SECTION 21: Fuel Sender Assembly
Jump to navigation
Jump to search
Before you start:
Build Instruction Updates
- Check for more recent updates here
Videos
- Sealing the Fuel Tank – Playtime with Pro Seal (Episode 9) — Average Joe's Airspeed Acres
Modifications to Consider
Special Tools / Supplies
- B2 fuel tank sealant (sender flange and QB tank closeout)
General Build Notes
- QB builders — W-15040 cover plate count: Very early QB tank kits may have only 16 W-15040 cover plates instead of the required 24. The extra 8 are needed for tank closeouts. Contact Van's if short — they will send replacements.
- Fuel Cap Count: Very early QB tank kits may have shipped without fuel caps. Contact Van's if short.
- QB tank pre-seal inspection: Before sealing, inspect and clean tank interior with a lint-free cloth and isopropyl alcohol. Test the fuel sender float arm through its full range by tying a string to the arm and pulling through the inspection hole — confirm no binding against the tank bulkhead. Leave covers clecoed until ready to permanently seal.
- Cover plates and senders — sealing process: The kit's tank hatch nutplates are not the sealed type, so the seal is made by the assembly process. A proven sequence: scuff both surfaces with Scotch-Brite and clean, Proseal both the flange and the cover plate, dip each screw in Proseal before inserting, then torque in an opposing-side sequence — a Proseal ring should squeeze out around every screw. The same process (minus the rubber gasket) applies to the sender. Proseal does not lock the screws; removal later needs no extra torque. For routine interior inspection you don't need to open a cover at all — removing the sender leaves a big enough hole for a borescope. Source · removal · borescope
Revision History
- R0 - Initial release to builders
- R1 - Not released.
- R2 - Full re-issue (08/17/26). 16 -> 20 pages; completed assembly renumbered T-15509 -> T-15511; parts list 15 -> 17 rows adding 52x AN426AD3-3.5 and 26x K1000-08D per side; new nutplate pages 21-14 to 21-16; leak testing moved 21-14 -> 21-17; right wing sender orientation (180 degrees) documented on 21-09.
Specific Build Notes:
Page 21-06 (R2)
- Lighted extendable shop mirror (or borescope) is recommended for interior inspection; mask all openings after cleaning as additional technique for added FOD prevention.
Page 21-09 (R2)
- Float wire bends: At least one builder found the bend dimensions given in the KAI were not accurate and had to add roughly 1/2" to each length before the float would sit correctly. Check the fit against the 1/16" travel limits rather than trusting the printed dimensions. Sanford EAA log, Jul 12 2026
Page 21-09 (R0) - Corrected in R2
- This is now a Note on R2. Setting the float: aim for 1/16" gap at both extremes; a tongue depressor makes a workable feeler gauge. If the top gap can't be achieved the gauge will read full until initial burn-off.
- This is now diagramed on R2. FUEL SENDER ORIENTATION — RIGHT TANK: Kits ship with two IE F-385B senders (same part number). The right tank requires a different orientation to align screw holes. Installing right-side-up on the right tank results in the holes not aligning. Flipping it upside-down works for hole alignment, but the float arm geometry differs and clearance to the nut plate may be an issue — bend the float arm as needed and verify clearance through full float travel. Note: modern EFIS systems (Garmin G3X, Dynon SkyView, AFS) can calibrate regardless of resistance sweep direction. Analog gauges will read backwards on the affected tank unless the sender is correctly oriented. Contact [email protected] if you received two -385B senders and need a -385C for the right tank.
- Not recommended to purchase with R2. The correct right-hand sender can also be purchased directly from Stewart-Warner.
Page 21-11 (R2)
- KAI erratum — page 21-11 (R2): Item 8 (AN526C832R6, 48X) appears in the parts list and figure, but not called out in Step 3.
- Step 1. in RO was removed, to scuff and clean the mating surfaces.
Page 21-12 (R2)
- KAI erratum — page 21-12 (R2): Step 1 reads "Install (1) into (2)", but the page's parts list only contains items 2 (fuel cap) and 3 (tank subassembly). It should read "Install (2) into (3)".
Page 21-13 (R2)
- SA187 drain valve - thread engagement in the VA-112: Several builders found the SA187 would only engage a turn or less by hand, or would not start at all. Pipe threads should engage at least four threads when tight; one builder slowly enlarged the VA-112 hole until he could turn it in four turns by hand, then applied the 1.5-2 turns past hand-tight from Section 5. Do not over-tighten - the VA-112 can crack or split. Source
Page 21-14 to 21-16 (R2)
- New in R2 — nutplate installation (pages 21-14 to 21-16): R2 adds work that did not exist at R0: 26x K1000-08D nutplates and 52x AN426AD3-3.5 solid rivets per tank. If your inventory didn't include them, request the 52x K1000-08D and 104x AN426AD3-3.5 from Van's. Supporting math: QB Wing · SB Wing.
Page 21-17 (R2)
- Camco HVAC leak-detection fluid works better than soap-water (rocketman1988). Herbert found a small leak at a lower inboard corner rivet (Jun 15) — corner rivets are the place to look.
- Balloon in the KAI setup only prevents over-pressurization — it only reveals large leaks. Additional opinions available in Fuel Tank Testing Thread.
- Manometer testing: Alternate to balloon, or if leak is suspected: 0.8-1.0 psi held on both tanks simultaneously, monitored for 90 hours to a month. Expect a small apparent leak-down (~0.01 psi/hr initially, tapering) - over long runs, correct for temperature and barometric pressure before concluding you have a leak, and tape all connections. Filling with fuel also works but leaves the upper-skin rivets unsubmerged (~29 gal per tank). Source - 1 psi / one month - leak-down data
- Leaks found in practice: one builder's leak was a rivet on the top of the tank - replaced, retested, passed. Combined with the earlier lower-inboard-corner rivet report, check rivets before assuming a seam problem. Herbert EAA log, Aug 1 2026