PDA

View Full Version : Fuel Sending Unit Repair


Skipper
11-12-2010, 05:25 PM
Late in the season, the fuel sending unit went out on my '95 Prostar. Somebody suggested that it could be fixed. Instead of fixing it, I purchased a new one for $160.00 plus shipping. I left the old one on my work bench....until today.

If you have this type of fuel sending unit, and it is inoperative, it is likely that the magnets have come dislodged from the foam float. It is a simple repair to get you back on the water.
62883

There are three main components: The tube assembly, the circuit board, and the float. To disassemble the unit, remove the two screws at the bottom of the tube and remove the plastic cap. Then unscrew the two nuts at the top of the unit to allow the circuit board to slide out of the tube.

The culprit in my unit were the two magnets that are supposed to be lodged in the foam float. They came out of the float and were resting on the tab at the bottom of the circuit board. I just used some 5 minute epoxy to connect the magnets back into the float. Then I used a fine file to smooth out the repair.
62884

I tested the unit by attaching an ohm meter to the circuit board, then moving the float. You can see in the next pictures that the reading on the guage changes as the float goes from the top (full) toward the bottom (empty).
62885
62886

Reassembly is just the reverse of disassembly. I cleaned everything up with WD-40 first. Just be sure to insert the foam float into the tube before pushing the circuit board all the way to the top or the tab at the bottom of the circuit board will prevent you from inserting the float. Once assembled, I tested the unit again, this time by holding it right side up and upside down. This just verified that the unit is back in action. You can also connect it to the fuel guage wires and (with the key on) turn it up and down to view the fuel guage changing.
62887


Hope this helps somebody else in the future. I sure could have used that $160 some place else. This repair took only about 20 minutes and cost nothing. ;)

FrankSchwab
11-12-2010, 05:41 PM
Thanks, Skipper, that's the best write-up I've seen on this.

I had to do the same to my boat 4 or 5 years ago; at that time, there were a few active threads on here about re-attaching the magnets. Haven't seen another mention since then.

/frank

wtrskr
11-12-2010, 11:26 PM
When I first purchased my 1994 prostar 190 this summer I attempted fixing mine. I reattached a magnet that was loose without any improvements. I think my problem is that the foam float gets stuck.

I may give mine another try next year after seeing that you were able to successfully fix yours.

FrankSchwab
11-13-2010, 01:15 AM
I found the same as Skipper - I had to do some shaving of the float to get it to move smoothly without sticking.

Skipper
11-13-2010, 09:37 AM
There are two magnets. One goes on each end of the foam in the slot. If you have only one magnet, then it will not trigger the sensors in the circuit board. Using a fine file, I removed all of the epoxy covering the magnets on the foam and made the overall surface smoother.

Skipper
11-13-2010, 10:16 AM
When I first purchased my 1994 prostar 190 this summer I attempted fixing mine. I reattached a magnet that was loose without any improvements. I think my problem is that the foam float gets stuck.

I may give mine another try next year after seeing that you were able to successfully fix yours.

The tube in my unit had some old fuel residue built up inside. I cleaned the tube and the circuit board with WD40. You can test the system by connecting to an ohm meter and moving the foam float across the back of the circuit board. The reading should change with the position of the float. If this works, then after you reassemble the unit turn it up and down and the foam float should fall freely. If it is cleaned up inside there should be nothing for it to hang up on in the tube. Also, be sure to file or sand down the front of the float where the magnets are closest to the circuit board. This will keep that surface smooth and will give the best interaction between the magnets and the circuit board.

east tx skier
11-13-2010, 10:47 AM
Excellent walkthrough. I added it to the FAQ.

WTRSK1R
12-09-2010, 07:15 AM
When I first purchased my 1994 prostar 190 this summer I attempted fixing mine. I reattached a magnet that was loose without any improvements. I think my problem is that the foam float gets stuck.

I may give mine another try next year after seeing that you were able to successfully fix yours.

I used to have a 92 ProSport 205 and when reformulated fuel came to our area in the mid 90's I had the same issue with the foam getting stuck. I think it swelled slightly with whatever they add to the gas. Anyway, I was able to sand it down slightly all the way around the edges of the float and did not have any further issues with the float for the remainder of the time I had the boat.

Steve

JMann
12-09-2010, 01:49 PM
I bought a new sending unit on skidim for $60. Seems a lot easier to replace than repair.

Either way thanks for the write up very informative.

mbeach
12-16-2010, 09:43 PM
only trick to the repair is aligning the magnets so the poles repel each other. can test by taping magnets in place and sliding along the powered circuit board while watching the fuel gauge.

Worthing skier
01-09-2011, 07:04 AM
Hi all

My Fuel gauge reading was playing around a bit last seat season , normally reading low.
With the track record of the sender units I have today taken it out with a view to find a magnet related fault , however the sender unit I have is a plastic tube and it does appear to have any retainer screws to enable me to get in side it .
By tipping up and down I can see the float move around but it does get stuck , which I am sure the the route cause of the problem .
There is a plastic plate on the bottom of the unit , which I would thin could be prised off and re glued .
Has any one come across the type of sender unit and if so how did you get inside.

thanks


Kevin

1993 prostar 190 285 hp inamr.

Worthing skier
01-09-2011, 10:26 AM
Update ,

Pried off the lower plate , sender setup up and design same as pictures, found both magnets stuck together in the middle of the float, cleaned the tube , glued the magnets back in their correct site (poles apart) , sanded down all the faces of the float , rebuilt it . glued back on the base cover.
Tested in and out of tank , now gauge works good as new .
Cost me 3 for the glue and a couple of hrs but saved me 150.00 for the part and I now know exactly how it works and it is done correctly (priceless).

Many thanks to all for this thread.


Kevin

mrprostar
02-22-2011, 08:25 AM
Plus one more for this being the problem. Solved now. Thanks.

Just one question. My magnets were stuck together when they fell out. They are supposed to go into the slots on the top and bottom of the float and not in the middle? They need to be put in so they repel each other? I put them in the middle and the gauge was working, so I didn't think much of it until I came back and looked at the pictures again.

NatesGr8
02-22-2011, 02:21 PM
I did this same repair on my 94 Prostar about 3 years ago...worked like charm. Excellent write up!

Barefooter92
04-20-2011, 12:18 PM
Going to work on my fuel sender this weekend and dug this thread out.

What epoxy shall I use for the magnets submerged in fuel?

Worthing skier
04-20-2011, 01:14 PM
I just used super glue

captkidd
06-13-2011, 09:58 AM
Hi all

My Fuel gauge reading was playing around a bit last seat season , normally reading low.
With the track record of the sender units I have today taken it out with a view to find a magnet related fault , however the sender unit I have is a plastic tube and it does appear to have any retainer screws to enable me to get in side it .
By tipping up and down I can see the float move around but it does get stuck , which I am sure the the route cause of the problem .
There is a plastic plate on the bottom of the unit , which I would thin could be prised off and re glued .
Has any one come across the type of sender unit and if so how did you get inside.

thanks


Kevin

1993 prostar 190 285 hp inamr.

My '94 PS205 also has the plastic sending unit tube. After reading this thread I pulled the sending unit out and sure enough, the magnets were stuck to the back of the circuit board (I had to use a razor knife to cut the bottom plate off the tube). It looked like the magnets had been closer together, possibly one on the end and the other near the middle (based on where it looked like they had been glued), so this is how I reglued them. Now a few questions:

- Should the magnets be at opposite ends of the float, with the poles repelling each other?

- Are the magnets supposed to touch the circuit board as the float slides up and down? Mine appear to be about an 1/8" from the circuit board.

- If I reassemble the unit and reconnect the wires, will the fuel gauge register full if I turn the sender upside down and let the float go to the top, or does the unit have to be submerged in fuel in order to work?

Thanks.

-

wgtruemper
07-10-2011, 09:34 PM
Awesome write up, I pulled my sender this weekend and found 1 magnet completely dislodged. Works great now, hopefully it stays that way.

formosa
07-12-2011, 12:54 AM
Great write up - thank you. I would only add that I only had one magnet on my float. I confirmed this by only finding one magnet when disassembling, as well as there was only one visible area on the float that anything was attached to. Not having another magnet handy, I tested successfully with one magnet (both ohm meter and fuel gauge). I do not want to confuse anyone off your instructions, just relaying my situation.

Also, how did you manage to get the round/slotted nuts off to remove the circuit board? I ended up using vice grips to loosen although based on the amount of work I put into it --- I'm certain there must be the right/better tool given the slots on each side of the bolt.

Thanks again - this is an awesome write-up!

jude09
07-12-2011, 06:02 PM
Did you have to remoce the tank

Skipper
07-12-2011, 07:42 PM
Did you have to remoce the tank

You must at least disconnect the straps and pull it out to clear the sending unit. Really not that big of a job. Have to first remove the combing pads in the back corners. Then the carpeted back filler board. There are just clamps that lock onto the tank. Unscrew the clamps and the only thing left holding the tank in place is the filler hose.

monsoon
07-19-2011, 07:21 PM
Just did this repair on my '98 Prostar 190 a couple weeks ago after reading this thread. After disassembling the unit, I found only a single loose magnet inside the cylinder. I figured I had dropped the other one when taking it apart. Looked around nervously on the floor for a while, then inspected the float and saw only one end of the slot showed signs of old glue where only the single magnet would have been mounted. I carefully sanded the outside radius of the float to reduce its size and allow it to move freely up and down inside the cylinder, remounted the magnet with super glue, reassembled the unit, and it's been working fine for two weeks now.

jeverett
07-19-2011, 07:43 PM
It was a heck of a lot easier just to buy a new one from Skidim.

ricford
07-19-2011, 07:59 PM
But a heck of a lot cheaper and satisfying to do it yourself. Just completed this fix using this thread two weeks ago on my 96 prostar. Worked like a charm, and I borrowed the super glue so it didn't cost me a cent. Thanks very much!!!

monsoon
07-19-2011, 07:59 PM
"Easier to buy a new one"... Maybe... I'm not knocking Skidim here, I love the place and how helpful they are, but they haven't built a very good database on what model sending unit fits what year and make MasterCraft yet. After asking me if i had a 2 or 3 wire unit, and after having to get back to them the following week (boat and lake house is an hour away from where I live) they then asked me how deep my tank was. Seems there are 3 or 4 different length units to choose from. I told them I'd have to get back to them again the following week. I took a tube of super glue with me and while i had the unit out to see how long it was, I opened it up and did the repair.

If you're going to by a new unit, you'll need to know these two things.

725mastercraft
03-31-2013, 08:17 AM
I have a 1993 PS190 and my fuel level sender did not look exactly like the one in the OP picture. In fact, the bottom of the unit was sealed with no way to disassemble it without tearing it apart. So, I ended up buying an brand new MasterCraft fuel level sending unit for 70$. The new one looks more sophisticated in the fact that it is a much narrower aluminum tube. Apparently there is no float inside the new one. Worked very well. Price for a brand new Mastercraft fuel sending unit, 70 bucks. Price for a brand new prostar190, 60 some K. Fixing a 20 year old boat myself, priceless! :)

mbeach
03-31-2013, 09:31 AM
magnets must repel each other and are placed at ends of float. easy fix as long as the polarity of the magnets is oriented correctly.

FrankSchwab
03-31-2013, 01:52 PM
After seven years, mine broke again. Rather than take it apart and fix it again, I ordered a unit from Wema (http://wemausa.3dcartstores.com/Fuel-or-Water-Level-Sensor-4--60-in_p_9.html) that seems nicer. Everything is protected inside the stainless steel tube, except the float (and presumably magnets), which have a bit more clearance on the shaft than the float on the last one did inside so should be less likely to hang up.

Worked fine so far on the one trip we've done.

Jerseydave
06-10-2013, 02:26 PM
So how is everyone's repair holding up? My '93 prostar sending unit needs repair or replacement, but I only use the boat 10-12 times a year and I want to fix it so it lasts for many years.

Just mostly wondering if the super glue (or epoxy) will last long since it's exposed to gas.

catamount
06-10-2013, 03:34 PM
I was going to attempt the repair but found my sender beyond repair. I ended up buying a brand new ISSPRO 10" unit from https://www.dieselperformanceparts.com/ for $44 + shipping.

Table Rocker
06-10-2013, 04:35 PM
I used PermaTex Threadlocker Blue on mine after reading up on how it tolerates gasoline. It is still doing well.

Tateau18
06-10-2013, 11:15 PM
Tried this repair tonight. Got a good reading on the ohm meter after repair but the gauge is still showing empty... Any ideas what it could be? Thanks for the help.

mikeg205
06-10-2013, 11:55 PM
Gauge may have given up it's ghost... here's an inexpensive replacement http://www.cheaperthandirt.net/product/5-5101960?utm_source=GoogleShopping&utm_medium=organic&gclid=CJXZ8uSN27cCFdFDMgodKhQAIQ

Skipper
06-11-2013, 07:55 AM
You can try connecting the sending unit to the wiring harness and turning it onto its side to move the float. If you are getting the proper readings when you bench test the sending unit you should see the guage move as you tilt it. If not, perhaps you don't have the wiring harness connected to the proper terminals? And of course the guage could be bad too.

JimN
06-11-2013, 08:51 AM
Tried this repair tonight. Got a good reading on the ohm meter after repair but the gauge is still showing empty... Any ideas what it could be? Thanks for the help.

Check for voltage at the pink wire to the sender. It's not high current, so there's no danger of sparks. Touch the pink wire to the black wire at the sender. If you see no movement, do the same at the gauge and see if it pegs the needle. If it pegs the needle at the gauge, you have a problem with the wires or a terminal.

Cosmo
06-22-2013, 04:24 PM
I just wanted to comment on this thread as a new(new to me, I just bought a 92 prostar 205) mastercraft owner. I read this randomly while surfing the net, and thought I would give it a shot. While it took me longer than 20 minutes, this seams to have fixed my sending unit. My fuel gauge is now working again. Mark me down as another person who this fix has worked for. Thanks for the thread!