Sean I was initially hesitant to believe there was no valve on that block until I decided to go into Alldata on my shop account and poke around in the description and operation section of the fuel system and youre right it clearly states a check valve inside the tank. Here is Alldata's direct copy and pasted information....... Fuel Pressure Check Valve Description and Operation
Description and OperationNotesPURPOSE
Maintains fuel pump prime and fuel supply line
pressure after engine is shut down.
The check valve, normally closed, opens when the outlet pressure from the energized pump exceeding the opposing check valve spring force.
***AND THERES EVEN A RECALL FOR THE GAS ROLLING OVER FROM ONE TANK INTO THE OTHER.****
Recall - Cross Tank Fuel Flow ConditionNotes
RECALL NUMBER: 93S68
Date: Sept. 1993
At Dealers By as Req'd.
At PDC by
Date in Owner Letter
0% of Parts Direct Shipped to Dealers
TO: All Ford Dealers
Safety Recall 93S68 - All 1990, 1991, 1992 and certain 1993 Model Year F-Series Vehicles equipped with 4.9, 5.0, 5.8 or 7.5 Liter Engines and Dual Fuel Tanks
All 1990, 1991, 1992 and certain 1993 model F-series vehicles equipped with 4.9, 5.0, 5.8 or 7.5 Liter engines and dual fuel tanks
REASONS FOR RECALL
Some of the affected vehicles may experience a cross tank fuel flow condition due to a damaged check valve in the fuel pump/sender assembly. Fuel may be supplied from one tank and some or all of the unused fuel may be returned to the other tank. Should this occur, the capacity of the receiving tank may be exceeded and fuel may overflow from the filler cap. Fuel spillage in the presence of an ignition source could potentially result in a fire.
To correct this condition, the fuel pressure regulator will be replaced and a check valve will be installed between each fuel supply line
and fuel tank
FREE FUEL LINE REMOVAL TOOL
Standard fuel line removal tools can be used to disconnect fuel lines. However, because of the number of vehicles to be serviced, two free tools (# T93T-9550-AH) will be provided to each Ford dealer. These tools will be in your next Dealer Mail System (DMS) shipment (DMS packing slip # 930902).
***AND THE CHECK VALVE IS INSTALLED AT THE END OF THE LINE ON THE PUMP INTSELF. THE TECNICAL LETTER DID MENTION NEW LINES THAT HAVE CHECK VALVES BUILT INTO THEM. GEUSS I NEED TO RUN MY VIN AND SEE IF ITS BEEN DONE CAUSE I DONT HAVE ANY SMALL VALVES AT THE TOP OF THE TANK LIKE IN THIS PICTURE.***
11.PRE-POSITION THE SECOND SAFETY CLIP ON THE OTHER END OF THE CHECK VALVE CONNECTOR (IF NOT ALREADY PRE-POSITIONED - SEE NOTE IN STEP # 10).
**I copy and pasted the entire section with pictures into this post right off alldata and it displayed it in my computer screen after posting and when I logged in from a different computer I dont see any pictures, sorry guys, if anyone knows how to fix this feel free to let me know.**