Water pressure gauge

[Tom S.]

Any help is appreciated, I have a 2010 Ranger Z521 powered by a 2009 Yamaha 250 HPDI series 2. My water pump gauge quit working last month. I brought it to the dealer they said the gauge was bad "so I ordered a new gauge from Ranger (still under warranty) I replaced the gauge,,,, still not working. The mechanic "guessed" it was the gauge because my engine is pissing water very strongly. My water pump is also brand new. I don't know what wires at the plug should have power and what should be ground, If I knew this I could check it with a test light.
On my engine on the top left side there is the engine temp. censor,,,, on the opposite side of the engine in the same place there is a (looks like another type of censor) with a small black hoses crimped on to the top. It is brass. Is this the water pressure censor? And if it is, "could sand clog the end of it and cause my gauge to stop working. I was gonna remove it, and check it, but I wouldn't have been able to re-crimp the hose back on.
If anyone could let me know what to check that would be great, I have been a auto mechanic my whole life so I am familiar with the way things work.
Thanks in advance
Tom S.

[mullamaster]

I would be checking the poppit valve. Have you been fishing shallow?
See this link. http://www.bbcboards.net/zerothread?id=185398

[Tom S.]

Matt, thanks for trying to help. I got up early this morning and checked the poppit valve, it was clean. I was hopeing it was gonna be dirty so my problem would be solved, no such luck. I also inspected the wires to the gauge, none of the butt connectors have come apart. So I am back to my original question, "what censor gives the gauge it's reading ?

[Charles Prestridge]

I think all the water pressure gauges utilize a pressure diaphram (no electronics). The wires that you see going to the pressure gauge is to power the light inside the gauge.

The fitting on your head (brass with black hose) is for the water pressure gauge. The hose can become clogged with debris.

Unhook the black hose from the gauge (pull it off the nipple) and unhook the hose from the motor (pull it off the nipple). You can blow thru the hose with your mouth or a compressed air line.

If you are very careful, you can hook the hose back up to the gauge. Use compressed air at low pressure to blow into the hose at the motor end. You should see the needle of the gauge move. BE VERY CAREFUL. If you put too much pressure on the gauge, you will damage the gauge and it will no longer work. You only want to put 10 - 15 psi of air pressure to test the gauge.

Good luck.

[mullamaster]

Every time I have had my poppit apart It has appeared clean, but next time on the water I will have my WP back. It only takes one grain of sand to hold it open.

Wedawee is right, you will most likely have a analogue gauge that has a annealed copper bar inside that under pressure straightens out. Like he suggested with a little air check the line is clear and check the gauge for operation. If you have a compressor at home turn the reg down

[Tom S.]

Thanks for your help guys, "but there is no hose going to the gauge, it's just a plug with four wires coming out of it. Thats what is confusing, the hose comes off the censor follows the wiring harness into the boat and doesn't go to the gauge. The hose comes into the boat then goes into the floor which I can't follow. For a sixty thousand dollar boat that is only a year old I shouldn't even have these problems. The Ranger dealer is three hours from my house, and being a mechanic thats why I am trying to fix this myself. After taking it to a Yamaha dealer and I was told it was the gauge (when it wasn't) I trust my own mechanic skills now more.

It doesn't make cense that the hose doesn't go to the gauge, "BUT it did work up until last month.

Matt, I will hook up the garden hose to the engine tonight and see if my pressure is back.
Thanks again!

[Charles Prestridge]

If the gauge is electronic, then there must be some kind of transducer somewhere to convert the water pressure to an electrical output. I have not seen that type of gauge on a boat. You would think the transducer would be somewhere under the dash or in the bilge area.

Maybe you can post in the ranger forum and see if someone can help there.

Good luck.

[Tom S.]

Charles thanks for your help, I just lifted the access panel to the bilge area, "the hose from the water pressure censor goes to a transducer mounted down there. What I am gonna do is, tomorrow (it's too dark right now) I am gonna run a new hose straight from the censor to the transducer before I run it threw the harness and start the engine. I am also gonna remove the censor in the head and check it for sand. I am sure after I remove the censor, if I see sand then there is a plug from either it or the hose.
I am getting closer to the problem ,,
I appreciate the help, sincerely
Tom

[Charles Prestridge]

Good luck in changing out the transducer. It should not be too hard. I know the normal analog gauges will freeze (if water is left in the line and the temp drops too far below freezing). I am not familiar with your particular transducer, but it would have to be similar. If you run your boat is stored where the temperature will be below freezing, make sure to unplug to hose from the pressure transducer in the bilge. This will keep it from freezing.

I hope you can get a new part without paying too much.

[Tom S.]

Problem fixed

Charles I removed the censor on the engine block, It was clean. I then removed the hose from the transducer and found that ONE very tiny piece of sand had clogged the hole in the diaphragm end. The hole in the transducer that the water passes threw to give the electric reading to the gauge is smaller then a pin (from a new shirt) "I used the very tip of a small drop shot hook to push out the grain of sand. I also blew out the hose from one end to the other to make sure there was no more sand in it.

ONE tiny, tiny piece of sand caused all this grief.
Thanks again for your help, also thanks to Matt for helping me also.