Download Torque Pro from the Play Store on his (or your) Android phone. (If you don’t have one – pick up a old used Android phone or tablet – as long as it has working WiFi and Bluetooth, you don’t need to register it). Then get a Bluetooth dongle off Amazon to plug into the Winnebago OBDII diagnostic port. You will then have the ABSOLUTE BEST code reader / scanner / logger on the market – all for less than 50 bucks if you have an android device. If not you can pick up a used one for a few dollars more. Since it is a Ford V10, I would install the Ford Extended PIDs during setup (as there probably aren’t a set for ‘Winnebago’).

Your Fuel tank is not holding vacuum when draw down is attempted by engine vacuum via the Electronic Vapor Management Valve (EVMV or Purge Valve) – located somewhere on the ‘firewall’—OR a bad Fuel Tank Pressure Sensor – located somewhere on tank or fuel supply line.

If your gas cap is on good and tight (I assume he has replaced it already), check for (large) air leak in the Fuel Tank System somewhere. (Duck Tape a shop vac output to tank filler neck and ‘listen’ – spray soap/water solution on everything associated. Might have to make a cheap ‘smoke’ machine.)

Fuel tank pressure sensor outputs voltage inverse to vacuum (probably from ~ 2.5 volts with ambient pressure {Cap Off}, own to 0.50 volts at full engine vacuum). But all that, and its location is above my pay grade completely on that vehicle.

BTW. Thank you Husband for his service.

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