

 

No, I'm saying is that I think the gas slipped by the diaphragm in the fuel pump while it was sitting.

 

Yes, and I'm saying you're wrong. It happend while it was running.

 

I don't know if a SBC can even think about running with 8 qts. of oil / GASSY lubricant, without seriously hurting something...with serious amounts of gas in the crank, it completely thins the oil beyond anything.

When I took of the stock fuel pump, I could blow air through the input and have it come out the output. While on the carter it was good. So obviously if fuel wanted to slide past the diaphragm in the mech fuel pump, it could.

Besides ALL of that. The car works great with the new fuel pump and doesn't fill up the crank anymore.

 

IF the fuel tank was vented properly, allowing air in but not out, the pressure increase in the tank each time it warmed up could conceivably force fuel through the lines to the carb. As it cooled each day the vent could allow air in to displace any lost. The evap line could be clogged OR the pressure could have been greater than the evap line's metered orifice could otherwise dissipate.

The carb must also have failed though to allow any fuel past the needle/seat into the motor.

The pump does not have to be bad for fuel to pass through to the carb. I've been using a non-functioning stock pump (no push rod bore) as a means of fuel supply and return with a second electric pump near the tank for years. I've verified both return (with return line disconnected) and supply (motor still runs when I start it).

 

Hmmm..yeah that's an interesting note.

But at the time the carb didn't have the dwell screws epoxied or anything like that. So it very well could have been dripping fuel down into the intake.

And as far as the pressure in the tank expanding and pushing fuel through the lines..well that could happen to I suppose.

 

I have seen this exact problem happen one time to a friend of mine's '69 Corvette.

He was parked on a hill, facing downhill, as it were.
He got in the car hours later, and no start, imagine that!
I towed the car in for him, and checked a few things, checked the oil, and guess what!?

We drained the oil pan, changed the filter, then took the carb off, and rebuilt it. A Qjet.

The needle valve was leaking, and since the fuel system was primed from tank to carb, gravity managed to cause fuel to seep through, filling at least one or more cylinders (via open valve), bleeding by the rings, and filling the crankcase until it couldn't take any more!

Yes, it can happen with carbed engines, and NOT just through the FP.

 

Well that is certainly good to be reassured that these things do happen. And that with a good carb rebuild and correctly working FP will minimize the chances of getting fuel in the crank to yours and mine extent. :X

 

The factory used a filter in the inlet with a check valve to prevent fuel going into or out of the carb when the engine was not running.

 

The tiny filter on the qjet itself? I'm not sure I know what youre talking about five7.

Do you have a picture of the valve itself?