Fuel gauge

[bugbitten]

I'm still working on getting all my gauges working. Right now, I'm struggling with my original fuel gauge. The tank sender was shot, so I ordered a new Wema unit; however, no matter what I do, I only get a full reading when on and empty when off. I'll attach a shot of the connections at the back of the gauge. Based on the original connections (and logic), it seems the center post is 12V in, the left post, marked "S", goes to the center, and the right post, marked "I", goes to ground. I've tried this with the original wiring (which all tests good), and on the bench at home. Regardless of whether the sender is connected to the "S" post, the gauge pegs on the full side as soon as power is given to it (I've slid the float up and down, with no change). I'm grounding the other sender connection to the same point as the gauge.

Time for a new gauge, or am I doing something wrong? The pointer moves in a very nice, dampened way, toward "E", when power is removed, so I thought there was hope for it.

 

[Stu Jackson]

"I" usually means ignition, and, thus, (+) power, not ground.

Here's a Teleflex tach wiring manual: http://c34.org/manuals/S024.pdf

Try Googling Teleflex and find more diagrams and instructions.

 

[bugbitten]

"I" usually means ignition, and, thus, (+) power, not ground.

Here's a Teleflex tach wiring manual: http://c34.org/manuals/S024.pdf

Try Googling Teleflex and find more diagrams and instructions.

I had thought that "I" was power initially, but when I connected my DMM to it and the unlabeled post, I got a negative voltage reading. I'll try it the other way, just in case (again, I got these results with the original wiring, untouched, except for the sender wire going to the new sender).

Just back from picking up my modified Hitachi alternator, so I should be connecting my Teleflex tach later today!

 

[bugbitten]

You were right! I just reversed the connections, putting power to the "I" and ground to the unlabeled, and it works perfectly. It's good, I guess, to be the one guy everyone else can feel smarter than!

Now if you can just help me figure out how to back the damned boat to starboard!

John

 

[bugbitten]

The fuel gauge is back in the boat and working great. Alas, a new problem has arisen: at least two and probably three of the bolts that hold down the fuel tank sender won't tighten. I'd say two were already stripped and one let out its last gasp as I was gingerly tightening it. Two tightened well, but they're adjacent, so not much reassurance that it won't leak in rough conditions (or admit moisture even in mild ones).

It's an aluminum tank, which I'd rather not have to replace just yet. I thought I could try to reverse the loose bolts, and send them up from inside the tank. Then I'd fasten them down with nuts on the outside, but getting my hand in that small opening is unlikely. Other suggestions? Tap for a larger bolt?

John

 

[Maine Sail]

I'm still working on getting all my gauges working. Right now, I'm struggling with my original fuel gauge. The tank sender was shot, so I ordered a new Wema unit; however, no matter what I do, I only get a full reading when on and empty when off. I'll attach a shot of the connections at the back of the gauge. Based on the original connections (and logic), it seems the center post is 12V in, the left post, marked "S", goes to the center, and the right post, marked "I", goes to ground. I've tried this with the original wiring (which all tests good), and on the bench at home. Regardless of whether the sender is connected to the "S" post, the gauge pegs on the full side as soon as power is given to it (I've slid the float up and down, with no change). I'm grounding the other sender connection to the same point as the gauge.

Time for a new gauge, or am I doing something wrong? The pointer moves in a very nice, dampened way, toward "E", when power is removed, so I thought there was hope for it.

"I" is ignition switch ON and is +. "S" is the sender from the WEMA gauge which is a pink wire. The grounds are the two nuts touching the metal plate that grounds the light bulb which is missing... Where are you wiring the ignition/12V wire too?

The WEMA gauge does not and should not have 12V flowing through it. They read resistance 33 Ohm's to 240 Ohm's.... Only the gauge gets 12V power through the "I" terminal. I hope you did not toast the sender or the gauge but the gauges are cheap...

 

[Maine Sail]

The fuel gauge is back in the boat and working great. Alas, a new problem has arisen: at least two and probably three of the bolts that hold down the fuel tank sender won't tighten. I'd say two were already stripped and one let out its last gasp as I was gingerly tightening it. Two tightened well, but they're adjacent, so not much reassurance that it won't leak in rough conditions (or admit moisture even in mild ones).

It's an aluminum tank, which I'd rather not have to replace just yet. I thought I could try to reverse the loose bolts, and send them up from inside the tank. Then I'd fasten them down with nuts on the outside, but getting my hand in that small opening is unlikely. Other suggestions? Tap for a larger bolt?

John

You can tap for larger bolts but this will require over drilling the sender plate too. The WEMA's use stainless. The problem with this is that the machine screws that come with the sender have a special gasket applied to them. Option two is the rotate the sender and re-drill & tap for the factory WEMA screws. Be careful to not go to happy with the tap. Many of these tanks were built of the bare minimum thickness of .090 wall...

What ever you do DON'T drop a stainless screw into the tank. It can eventually eat through the aluminum..

 

[bugbitten]

Luckily, I don't think I ever ran power through the sender. I just (and I think the PO) had the power and ground wires reversed. All is working perfectly. (I've got the bulb pulled to test it.) Those Wema folks, BTW, were very helpful. I'd misplaced the instructions and they sent me .pdf replacements pronto. Those say, oddly enough, that the pink wire is the ground and the black goes to the sensor, the opposite of what I'd thought. I'm looking forward to needing something else from Wema in the future.

I'm not keen on trying to drill and tap new holes, given the limited access and my somewhat limited, sixty-two-year-old flexibility. Maybe I should just use the fuel up, bite the bullet, and haul the tank out. Some folks are saying 30 years on an aluminum tank is pushing it.

John

 

[BobM]

Take a clean cloth an wipe under the front of the tank facing the engine. If it smells like diesel...its has to go...or you will get to clean diesel out of your bilge like I did. No fun. Mine had pinholed along the front weld as well as under the bottom of the tank where the mounting straps contacted the tank bottom. Do yourself a huge favor. If you pull the old one don't put it back in. A plastic replacement is about $100.

 

[bugbitten]

Thanks, Bob. I knew you'd replaced yours. If I pull it, it's definitely not going back in. I'll try the rag test and see how it looks. I'm thinking it'll give me better access, while it's out, to the rusty hot water heater. It'd be nice to replace that at the same time.

John

 

[BobM]

I wish. The previous owner yelled it patched it and put it back in. I view it as a ticking time bomb. My fresh water tank is leaking and I hope to do it this season and perhaps the fuel tank next season. It is easy to get behind on maintenance.

 

[bugbitten]

I thought it was normal to be behind on maintenance. But hey, I've cleaned my Racor, fixed my fuel leak, replaced the camshaft seal, got a working fuel gauge, temp gauge, and tach for the first time, so some progress! I picked up some slightly-larger screws for anchoring the fuel sender. I'll see if they buy me some time. Maybe I'll actually get to sail soon!

Not to hijack my own thread, but what are you using for batteries? I've only got two, and I'm thinking about upgrading and going to two house and one starter.

John

 

[bugbitten]

I picked up some stainless #12 x 1" sheet metal screws to use to seat the fuel tank sender more securely. As mentioned above, the original bolts would no longer tighten. The new ones will fit through the Wema sender's openings, but are enough bigger than the original screws that they snug down nicely. Is it okay to use stainless fasteners on an aluminum tank, or should I switch to something else?

John