PDQ OWNERS FORUM

We had the water in fuel sensor warning light flicker on the port(!) engine when accelerating to plane, but no warning light at lower rpm’s and motors ran fine. We run both Racor’s and the yanmar filter. There was no water visible in the Racor, but I replaced the sensor. We have run about 150 hours since then without any problem, but I am now again seeing the same phenomenon on the port engine. No water visible in either Racor and no issue on starboard side. Wouldn’t I see water in the Racor if there was water in the fuel? Wouldn’t both sides be affected? Wouldn’t the engine struggle? I have another sensor and they’re easy to replace, but I’m wondering if anyone else has had a similar experience. The sensor itself is no miracle piece of engineering (basically a float on a stick) and I’m wondering if it might just get “sticky” over time. It does not come on unless accelerating to plane, does not stay on and motor runs great. Any similar experiences?

I'm guessing re. the PDQ installation, but...

* The sensor is nothing more than a pair of copper stubs that allow conductivity (no float). There is little that can go wrong, other than get dirty. A wet connection can cause a false positive, as can a chafed wire. Could be a poor connection that fails at higher RPM. Could be a bad control module. But probably not the sensor (you can easily test that by disconnecting it).
* If there is only one Raycor, I'm guessing the alarm was only wired to one engine panel.
* No, an alarm will not immediately correlate to poor engine performance. Just because there is a fraction of an inch of water in the bowl does not mean the engine is getting poor or insufficient fuel.

Whether you actually need it is up to you. You can just check the bowls soon after fueling or when you check the oil.

Nick, where is that sensor located? I wasn't aware of it.

hi,

a long time ago (circa 2006 or 2007) we had the warning light go on intermittently. i spoke to pdq and they said that yanmar had problems with the filter mounted on the engine. it was mounted on a rubber grommet but still was sensitive to the amount of tightening. i decided to move the filter to the hull side. we haven't had the problem since.

i think i documented this on the forum. do an advanced search with "duetto" as author.

hi,

if you search on this topic you'll see my original question (fuel warning light). may or may not be the same thing.

I found lots of duetto posts, but not one on this particular subject. I like the answer you posted here though. I am unable to attach a photo of the sensor, but it IS a plastic post that screws into the bottom of the secondary filter. There is a plastic collar that moves up and down that post and I guess that action somehow impacts electrical impedance to set off alarm. I will check connections to the sensor next.

I am assuming this is a chronic issue related to a design problem as seems to be confirmed by duetto. In our case our primary filters are Raycors mounted on the side of the hull. The fuel then passes through the secondary filter (which has the sensor) mounted on the motor. I am relatively new to diesel engines, but assume if there was water in the fuel, it would show up in the Raycor too and it would be seen on both sides wouldn’t it?

About 3 years ago we had a bad sensor on the bottom of the Yanmar filter mounted to the port engine. It would alarm intermittently, usually at cruise speed. There was no water in the racor and no water in the Yanmar filter. I replaced the sensor and that cured the problem.

Hey Nick,
As Duetto and Alan mentioned, the on engine Yanmar fuel filter can signal water in the fuel in error. Seems a resonance at a certain rpm will trigger it. If changing revs makes it stop all is good, and you can look at replacing the float, or try adjusting the tension on the filter rubber mounts.
If changing rpm does not rectify the situation a closer look is needed.

Hope this helps
James