Vans Fuel gages

Got a problem with my Vans right Vans fuel gage. When I hit the engine starter, the right fuel needle immediately pegs on zero. Used to be I just turned off the master switch for a sec, then back on, and the fuel needle would come back up. That's not working anymore. I didn't build it and the mechanic is looking for wiring diagrams. The only thing I can find in the Vans building manual is a "sample" wiring schematic "
for RV aircraft" on the last page (it's not numbered) just before Section 6-The Empennage.

Can anybody help??

Check to make sure that the fuel probe sender is grounding to the airframe. Some builders have had to add a ground line on one of the screws holding the sender in place to get a good ground.

I have the same problem with both my Vans fuel guages. When the master is first turned on, both gauges always indicate correctly. When the starter is engaged, one or both gauges occasionally latch on empty and stay that way. Recycling the master, has always returned gauges to normal and and they continue to work through the rest of the flight.

Here are some data points. The problem is aggrivated with full fuel in the tank and dissappears with low fuel.

Adding grounds to the tank senders did not help.

With the gauges in the failed mode, momentarily disconnecting then reconnecting the sender wire also makes the gauge start working.

I've come to believe my Vans fuel gauges are sensitive to battery voltage. During engine start, bus voltage drops and the gauges sometimes latch on empty. I put a peak detecting voltmeter on my bus during engine start and recorded bus voltage as low as 8.2 Volts during engine start, even with a brand new fully charged battery.

At this point, it's been a minor annoyance because it's occasional and recycling the master has always fixed it. I've thought about buying another pair of gauges but I have no reason to believe that will fix the problem.

Anybody else seen this or fixed this problem?

My RV-6 was bought flying last summer (7/09). It was completed in '06. I had very similiar fuel gauge behavior to Brad - when the master was turned on, they worked fine. After engaging the starter one or both would read zero. Recycling power to the gauges fixed them for the remainder of the flight. Initially I did not think the battery was weak/dying (used to old Cessna). Finially did replace it about two months ago, and along with much faster cranking, the fuel gauges now work 100% of the time.