Fuel sender mounting and modifications

After studying the VDO brackets as suppled, it is clear that the manual get the location of the chamfer (in the sender mounting plate) wrong. Rather, the rubber washer should be trapped between the sender mounting plate and the (Sling supplied) sender mounting arm, and the chamfer should be applied to the latter, similar to the VDO supplied part.

So I chamfered the sender mount arm to a degree similar to the VDO counterpart.

There is also the problem of achieving a reliable ground connection to the sender mounting plate and arm. Some builders trap a lug or spage connector under a rivet head or tail, using an additional hole. I found that such a method did not retain a lug particularly securely. Held under a rivet head, I was able to rotate the lug with finder pressure. Given that the relevant resistanced being measured range down to 8 ohms, any such movement could lead to progressive loss of a reliable low resistance connection.

I decided instead to replace the rivets holding the sender mount arm with bolts. These bolts screw into trapped rivnuts. Using a 10mm counterbore a recess was made just deep enough to allow the rivnut head to sit very slightly proud of the surface ensuring that it would be compressed somewhat when the bolt is tightened ensuring a good torque-handling capability. A lug can then be trapped under the bolt head with much greater firmness than the other methods.

Tank sealant was smeared over all the bushings, washers and surfaces on assembly. Tank sealant was also formed into a blob over the rear of the rivnuts. The 4mm bolts were secured using loctite 577 (will change to 243 or 277). Mild steel washers were used on the VDO bushing bolts. 304 stainless steel washers were used with the ground lugs, smeared with Duralac yellow