94xp fuel baffle weird question

[Minton33]

Having a weird issue with this baffle. From about halfway to full it works perfectly. Under that it’s just infinite resistance and shows empty. I cut the side out and if I test the sensors when the float is by them they work fine all the way down. I did notice that from one sensor to the next they all have continuity with each other until a little over halfway down and then none of them have continuity with each other.

The magnet on the float is in pretty rough shape and am ordering another one. Not sure if that would make any difference as like I said from half up it works perfectly. The only floats i can find look totally different but I guess they’ll work?

 

[Minton33]

No one?

 

[artr]

I have never seen a schematic of the circuit board inside of the fuel baffle so this is only a guess as to what has failed. Since you cut the side out for testing you should look for or test with an ohmmeter for a break in the trace that connects all the sensors together. That break is an open circuit that is the the infinite resistance that gets added into the measured resistors above it. It can be repaired by cleaning the broken trace by lightly sanding to remove any coating and bridging over the break with solder or a wire if the break is wide.

 

[Minton33]

I have never seen a schematic of the circuit board inside of the fuel baffle so this is only a guess as to what has failed. Since you cut the side out for testing you should look for or test with an ohmmeter for a break in the trace that connects all the sensors together. That break is an open circuit that is the the infinite resistance that gets added into the measured resistors above it. It can be repaired by cleaning the broken trace by lightly sanding to remove any coating and bridging over the break with solder or a wire if the break is wide.

Thank you for the response. I had the same thoughts. But it seems that from that point down there is infinite resistance in between every sensor. I thought about as you said bridging them all together but I wasn’t sure if it was supposed to be that way since they’re all like that from about halfway down. I just find it unlikely that there’s a brake between all of them. But at the same time anything is possible.

 

[artr]

I agree that there is unlikely to be a break between all of the sensors about halfway down the board. How did you measure that there was infinite resistance between the sensors halfway down? Did you measure between each adjacent pair of sensors?

I think because you have the board exposed you should measure across each individual sensor and resistor. The resistors should be about 10 ohms each. The sensors are reed switches, probably normally open and should be infinite resistance and then approximately 0 ohms when a magnet is placed over them. If that all checks out then all that is left is the circuit board traces and solder joints of the components.

It would be good to post a picture of the exposed board and a closeup of 2 adjacent resistor and sensor pairs so that a schematic can be reverse engineered

 

[Minton33]

I agree that there is unlikely to be a break between all of the sensors about halfway down the board. How did you measure that there was infinite resistance between the sensors halfway down? Did you measure between each adjacent pair of sensors?

I think because you have the board exposed you should measure across each individual sensor and resistor. The resistors should be about 10 ohms each. The sensors are reed switches, probably normally open and should be infinite resistance and then approximately 0 ohms when a magnet is placed over them. If that all checks out then all that is left is the circuit board traces and solder joints of the components.

It would be good to post a picture of the exposed board and a closeup of 2 adjacent resistor and sensor pairs so that a schematic can be reverse engineered

Okay I will get a picture today when I get home from work. As far as testing Continuity I tested from say the left side of the sensor to the left side of the sensor below it and that showed continuity till about halfway down. Same with the right side. They both stopped having continuity at the same sensor, which is coincidentally the same sensor that I stop getting a reading from at the plug. I held a magnet to them and tested on each side of the sensors and they all showed around 8 ohms apiece all the way down to the bottom according to my multimeter. They all seem to be functional.

In my mind idk how they would ever work without continuity between them. Shining a light through the board I can see the circuits in the board all the way down to where I lose continuity. From there on I see nothing in the board aside from the sensors mounted on it.

I tested the old one from my 96xp which is slightly different, and they have continuity all the way down to the last few inches which was destroyed by corrosion and actually had a few of the sensors fall completely off making it untestable. Shining a light through it I can see where there was a circuit between sensors all the way to the the last couple sensors where the corrosion was terrible and it became pretty hard to tell what was going on

 

[artr]

Shining a light through the board I can see the circuits in the board all the way down to where I lose continuity. From there on I see nothing in the board aside from the sensors mounted on it

So below halfway down the board there are no traces (connections between sensors and resistors) and no resistors. Just the sensors are left. If that's the case you could fix things with jumper wires soldered to replace missing traces and resistors but I don't think that would be robust enough for being submerged in gasoline and being bounced around on a jetski. You would be better off buying a used working fuel baffle.

 

[Minton33]

So below halfway down the board there are no traces (connections between sensors and resistors) and no resistors. Just the sensors are left. If that's the case you could fix things with jumper wires soldered to replace missing traces and resistors but I don't think that would be robust enough for being submerged in gasoline and being bounced around on a jetski. You would be better off buying a used working fuel baffle.

sorry there are still resistors and sensors. Unfortunately I didn’t get a chance to get pictures today. It doesn’t appear there ever was any connection between them. With light behind them I can see where it just cleanly stops. I really don’t understand how this could have been the case though. I’m thinking of just completely stripping a wire and soldering it down through the sensors to give them all continuity again.

 

[artr]

You will have a better chance of repairing it if all the resistors and sensors are mounted in the positions below. You will need to replicate all the connections for each sensor/resistor pair to match the ones above. They are probably all identical. If the resistors and sensors are through hole parts (have wires that solder into a hole in the board that goes through to the other side) it will make your job easier. If parts are surface mount they can fall off when you solder to them. There are probably traces on both sides of the board that need to be replicated because they need to cross over an existing connection. All your wires will need to lie very flat on the board so the float can side freely up and down over them.

 

[Minton33]

You will have a better chance of repairing it if all the resistors and sensors are mounted in the positions below. You will need to replicate all the connections for each sensor/resistor pair to match the ones above. They are probably all identical. If the resistors and sensors are through hole parts (have wires that solder into a hole in the board that goes through to the other side) it will make your job easier. If parts are surface mount they can fall off when you solder to them. There are probably traces on both sides of the board that need to be replicated because they need to cross over an existing connection. All your wires will need to lie very flat on the board so the float can side freely up and down over them.

Thank you much for your help. You definately have more knowledge than me on circuit boards. They do not appear to be through holes to me. I had not thought about them falling off being as they are surface mount. But I supposed if it doesn’t work anyway I can’t make it any worse. Best I can remember it at least appeared that everything is located on the same side of the circuit board on this one, which is actually the side away from the float so I won’t have to worry about that. The connections between sensors appear to be like 1/4 wide strips of possibly copper? As opposed to the very thin lines of circuits I’ve seen on most circuit boards I’ve seen.

Now the one on my 96 challenger is totally different and it has circuits zig zagging on both sides and through the board. Interestingly on it, it had a spot at the top (not the fuse) where it opened circuit. I just Soldered across it and all was well. Kinda full is halfway on the gauge and I’ve never had it empty but around empty on the gauge it’ll take 20+ gallons to fill so I assume it’s about right

If you’re curious I will try to get a picture for you this weekend. I’ve been busy trying to get the engine for my rxp back together the last couple days. Was hoping to have it running this weekend but seeming unlikely as I still have to put the head on and dress the engine, figure out how to rebuild supercharger and reinstall everything. And be a groomsman on Saturday.

 

[artr]

If everything is on one side it will be easier because gravity or a small weight will hold components while you solder. Since the fuse current is 25mA you don't need very big wires. Probably the diameter of a small paper clip so they hold there shape and stay close to the board. I would be interested in a picture or hand drawn schematic of how things are connected. Good luck this weekend.