Re: Fuel bowl draining …
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Forum Ambassador
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You didn't mention if the filter is the optional in line type mounted next to the carb or is the type mounted directly on the old prewar fuel pumps.
Assuming it is the optional type next to carb, I suspect even though you are not smelling gas it is being percolated out of the bowl into the carb and manifold or more likely, since todays gas is so volatile residual heat could be making it disappear as a vapor rather than a liquid. If the filter is the optional ceramic or paper type with the glass bowl and the placement and plumbing is correct, there should be no way for the fuel to siphon back to the pump or out a faulty flare in the line. The inlet and outlet ports exist as just flat openings in the top casting separated to function for the filter element by the gasket and a couple of thin protrusions in the casting. They are above the filter element and fuel level. As soon as fuel drops in the glass bowl it should allow the air at the top to break any suction. There are also valves in the pump which would work effectively the same way as a check valve if fuel was trying to get thru the pump. Those must be working because the pump is able to function.
Posted on: 2021/9/13 18:55
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Howard
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Re: Fuel bowl draining …
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Just can't stay away
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So as far as the fuel filter , it’s a replacement glass type . Should it be inverted (glass up ) or not ?
It’s just rough on the starter trying to get gas pumped back up to the carb . Maybe a shot of gas may help ?
Posted on: 2021/9/13 19:07
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Re: Fuel bowl draining …
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Forum Ambassador
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Here is a typical glass bowl filter on a 47 carb. This element is paper but Packards optional filter was ceramic. All years and single carb installs mount in the same orientation -- glass bowl down -- and relative location, the only difference being the style of carbs. in the case of 55-6 dual carbs, filter is in the line just before it splits and goes to the separate carbs.
As to the long cranking, that is somewhat typical with volatile fuel and a few days sit. Many of us have electric pumps mounted near the tank and operated by an independent under dash switch primarily for that reason. Turning the pump on a few seconds so gas is pushed up into the bowl and carb before trying to start the car will save a lot of cranking time.
Posted on: 2021/9/13 19:17
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Howard
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Re: Fuel bowl draining …
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Just can't stay away
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Ok yea that looks just like my fuel filter , about 1/4 full ….. so 2 things
1) what fuel pump can I use ? 2) I have a outlet for 100% petroleum gasoline now , wonder if that would help ?
Posted on: 2021/9/13 20:01
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Re: Fuel bowl draining …
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Forum Ambassador
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Cannot answer if the fuel type will make a difference. Here in Calif we have had various additives required by the air resources board in their efforts trying to cut air pollution for so long I doubt very many remember pure petroleum fuel, myself included.
As to the pump, I would recommend a solenoid type electric placed inline just after the tank. Unlike most rotary pumps, the mechanical pump can pull fuel thru a solenoid type pump without it needing to be on. As an added benefit with that mounting location, the fuel is pushed thru the mechanical pump so the electric pump would also be useful in cases of vaporlock. Do make sure the rubber in the mechanical pump is in good condition though. With your new rebuild that should not be a problem. Airtex makes a couple of decent 6v solenoid type pumps that will work and are sized for the 5/16" fuel line. The E8902 has a pressure out of 2.5-4.5 psi which closely matches the mechanical pump output. It is a bit low to push fuel thru the line and fuel pump and then the filter but should still work with the paper filter element without issue. For pushing fuel thru a ceramic element, the E8011 at 5-8 psi might be the better choice. By the time fuel gets thru the length of the line and the fuel pump the starting pressure will have dropped a bit and after the ceramic filter it should be in a satisfactory pressure range to not flood the carb. Some parts stores carry Airtex but most will have some brand pump -- but do try for a solenoid type and pay attention to the output pressure. Amazon may still carry some Airtex models too. Electrically, if you want you can power from the coil terminal at the back of the ign switch. That way the pump will only operate with the key to the right or run position. If you prefer to use the GA terminal where an accessory is typically powered, it will work with key in either direction. Place an inline fuse of 10 amps (or whatever the install instructions recommend) in the wire before an on/off switch and then mount the switch on the dash edge so it is hidden. Some of the dashes may have an extra hole just perfect for a switch.
Posted on: 2021/9/13 20:48
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Howard
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Re: Fuel bowl draining …
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Home away from home
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Don't know if this will help or not, but my glass bowl used to drain somewhat between runs. It would be at 2/3 full when shut off, then over the course of a day or two it would drop to 1/4 or so. In fact, the bowl would never fully fill when running.
A few weeks ago I finally got around to repairing two leaks in my fuel line....one at the back of the main line at the tank, where it connects to the tank, and the second at the front of the main line where it connects to the flex line at the pump. Turns out both of the original flares had gone bad (split) and were slightly leaking fuel when the pump was not running, as well as sucking air when the pump was running. No leaks now, and interestingly enough the fuel bowl now is completely full when I run the car, and stays completely full for many days afterwards. My guess is that the leaks caused air to either enter the lines and force fuel out of the bowl. Or the leaks caused the fuel system to lose pressure and the fuel would drain back somewhere. -Kevin
Posted on: 2021/9/13 22:01
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Re: Fuel bowl draining …
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Just can't stay away
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Hi Everyone. Assuming there is nothing wrong with your fuel pump, could I suggest an electric pump in series? On my engine I also found the heat from the block and manifold simply evaporated the fuel from the pump and line. I got an electric pump from onlineautoparts, it is 6V and works with pos earth, and doesn't have to be on all the time. I use this for starting so I don't have to crank the battery to death getting fuel up from the opposite corner of the car.
Hope this helps. Gary
Posted on: 2021/9/14 4:47
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Re: Fuel bowl draining …
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Home away from home
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You got an air leak somewhere, as Kevin noted on his car. Air leaking in, suction is broken, that's what's causing the fuel to drain back. The fuel pump check valve(s) must be faulty to allow back flow. There's been a lot of issues with new replacement mechanical fuel pump valves since they moved the manufacturing. Once it's liquid full there's not any good reason for it to "disappear" and not leak liquid.
Liquid seeks it's own level, so once the motive force (pump is off) the gas is seeking it's level and draining back to the tank. There's not enough volume change in the tank (large surface) to displace any vapors to cause a smell. The flares should be SAE double inverted on the fuel line, unless you switched to AN fittings. Much misinfo about fuel bowls because they've been out or use for so long. If it was "boiling" out you'd see bubbles. Plus only about half of the ethanol will evaporate. It co-distills with some hydrocarbons and once it's a certain fraction, BP raises enough to stop the boiling, plus the car is cooling off once it's off. You're better off finding and fixing the leaks than installing a booster electric pump. I've had so many bad mechanical pumps come through I've gone to complete electric on the Cad, but you have to do a bunch of safety wiring so it shuts off and turns on when starting. Not straight forward but there's info on net and form Airtex.
Posted on: 2021/9/15 20:00
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