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Another old boat gas gauge issue


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Baggerlance

I'm sorry to resurrect another gas gauge topic but scrubbed the threads and didn't see the additional info I'm about to post.

My 1999 VLX needed a new fuel sensor because the gauge stopped working. I pulled the old sensor and once out of the tank I was able to move the lever and see the gauge move up and down. So I knew the wiring and gauge were OK. Given the reputation of old sensors I figured it was time to replace it, but not sure exactly why it wasn't moving up and down with the gas level in the tank.

Never the less, newer is better so in went down to my local big box marine store and picked up a generic float sensor nearly identical to the one I pulled, followed the package instructions and put it in a tank full of gas. After install it immediately started registering a nearly full tank! Yay problem solved, until I started smelling gas fumes.

I opened the rear seat area and noticed gas leaking at a decent rate from the new sensor. While on the water I tightened down several of the five screws that seemed a little loose, but not "lock down tight". It slowed the gas leak but not enough to stop a small leak. Blower going I headed home. 

It was a quandary as to why the leak was occurring, so I pulled the sensor, checked the alignment of the float arm and determined that it may not have been seated well. So I adjusted the arm seating and made sure it could still move up and down without being blocked by anything in the tank (11:00 for anyone with a 99 VLX)) and reinstalled the sensor. Long story short it still leaked ever so slightly. I ordered a new gasket set from the manufacturer and reinstalled. During the process I learned there are two types of threads that ship with these - course and fine. I looked at my original screws and compared them with the default big box sensor screws. The original screws were course and the ones I installed were fine. I can only assume I stripped the threads installing the sensor and that was the cause of the leak.

Now that I "screwed up" pardon the pun, I went ahead and installed the new gasket kit with fine threaded screws wrapped in plumbers tape. Probably another bad idea but it seemed to stop the leak.

Now for the second weird issue that is not on this forum.

After reinstalling the Medallion gas gauge will not reset back to zero. At power-on the gauge needle starts clicking its way up to the correct position, then when powered off it stays in that position. At the next power on the needle continues to buzz and click its way up to another higher fill level as though its previous position was at zero. It continues in this manner for each reset until the needle has nearly made a 360 degree turn without ever returning to true zero.

Strange. This seems to be a ground issue and clearly electrical but weird gauge behavior I've not found the solution for. My next step is to do a reset of the gauge MDC with the kill switch, then unhook the batteries and reset, then trace grounds.

I've you've read this far thanks and any suggestions welcome. If interested I'll post a photo of the gas gauge needle pointing at 5:00 when full is 10:00.

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If the gas leak comes back you can pick up some gas resistant sealant (I used Seal All brand) to put around the gasket and screws. I had the same thing happen when I replaced my sender. In my case the tank had become slightly warped where the sender flange mounts which didn't allow a complete seal from the gasket.

Regarding the fuel gauge - if the needle doesn't reset and behaves erratically like you describe, that nearly 100% of the time indicates a bad gauge. You can rule out any wiring issues by disconnecting the 18 pin connector on the MDC and checking the resistance between the pink wire and black wire. You should get between 33 and 240 Ohms (full to empty). More details on the troubleshooting guide here: https://cdn.bakesonline.com/media/resourcelibrary/MedallionII_Troubleshoot.pdf

If you get the correct resistance reading then your gauge is the culprit. You can switch connectors with another gauge just to be sure there's not a wiring harness issue from the box to the gauge but that's pretty rare.

I've had to replace nearly all of my gauges and they all seem to behave similar to this on their way out. You might key it on one day and it will be back to normal...then next week it goes haywire again.

 

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Baggerlance
7 hours ago, drh said:

You might key it on one day and it will be back to normal...then next week it goes haywire again.

 

Yep. That's what it's doing. Thanks for confirming. I'm going to try and go direct to Medallion and see if I have any luck buying direct. I know Bakes has some original cluster gauge units in stock. I'm not ready to go with Faria just yet.

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3 hours ago, Baggerlance said:

Yep. That's what it's doing. Thanks for confirming. I'm going to try and go direct to Medallion and see if I have any luck buying direct. I know Bakes has some original cluster gauge units in stock. I'm not ready to go with Faria just yet.

It is entirely possible that you have a bad solder joint inside the Medallion unit.  You can remove it and resolder everything.  It has helped others in the past.  Cheap to do, and entertaining for the first few minutes.  Bear with it and do everything, though.

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Baggerlance

Thanks @justgary I may give that a go. I have seen threads where folks have dug in and resoldered the connections with some success. Soldered connections age of course, and Texas weather extremes does take its toll.

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