Join Date: Aug 2009
Location: Lakewood, Colorado, USA
Model: '06 GL1800
If the filter is empty, then you're likely looking at the pump or its circuit. If you're getting the longer rides out of it while the tank is fresh and full, then I'd jump to the conclusion that the pump and/or its strainer is suspect.
The Petcock comes after the pump, so shutting it off while the pump is running will generally leave the filter full as your carbs starve for fuel.
A stopped-up cap would leave a vacuum in the tank and an empty fuel filter when your pump could no longer pull strong enough to overcome the vacuum in the tank. Open the gas cap, you'll be able to feel the vacuum (cap kinda sucks in), then try to start again while you watch the filter (with the cap still off) - if you get pump-action and a start (will take a bit to refil the floatbowls), thn your cap is suspect.
The filter media is on the outlet side of the filter housing, so if the filter is plugged (and the pump running) you'll have a full-looking filter while your carbs starve.
There is an Airtex (aftermarket car-part) pump that can save a few $$$ on replacing the pump, if you're not already too far down that road...
You could bypass the fuel-pump cut-off relay and/or the BAS to see if you run well that way (typically, a failing BAS will allow you to restart as soon as you've cycled the ignition key fully off, then back on; similarly, the "typical" fail mode for the relay is to fail on shut-down and not 'pull-in' for the next start.)
Each time you turn the ignition key to the "run" position, the fuel pump should run for about 1-2.5 seconds. If you bring some 3/8" fuel line with you (for your next failure) you could use this feature to check for proper output from the pump pull the outlet side of the fuel filter, conenct your "spare" hose there and run the other end back into the filler hole (gas cap), then turn the key to run... You should hear the relay click and the pump humm for a second or so; fuel should flow outta the hose (not like a garden hose, less than a half-cup total). May not help much, but it'll give you a look to see if your pump and control circuit is working at that exact instant.