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Hello again.
Now that I have my boat back in my own hands (with lovely new Volvo engine) I have started to sort out the numerous issues which come with an older boat.
High on the list is the fuel tank gauge, the needle of which has not moved in the three months I have had the boat. Probably the sender gone bad. Are these "standard" units? I have to cut away some of the sub flooring to get the old one out, but thought I'd ask the experts what to expect and where to get a replacement.
Any tips?
Thanks in advance
Bob
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Your fuel sensor is going to be at the base of the ladder. On the DE38, you can pop the lower section off and you should be able to find the top of the fuel tank. On the fuel tank there is a circular access with four to eight screws around the circumference. That is the fuel sensor float.
After you've done the obvious checks ensuring that the electrical connections are tight on the sensor. Get yourself a multimeter, and check that there is a voltage on the sensor. I believe the voltage should be positive on the nut connecting the wire, and the tank should be grounded/neutral (black probe to tank, red probe to nut). When the panel is on, it runs a low current through the sensor and the sensor becomes either more or less resistive as fuel rises or lowers in the tank. That low current drives a motor in the fuel gauge, which tells you how much fuel you have. If those wires are crossed, I wouldn't be at all surprised if the gauge is buried at "E".
You can pop all of those screws off which are holding the sensor in place, and should be able to pull out the fuel sensor for the tank. The first thing to check is if the sensor is operational, and the easiest way to do that is to flip the panel on and manually run the fuel sensor and see if the dial reads. Sometimes they may get stuck in the tank and they just need a bit of wiggle to get them loose. My boat draws fuel so slowly, and we use the engine so infrequently and for short runs, I arrived at the erroneous assumption it wasn't working when in fact it was perfectly fine, I just never noticed it. As usual, when dealing with fuel fumes take extra care not to send yourself into low-earth orbit by lighting a smoke while you've got an open tank full of dead dinosaur squeezings.
Check the sensor to the bench, put it on a multimeter and see if its resistance changes as you move the float. If the sensor does not change the resistance as the float moves you know the sensor is bad. Replace it, they're cheap. If the sensor tests good...I'd still replace it. They're like $30, and keep the old one as a spare. An old sloppy worn out sensor is better than no sensor if you're 300 miles offshore and need to know how much fuel you have left.
If all of that fails, check that there's a voltage on the gauge itself. There may be a break in the wiring run between sensor and the gauge. If you get a voltage, you know it's the gauge and you need to replace that. If it's go no signal, then you've got to try to find where the break in the run is.
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Many thanks, Patrick. I am away from the boat for the next three weeks, so can't use the multi meter. But I have a photo and see two problems right away. First, there are only two wires connected. One in the center and one on the edge. But there is a third terminal on the opposite edge, but no wire! Should there be three connections? Second, the floorboard covers a good part of the sender so I'll have to chip away part of the board to get to sender out. Not a problem, but I can't do that right now. Will report back when I can get to the boat again.
Cheers
Bob
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You should be able to pull the sensor out without having to chip away, unless somebody has done a wacky repair in the past. There was only two wires on mine, not three. It's a very simple sensor.
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Good to know about the wires. I'll have to get it out to be sure.
I Do have to chip out a bit of the sub flooring where it covers part of one screw head.
cant wait to get home and get to work.
vacations can be a drag!
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Well, I finally got access to the whole flange for the fuel gage sensor assembly and pulled the mechanism out. I was surprised at how long it is. There is about 2 ft of rod (holding the wire to the gage) going down to the articulating/sending device and then a long (maybe 18 in) wire holding the float. I wonder if that is the original unit. I have found similar units on the internet, but wonder if I should get precise dimensions of the existing set before ordering. The dial still is stuck on 3/4 full as it has been as long as I have had the boat, so I guess it's toast. Now to select the right stuff.
Once I get a compatible gear, how do I orient and calibrate it? I assume that the long wire with the float should be aligned fore and aft, but what about vertical alignment? Does anyone have a drawing of the layout?
Many questions, but happy to see what I am working with.
Bob
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Reviewing the senders I can find on the 'net I am slowly getting the picture. The long arm gets the sender and the float (with wire) down towards the bottom of the tank. I guess that the angle between the wire holding the float and the vertical arm will be about 90 degrees when the sender says "E". Then as the float rises the sensor says, 1/4, 1/2, 3/4, F. My owner's manual says that then the gage says E there still should be 15 gal in the tank. Rather obvious, Dear Watson.
So to proceed with the repair I just have to get a thin stick to see how deep the tank is and then get a fuel level sender of the appropriate length.
I'll see if I can test the gage itself as well. As Patrick says, it may just be a broken wire.
At least it looks completely do-able. Will report back on progress.
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I just posted the results of my "survey" of my fuel tank on another thread. My confusion is in the size of the tank.
My measurements show about 35 gal whereas the owner's manual says its 60 (plus a reserve of 15) gal.
The amount is not so important as knowing how to set the fuel gage that I am about to install. It is adjustable in height so I want it to read Empty when the main volume has been used and the engine is about to use up the reserve. It seems that this would be at a depth of 12 inches. I'll go back and do my survey again. Of course I can change the level of the sender any time in the future (as long as I don't cut off the "excess" rod. I guess I am just venting my frustration rather than asking a question, but if anyone has more insights on the size of these tanks please let me know.
Bob
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Where is the other thread?
All I can say is that the goofy shape of the DE38's fuel tanks makes it almost not worth trying to figure that out. I know from the floor to the bottom of the keel you're looking at 2 - 3 feet, and the sharp dropoff of the tank is probably half that. My replacement tanks are roughly 70 - 75 gal, and the original ones are presumably 90 gal.
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The other thread is the one you started on March 19th, 2015 | Category: Boat Stories, Projects, Upgrades & Maintenance
I guess I should not worry so much. I was about to install a Moeller sending unit today, but it looked so flimsy I was afraid the float and thin rod would fall off and end up on the bottom of the tank. I am looking now at a VDO sending unit which has a much stronger supporting arm. Costs more, too, of course.
I never did open the tank to try to remeasure it. I think that my 'measurements' of the width were way off. I have a drawing from the owner's manual which shows the tank going across to the stove area which would make the whole width about 4 ft. With fore and aft dimension of 2 ft and a depth of 1 ft we are getting the 60 gal in the main tank. Case closed.
Want to get this done and move on to other projects...
Cheers to all with thanks.
Bob
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So some other fuel tank threads... I only went back a year or so so if you search on the words fuel tank in the forum search you will find more than 8 pages of results.
http://downeasteryachts.com/fo.....k-capacity
http://downeasteryachts.com/fo.....fuel-gauge
http://downeasteryachts.com/fo.....ank-update
http://downeasteryachts.com/fo.....ank-repair
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Thank you very much, Scott. All very interesting and informative.
I just spoke to the man who installed my new Volvo diesel engine to get his take on fuel level sending units. He recommends the WEMA type in which the float rides up and down on a tube. Very robust. They come in many sizes to fit the depth of the tank. As the consensus of the forum is that the main tank is about 12 in deep I think a 12 in sending unit would be fine for me. Then the gage would show empty when the main volume (approx. 60 gal) has been used leaving the keel section as a reserve (15 gal according to my Owner's Manual).
Wish me luck!
Bob
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I'm not sure how your getting 12 inches deep.. mine in my DE38 has to be 25inches deep at the aft centerpoint where the gauge goes in.
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Hi Scott.
What can I say? I sounded the tank with a wooden dowel at the SB edge of the sender opening and found 12" deep. On the other side it went down to 24" but moving a little bit more to port it went down to 36". Maybe not too scientific, but I did measure at least twice. So, based on Tondy's measure of 4' across and 2' fore and aft by 1' deep that gives 60 gal which is what my owner's manual says is the "main" tank with another 15 gal in "reserve". The boat is now on the hard having her bottom scrubbed and painted but when she is back in the water and I get the gage installed, I'll do some testing when I fill the tank.
I like the simplicity and robustness of the WEMA level indicator. I'll just have to suck it and see how to judge the readings in terms of actual fuel content. Having a working fuel gage will make a huge difference.
Cheers
Bob
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