Moaning sound after shutting engine off - Problem solved!

Finally got back to it. Matt said that they have have used these caps with no problems. Ran it again today for a bit....it moans some when it's running but engine noise overpowers the moan. Got under the car after shutoff and it appears to be coming from the fuel tank .?! Fuel pressure does bleed down over time....like hours or overnight.
 
This sounds to me like a problem with the tank venting system. Are all the bits and pieces of the evaporative emissions system still present? As you draw fuel out of the tank, air must be allowed to come in and replace it. There is an elaborate system of hoses, valves and separators for this purpose. Every so often something gets clogged, or someone gets a bit over eager in de-smogging a car and plugs the system.

Have a look at the FSM in the Wiki (page 10-108) and see if your evap system matches the book. Are all the hoses connected where they should be? any of the hoses clogged? Items 8, 9 and 10 operating as they should?
 
I agree with Bjorn. Just as an experiment try removing the hose from the tank vent pipe and see if the noise changes.
 
This sounds to me like a problem with the tank venting system. Are all the bits and pieces of the evaporative emissions system still present? As you draw fuel out of the tank, air must be allowed to come in and replace it. There is an elaborate system of hoses, valves and separators for this purpose. Every so often something gets clogged, or someone gets a bit over eager in de-smogging a car and plugs the system.

Have a look at the FSM in the Wiki (page 10-108) and see if your evap system matches the book. Are all the hoses connected where they should be? any of the hoses clogged? Items 8, 9 and 10 operating as they should?
Thanks for the thought, guys. I did install all of the vent system stuff as Colorado is anal about emissions and they seem to be getting worse. I tried to pay close attention to system hookup, but may have a bad valve from the car that the engine came from. All of the hoses were replaced with new and the fuel tank is new as well. I will revisit the system and see what we find.
Thanks again!
 
Just take the gas cap off and run it. That will easily ensure the tank is venting.
I did just that today......cap off.....no moaning. Cap on tight.....it moans again. It would appear to be in the venting system. I checked the vent system diagram and it appears to be plumbed in correctly. As far as I can tell, the valves appear to be in the right direction. One of the valves is a new one from MWB and the other is from the donor car that the engine came from. Maybe it is faulty?
At any rate, Thanks to all for your input.
 
tried to inject some low pressure air (10PSI) into the hose down along the frame, where ambient air is drawn into the tank to equalize pressure. Duplicated the moaning sound, close, but not exactly the same sound. The valve in that line MAY be in backwards, but it appears to be correct according to the diagram. Possibly a faulty valve? At least I think we are on the home stretch!
 
Problem Solved! We had the valve going to ambient air in backwards and the Y junction with the orifice installed incorrectly. Matt from MWB sent us a photo of the system hookup which was much clearer than the diagrams in the service manual and the North American Fiat "intro to the fuel injected X1/9". No more moaning
 
This sounds to me like a problem with the tank venting system. Are all the bits and pieces of the evaporative emissions system still present? As you draw fuel out of the tank, air must be allowed to come in and replace it. There is an elaborate system of hoses, valves and separators for this purpose. Every so often something gets clogged, or someone gets a bit over eager in de-smogging a car and plugs the system.

Have a look at the FSM in the Wiki (page 10-108) and see if your evap system matches the book. Are all the hoses connected where they should be? any of the hoses clogged? Items 8, 9 and 10 operating as they should?
Winner!
 
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