Diesel Leak at Fuel Gauge

[Tmacmi]

While digging in the engine bay I found this. I appears to be leaking from bad gaskets. I've already emailed Moeller to ask about replacement gaskets.

I have a couple quick questions before I start pulling this apart.

1) do you believe those nuts go into a threading in the tank itself or do you think there are loose nuts underneath. (which would be unfortunate)

2)I'm wondering if a clogged breathing hose would be a contributing factor. Any way to check? A long snake?

[mike d.]

If Moeller is the mfg they would be able to tell if there is a metal flang/disk bonded inside ! From the pic it would seem that there must be something inside! The chance is those are self tapping screws ! You could try snugging them a little ! If they are self tappers, you can make a metal ring with same bolt/screw pattern, I would thread those holes for machine screw the same as for the original 5, then drill to small retaining screw holes, match those 2 holes, and cut it in 1 spot, so you can twist it inside, hold in place with retaining screws, then just put on gasket,and put sender back on ! All done! I did this to my fiberglass iank in our Gulfstar 37 because the inspection plate was seized in the mounting ring! Worked out well !

[a64pilot]

Yes a clogged vent could certainly do it. A way to check is to blow air from a Vacuum cleaner etc into the tank fill if it’s not clogged, mucho air will blow out of the vent, you can do the same with a dinghy pump too.
Don’t use a vacuum on a gas boat, that motor sparks a lot.

On my boat you check the vent when you fill it up. When it’s full a bit of fuel spits out of the vent. Of course that’s a no no, but most all boats do.

There is even a whistle you can put in a vent hose, when it stops whistling when your filling, stop, fuel just hit the whistle.

[sailormed]

On my moeller tank all bolts were into copper/bronze inserts.
I use Hylomar Bleu sealant for the diesel tank.

[Tmacmi]

Originally Posted by sailormed

On my moeller tank all bolts were into copper/bronze inserts.
I use Hylomar Bleu sealant for the diesel tank.

I was able to look at one of the photos. The tank is a Tempo tank. There is not much for it but to hope that the tank was tapped, had inserts or welded nuts inside.

I'm working with Moeller. They only have gaskets for between the flange and the tank, not between the sender and flange. I'll have to replace the whole thing. I'm now trying to figure out what the replacement part might be.

[Bill O]

Originally Posted by Tmacmi

I was able to look at one of the photos. The tank is a Tempo tank. There is not much for it but to hope that the tank was tapped, had inserts or welded nuts inside.

I'm working with Moeller. They only have gaskets for between the flange and the tank, not between the sender and flange. I'll have to replace the whole thing. I'm now trying to figure out what the replacement part might be.

Not sure why you would need to replace anything unless it not working. Maybe the vent was clogged, maybe you overfilled the tank. Would try the vent first and clean up the area to see if its still leaking.


Bill O.

[a64pilot]

It’s not hard at all to cut your own gaskets. I’d just go to a parts store and get me a small sheet of rubber gasket. Cork would work, but I prefer rubber for this.
I’m not one for sealant though, but if you feel you need to go that way, be sure it is fuel proof. For instance silicone is not.

[Boatwright]

Originally Posted by a64pilot

It’s not hard at all to cut your own gaskets. I’d just go to a parts store and get me a small sheet of rubber gasket. Cork would work, but I prefer rubber for this.
I’m not one for sealant though, but if you feel you need to go that way, be sure it is fuel proof. For instance silicone is not.

Good advice. Don't try and run the screws through the gasket without punching holes first -- a leather punch works well -- otherwise you will end up with a raised ring of gasket material around the screw, making it hard to get a good seal. Also use Buna-N closed cell nitrile rubber -- neoprene will deteriorate. McMaster-Carr #9023K22

I'd start by removing one screw to see if it's a machine thread or a sheet metal screw. If the former, it's likely there is extra metal thickness around the hole. In any case with a proper gasket you do not need to overtorque the screws and strip out the hole.

[donradcliffe]

The tank is probably not tapped--the metal is too thin.

In my experience, there is a horseshoe shaped backing plate that is tapped for the five screws. One of the screws is longer than the others. You back out all but the long screw, and loosen it about 1/4 inch. Then the backing plate swivels and can be drawn out of the hole.

How do you figure out which is the long screw and how far you can safely back it out??

VERY CAREFULLY.

[Tmacmi]

Originally Posted by donradcliffe

The tank is probably not tapped--the metal is too thin.

In my experience, there is a horseshoe shaped backing plate that is tapped for the five screws. One of the screws is longer than the others. You back out all but the long screw, and loosen it about 1/4 inch. Then the backing plate swivels and can be drawn out of the hole.

How do you figure out which is the long screw and how far you can safely back it out??

VERY CAREFULLY.

That is what I've been concerned about from the beginning. I have some hopes from an earlier poster's experience that there may be copper bronze inserts.

[Pete7]

Some of those tank gauges have slightly offset screws and matching gaskets, so that the sender only goes in one way Took a while to work out why the screws didn't quite line up the first time I took one apart. Use a blob of paint to show how it lines up on the tank before taking it apart.

Pete

[a64pilot]

Originally Posted by Pete7

Some of those tank gauges have slightly offset screws and matching gaskets, so that the sender only goes in one way Took a while to work out why the screws didn't quite line up the first time I took one apart. Use a blob of paint to show how it lines up on the tank before taking it apart.



Pete

That is common and I’ve wondered why. I believe it’s to keep a well meaning person from accidentally installing it with the float against the tank wall or something.

I’ve never personally seen the long screw thing myself, but removing and installing a couple at a time should easily identify the long one.
I’ve never seen a ring on the inside that could fall either, but if that’s possible then threaded rod should make it so you can hold the ring in place, just two pieces of long threaded rod and of course vise grip the rod when the sender is above it.

I can’t imagine how it could be done with individual nuts from underneath, that would require it to be installed before the tank was welded up?

[donradcliffe]

Its not that bad unless you are in the bush. Just take one screw out at a time until you find the long one. You can always buy a new backing plate if you drop it.

[JPA Cate]

From just looking at the photo, I was thinking the black piece for the sensor looks moist. If your finger comes up dieselly when you touch it, maybe it is just the sensor mounting that is loose, not the whole lot. If so, just tighten the loose part, and if it needs sealant, go for it.

Once had to fix a leaky fuel gauge under way, used marine tex around the edge, and it worked fine, was still working 15 years later, when we sold the boat.

Ann

[Cheechako]

If you can replace that rubber gasket with rubber impregnated cork. Far better. The rubber gets slippery with diesel and the more you tighten the more it extrudes out.