Carburetor leaking into oil pan. What gives?

[vol_bronco_05]

Anybody ever have a problem with the Autolite 2100 leaking slowly leaking fuel past the power valve and draining into the oil pan? The truck sits for long periods and it is always hard to start the first time. I have rebuilt the carb several times including the power valve and it runs great but I eventually notice a leak right under the power valve. I take the PV cover off and it is full of fuel.

I'm debating on spending $200 on an O'reilly rebuilt unit but I would hate to spend that kind of money and not need it if there is a common fix for this (besides EFI)

Any help would be greatly appreciated.

 

[Airmapper]

Is there a crack in the housing or something? My Dad's was leaking in the same place but a new seal took care of it.

I'm not sure what your talking about on the oil pan though. Do you mean the intake manifold?

 

[oleguy74]

change power valve.be sure to get same no.

 

[jckkys]

The covers on most the 2100,2150, and 4100 carbs have been over tightened and the four ears are bent so the gasket surface can't seal. When you take the power valve cover off set it against a flat surface. If you see light between the screw holes,the cover has been over tightened. I use a vice to bend the ears back to get a flat gasket surface. If you file the surface flat you loose the ridge cast into it that helps seal the gasket. The accelerator cover has the same problem on Ford and Holley carbs. Holley has inch/pound torque specs for all screws they would be good for Ford carbs too.

 

[pcf_mark]

How does it get to the oil pan? If it leaks in the intake won't it run into any open cylinder and either evaporate or puddle in the cylinders until the carb is empty? The most it would be is an ounce or two of fuel. If you have fuel in the oil pan then it may be leaking at the fuel pump diaphram that is lower thean the fuel tank and it can keep on leaking key off using gravity from the tank and dumping into the front cover and then to the pan.

 

[vol_bronco_05]

change power valve.be sure to get same no.

Where can I buy just the power valve? Most parts stores only stock the whole kit. And how can I tell if it is the right valve? I've replace it several times with whatever comes in the kits.

 

[oleguy74]

there a couple of number sys.example,a #75 is a 7.5.that would be a good place to start.

 

[vol_bronco_05]

I'm not sure what your talking about on the oil pan though. Do you mean the intake manifold?

How does it get to the oil pan? If it leaks in the intake won't it run into any open cylinder and either evaporate or puddle in the cylinders until the carb is empty? The most it would be is an ounce or two of fuel. If you have fuel in the oil pan then it may be leaking at the fuel pump diaphram that is lower thean the fuel tank and it can keep on leaking key off using gravity from the tank and dumping into the front cover and then to the pan.

Somehow the fuel is making it's way into the pan through the intake. Maybe it is getting into the cylinders and slipping by the rings? I changed the oil today and it had a very strong gas smell. I've noticed a few days after I drive it I'll see a puddle of oil on the garage floor. I'll wipe the oil up and, as long as I don't drive it there will not be another puddle until I drive it again.

 

[pcf_mark]

If you don't mind the taste you can suck on the back side and the valve should move. It should stay in the moved position until you release the vacuum.

 

[bmc69]

Somehow the fuel is making it's way into the pan through the intake. Maybe it is getting into the cylinders and slipping by the rings? I changed the oil today and it had a very strong gas smell. I've noticed a few days after I drive it I'll see a puddle of oil on the garage floor. I'll wipe the oil up and, as long as I don't drive it there will not be another puddle until I drive it again.

Every time I've had a problem with gas loading up the oil, it was always the fuel pump that was the culprit. To leak that much gas from carb all the way through pistons and past the rings in to the pan is not very likely...not completely impossible but not very likely.

 

[jckkys]

I kind of ignored the oil pan issue because it didn't make sense. The power valve hangs off the bottom of the float bowl. A leak would sit on top of the intake. It would never get to the crank case. New power valves for Holleys work on Ford carbs and are usually better quality besides being available at O'Rielly etc. Fuel going through the power valve can only go to the booster venturi with the fuel that passes through the jets. The power valve cover can leak and that was what I addressed. Fuel in the oil likely comes from the mechanical fuel pump. But that's rare because the pumps have a hole to let fuel out before it can get to the crank case. That hole would spray the front of the oil filter on small block Fords.

 

[vol_bronco_05]

Every time I've had a problem with gas loading up the oil, it was always the fuel pump that was the culprit. To leak that much gas from carb all the way through pistons and past the rings in to the pan is not very likely...not completely impossible but not very likely.

I replaced the fuel pump within the last year for cosmetic reasons but I'm not sure if this problem existed with the old pump. Is it a chronic problem with these pump to leak internally?

 

[vol_bronco_05]

I kind of ignored the oil pan issue because it didn't make sense. The power valve hangs off the bottom of the float bowl. A leak would sit on top of the intake. It would never get to the crank case. New power valves for Holleys work on Ford carbs and are usually better quality besides being available at O'Rielly etc. Fuel going through the power valve can only go to the booster venturi with the fuel that passes through the jets. The power valve cover can leak and that was what I addressed. Fuel in the oil likely comes from the mechanical fuel pump. But that's rare because the pumps have a hole to let fuel out before it can get to the crank case. That hole would spray the front of the oil filter on small block Fords.

My thought was that the fuel was leaking past PV seal to the vacuum side of the PV and filling the cover. The hole that the supplies the vacuum to the valve of course leads to the intake. Whether that is what is getting into the crankcase, I'm not sure. From what you all are telling me, it looks like I may have two problems.

I'm currently running the following test: I disconnected and plugged the filter at the carb. Then I removed the cover from the carb while it was still installed on the intake. Of course, it was mostly empty after about a week after last started. I then filled the bowl until the float came up. I have already drained the oil pan to a slow drip and left the drain plug out and then put a clean container to catch what comes out overnight.

My thinking is that this will remove the fuel pump from the equation. If I get significant amounts of gas in the drain container then that should prove the carb is the source of the leak, if not then I'll take a hard look at the fuel pump.

If there is no gas in the catch container, and it looks like it might be the pump, does anyone know of a practical way to test the pump for leaks? I would rather not take it off if possible since I would have to take the PS pump off. Maybe leaving the line loose at the carb and filling the line while still connected to the pump and seeing if anything drains out of the pan into the catch container?

 

[pcf_mark]

You say power valve (PV) but you are referencing a hose to the valve cover I think. The hose to the valve cover is for the PCV valve. The power valve is down inside the float bowl of the carb. If it was completely removed the most fuel that would go into the engine would be whatever is in the bowl then run dry. This could be a shot glass worth and would be burned off when the engine started. The PCV valve uses engine vacuum to draw crankcase pressure through the valve cover and back into the intake to burn them. It would take a tank of gas to fill the intake and any open cylinders to get fuel up high enough to reach the fitting for the PCV. Also the check valve would keep anything from flowing down the hose.

The mechanical pumps do not like ethanol fuel it rots the diaphragm then they leak. I have put two airtex pumps on in four years. I have never had one leak externally when they failed both leaked into the crankcase and stunk up my garage something awful or left me on the side of the road!

 

[vol_bronco_05]

You say power valve (PV) but you are referencing a hose to the valve cover I think. The hose to the valve cover is for the PCV valve. The power valve is down inside the float bowl of the carb. If it was completely removed the most fuel that would go into the engine would be whatever is in the bowl then run dry. This could be a shot glass worth and would be burned off when the engine started. The PCV valve uses engine vacuum to draw crankcase pressure through the valve cover and back into the intake to burn them. It would take a tank of gas to fill the intake and any open cylinders to get fuel up high enough to reach the fitting for the PCV. Also the check valve would keep anything from flowing down the hose.

The mechanical pumps do not like ethanol fuel it rots the diaphragm then they leak. I have put two airtex pumps on in four years. I have never had one leak externally when they failed both leaked into the crankcase and stunk up my garage something awful or left me on the side of the road!

Sorry for the confusion, when I said PV I meant power valve. I know I may also have thrown a few off when I said I leaked from the power valve into the oil pan. I SHOULD have said past the power valve, into the intake, into the cylinders, past the rings, and into the crankcase.

The puddle of oil I mentioned was, in my mind, from the oil level rising due to the fuel in the pan to the point where it got up to the dipstick tube. I siliconed the dipstick tube into the pan and my thought was the gas in the oil broke the silicon down and started leaking. I might be way off on that but I do know my carb bowl goes empty in a few days and my oil stinks of gas and is pitch black. That can't be good for an engine.

You might be onto something with the ethanol statement. I didn't know old cars did not like even small amounts of ethanol until a friend told me about a year ago. I have since rebuilt the carb but this pump may have been replaced before I stopped using 10% ethanol fuel so it may be shot. Looks like I might need to replace the fuel pump.

Thanks for the input folks! What a great community!

 

[jckkys]

After thinking about it no fuel should get below the power valve. If that happens either the diaphragm has a hole or the gasket between the power valve and the float bowl is leaking. A perforation of the power valve diaphragm would cause an over rich idle. That's a high vacuum condition and the extra fuel makes for a terrible idle, if it can idle at all. If the round power valve gasket is leaking, screw the power valve in a little tighter. Sometimes the threads are full of crud making it feel like the valve is tight enough to seal when it's not.
Your correct in that fuel that gets below the power valve would enter the intake at the base of the throttle bores. I just checked on one of my disassembled 2100s. Removing the power valve cover should tell the story ie. it should be dry with no trace of gas. If you find gas, get a Holley power valve rated at about 8.5" Hg. They come with a gasket.

 

[broncnaz]

Sorry for the confusion, when I said PV I meant power valve. I know I may also have thrown a few off when I said I leaked from the power valve into the oil pan. I SHOULD have said past the power valve, into the intake, into the cylinders, past the rings, and into the crankcase.

The puddle of oil I mentioned was, in my mind, from the oil level rising due to the fuel in the pan to the point where it got up to the dipstick tube. I siliconed the dipstick tube into the pan and my thought was the gas in the oil broke the silicon down and started leaking. I might be way off on that but I do know my carb bowl goes empty in a few days and my oil stinks of gas and is pitch black. That can't be good for an engine.

You might be onto something with the ethanol statement. I didn't know old cars did not like even small amounts of ethanol until a friend told me about a year ago. I have since rebuilt the carb but this pump may have been replaced before I stopped using 10% ethanol fuel so it may be shot. Looks like I might need to replace the fuel pump.

Thanks for the input folks! What a great community!

Dont worry your first explanantion was clear enough. A few people will always not read the whole post or just miss a critical part of it and just throw out a answer. They mean well they just missed a part.
Honestly I would just change the fuel pump. there fairly cheap anyhow. I highly doubt its the power valve as they rarely go bad. The last fuel pump i bought lasted about 6months before it started leaking. I dont think its so much the ethanol as it is the way they make rubber nowadays. just look at tires they dont last as long as they used to. They get weather cracks pretty fast.
Pitch black oil is kinda normal in older carbed engines all that means is its time to change it. You pretty much have to stay on the old 3000 mile oil change with older carbed engines. Of course if gas is diluting it then that will cause the oil to thin out as well and you'll get leaks. The bronco push in type dipsticks are well known for leaking silicon wont stop a dipstick leak.

 

[vol_bronco_05]

After thinking about it no fuel should get below the power valve. If that happens either the diaphragm has a hole or the gasket between the power valve and the float bowl is leaking. A perforation of the power valve diaphragm would cause an over rich idle. That's a high vacuum condition and the extra fuel makes for a terrible idle, if it can idle at all. If the round power valve gasket is leaking, screw the power valve in a little tighter. Sometimes the threads are full of crud making it feel like the valve is tight enough to seal when it's not.
Your correct in that fuel that gets below the power valve would enter the intake at the base of the throttle bores. I just checked on one of my disassembled 2100s. Removing the power valve cover should tell the story ie. it should be dry with no trace of gas. If you find gas, get a Holley power valve rated at about 8.5" Hg. They come with a gasket.

Thanks for the feedback. I just took the cover off the power valve and it was dry. I had a terrible time with the circular PV gaskets the last time I changed it. Apprarently they are making those gaskets with the wrong material. I tightened it down and it the gasket was so thin you could still spin it. I was afraid to tighten it anymore, then I noticed the old gasket was about twice as thick as the new one. So I doubled up the old and new gaskets and it still leaked. I finally added some gas resistant gasket sealer and it seems to have done the trick.

 

[vol_bronco_05]

Dont worry your first explanantion was clear enough. A few people will always not read the whole post or just miss a critical part of it and just throw out a answer. They mean well they just missed a part.
Honestly I would just change the fuel pump. there fairly cheap anyhow. I highly doubt its the power valve as they rarely go bad. The last fuel pump i bought lasted about 6months before it started leaking. I dont think its so much the ethanol as it is the way they make rubber nowadays. just look at tires they dont last as long as they used to. They get weather cracks pretty fast.
Pitch black oil is kinda normal in older carbed engines all that means is its time to change it. You pretty much have to stay on the old 3000 mile oil change with older carbed engines. Of course if gas is diluting it then that will cause the oil to thin out as well and you'll get leaks. The bronco push in type dipsticks are well known for leaking silicon wont stop a dipstick leak.

I'll change the pump for the oil issue but, do you think that is what's causing my bowl to drain? I verified that the bowl will not drain back to the fuel pump since the needle and seat is sealing the return path. I checked my accelerator pump and it is not cracked but there seems to be seepage in that area. I'm debating on using the same sealant on the accelerator pump.

 

[jckkys]

Any carb Ford,Holley,or Carter will have empty float bowls after a few days. The fuel simply evaporates. I still recommend buying a new Holley power valve. They come with the thick gasket and have known opening point where the Autolite -Motorcraft power valves aren't marked. The threads in the bottom of the float bowl extend all the way through the hole but the threads beyond where the power valve engaged them get corroded so screwing the valve in further seems like it's bottoming out. It really isn't. The thick round gasket is cardboard. With a warmed up engine any fuel falling into the intake would be quickly vaporized and go out the top of the carb as a gaseous vapor.