Replacing Wema Fuel sender in LM27
Nov 6, 2022 18:19:02 GMT
Post by tonyp on Nov 6, 2022 18:19:02 GMT
If you want to replace a sender like a Wema S5 without disturbing the tank inspection cover, this might help. It won't apply to senders that are threaded into a base plate that's permanently fixed to the tank top.
The problem with senders like the Wema, as fitted to our boat, is that they are secured by screws through the inspection cover into holes tapped in a steel ring on the underside of the cover. Unfortunately, this ring is not attached to the cover, so when you unscrew the sender to replace it, the ring drops into the bottom of the tank! To remove the sender but not lose the ring, simply replace one of the sender's fixing screws with a long one. Wema's use m5 machine screws and a 50 or 65mm long M5 screw works well. Only screw it a few turns, but make sure it's properly into the ring, then you can remove all the other screws (which are 25mm) leaving the sender attached to the ring by the long screw. You now have space between the sender and the tank to get hold of the ring with a bit of hooked wire or your finger before removing the long screw and the sender. I'd suggest then tying the ring on with a bit of string!
To fit a new sender you have to get the holes in the sender, the tank top and the ring all in the same position - and they are not evenly spaced around the ring! So get the ring into the right position with a finger (leave the safety string on) then, with a long screw in the new sender, fit it into its respective hole in the tank and ring. Again, only give it a few turns just to capture the ring securely. The ring will probably move during this operation so you'll need to re-align it to fit the next screw. The long screw gives you space between the sender and the tank to get your finger in the tank and juggle the ring into position. A nail in one of the other holes in the sender will help align and retain the ring's position. When you've got everything lined up again fit a second long screw into the sender and then screw it into the ring. Once you've got the two screws in you can remove the safety string and tighten the sender down snugly, but not tightly. Once the sender is in place fitting the remaining screws is straight forward. Finally replace the long screws with the correct short ones.
I learnt this lesson after the previous owner's fitters dropped our ring into the tank when changing the fuel sender. Instead of getting it out again they tried to secure the sender with self-tappers, which couldn't, and didn't work. We always had diesel leakage from it. I only discovered this when I drained the tank to clean it and found the ring in the bottom!
Tony
The problem with senders like the Wema, as fitted to our boat, is that they are secured by screws through the inspection cover into holes tapped in a steel ring on the underside of the cover. Unfortunately, this ring is not attached to the cover, so when you unscrew the sender to replace it, the ring drops into the bottom of the tank! To remove the sender but not lose the ring, simply replace one of the sender's fixing screws with a long one. Wema's use m5 machine screws and a 50 or 65mm long M5 screw works well. Only screw it a few turns, but make sure it's properly into the ring, then you can remove all the other screws (which are 25mm) leaving the sender attached to the ring by the long screw. You now have space between the sender and the tank to get hold of the ring with a bit of hooked wire or your finger before removing the long screw and the sender. I'd suggest then tying the ring on with a bit of string!
To fit a new sender you have to get the holes in the sender, the tank top and the ring all in the same position - and they are not evenly spaced around the ring! So get the ring into the right position with a finger (leave the safety string on) then, with a long screw in the new sender, fit it into its respective hole in the tank and ring. Again, only give it a few turns just to capture the ring securely. The ring will probably move during this operation so you'll need to re-align it to fit the next screw. The long screw gives you space between the sender and the tank to get your finger in the tank and juggle the ring into position. A nail in one of the other holes in the sender will help align and retain the ring's position. When you've got everything lined up again fit a second long screw into the sender and then screw it into the ring. Once you've got the two screws in you can remove the safety string and tighten the sender down snugly, but not tightly. Once the sender is in place fitting the remaining screws is straight forward. Finally replace the long screws with the correct short ones.
I learnt this lesson after the previous owner's fitters dropped our ring into the tank when changing the fuel sender. Instead of getting it out again they tried to secure the sender with self-tappers, which couldn't, and didn't work. We always had diesel leakage from it. I only discovered this when I drained the tank to clean it and found the ring in the bottom!
Tony