My FP mini 12 has very low hours. Having said that, I always try to run it for 10-15 minutes whenever I’m on board, because “what rests..rusts”
Last season I started to experience random shut downs, with the error message “Oil sensor switch shut down”, or something like that.
The FP 12 has 2 oil sensors..
One is a simple switch with NC contacts, and the other is a VDO oil pressure sensor.
It was the opinion of FP service that the contacts on the switch had degraded over time, and that this should be replaced.
Being proactive, I thought I’d change the VDO pressure sensor at the same time.
I ordered both parts from FP, and they promptly shipped them
On the 49, the genset is sub-floor, and access is quite challenging for any type of moderately difficult service
The 2 sensors were in the most difficult place to access; that being at the bottom of the genset under the oil filter.
So… drained the oil from the engine, and pulled the filter.
The VDO pressure sensor was above the oil switch, so that had to be removed first.
To say that it was in tight is an understatement. It just wouldn’t budge, and forcing it wasn’t a great idea,
So, made a custom tool which was essentially a longer wrench with an offset in it to get at the sensor flats more easily.
And with less than moderate pressure, the damned thing snapped off, leaving most of the threads buried.
I certainly know how to remove stuff without breaking it. I just couldn’t figure out how this “5 minute job@ turned into a nightmare.
Well, on inspecting the original VDO sensor, the threaded shaft was aluminum instead of what the newer sensor had (steel shaft with cadmium plating)
But, the reason this became a nightmare was that FP installed the sensor with some variation of JB Weld.
I inspected the snapped off sensor under magnification, and the left over “sealant” was as hard as a rock.
As mentioned, access to this area was extremely restricted. I had thought of possibly getting an easy-out into there, and getting the busted off stud out.
But… absolutely no way. On the oil pressure sensors, there is a very tiny hole in the mounting stud which controls oil pressure into the sensor.,
So, there was just a pinhole visible, and absolutely no way of getting a tool into it.
I really started to think this was going to mandate pulling the genset, which was a horrific thought.
Upon inspection, I noticed that the oil pressure sensor and switch were not screwed into the engine block, but actually mounted on a brass manifold, which was affixed to the block with 2 long M6 bolts
There was a hose with a 90 degree fitting at the end of the manifold that fed oil to both sensors .
I changed my underwear, and got to work with removing the manifold.
With that in hand, took the assembly into the shop to firstly remove the other sensor.
No way it was going to move. More JB Weld, (or whatever it was) holding very firm.
Got out a heat gun, and with a very patient effort, I was able to remove the second sensor without snapping the threaded shaft.
It was now time to figure out how to remove the busted aluminum shaft that was firmly embedded into the manifold
With great care, a lot of patience, and prior machine shop experience , I was able to drill out the aluminum stud and re-tap the hole which was 1/8” NPT.
I was now back to “square one”, which felt a lot better than pulling the genset.
Installed the manifold back on the engine, and carefully wound in the 2 new sensors.
Fired it up, and it all ran.
This was a “15 minute job” that ended up taking almost 6 hours.
So,,, here is my advice.
If you need to change either the oil pressure switch or pressure sensor, do not attempt to do so with the sensors mounted on the engine.
Remove the brass manifold block, and take it to workshop vise. This is a guaranteed way to do this work without the risk of snapping off the sensor.
To reiterate, there was no way this was due to over torquing the sensor when removing it. I’m relaying this info so that other folks don’t have the horrific moment of snapping off the sensor, and visualizing their cruising plans crashing to the ground.
Last season I started to experience random shut downs, with the error message “Oil sensor switch shut down”, or something like that.
The FP 12 has 2 oil sensors..
One is a simple switch with NC contacts, and the other is a VDO oil pressure sensor.
It was the opinion of FP service that the contacts on the switch had degraded over time, and that this should be replaced.
Being proactive, I thought I’d change the VDO pressure sensor at the same time.
I ordered both parts from FP, and they promptly shipped them
On the 49, the genset is sub-floor, and access is quite challenging for any type of moderately difficult service
The 2 sensors were in the most difficult place to access; that being at the bottom of the genset under the oil filter.
So… drained the oil from the engine, and pulled the filter.
The VDO pressure sensor was above the oil switch, so that had to be removed first.
To say that it was in tight is an understatement. It just wouldn’t budge, and forcing it wasn’t a great idea,
So, made a custom tool which was essentially a longer wrench with an offset in it to get at the sensor flats more easily.
And with less than moderate pressure, the damned thing snapped off, leaving most of the threads buried.
I certainly know how to remove stuff without breaking it. I just couldn’t figure out how this “5 minute job@ turned into a nightmare.
Well, on inspecting the original VDO sensor, the threaded shaft was aluminum instead of what the newer sensor had (steel shaft with cadmium plating)
But, the reason this became a nightmare was that FP installed the sensor with some variation of JB Weld.
I inspected the snapped off sensor under magnification, and the left over “sealant” was as hard as a rock.
As mentioned, access to this area was extremely restricted. I had thought of possibly getting an easy-out into there, and getting the busted off stud out.
But… absolutely no way. On the oil pressure sensors, there is a very tiny hole in the mounting stud which controls oil pressure into the sensor.,
So, there was just a pinhole visible, and absolutely no way of getting a tool into it.
I really started to think this was going to mandate pulling the genset, which was a horrific thought.
Upon inspection, I noticed that the oil pressure sensor and switch were not screwed into the engine block, but actually mounted on a brass manifold, which was affixed to the block with 2 long M6 bolts
There was a hose with a 90 degree fitting at the end of the manifold that fed oil to both sensors .
I changed my underwear, and got to work with removing the manifold.
With that in hand, took the assembly into the shop to firstly remove the other sensor.
No way it was going to move. More JB Weld, (or whatever it was) holding very firm.
Got out a heat gun, and with a very patient effort, I was able to remove the second sensor without snapping the threaded shaft.
It was now time to figure out how to remove the busted aluminum shaft that was firmly embedded into the manifold
With great care, a lot of patience, and prior machine shop experience , I was able to drill out the aluminum stud and re-tap the hole which was 1/8” NPT.
I was now back to “square one”, which felt a lot better than pulling the genset.
Installed the manifold back on the engine, and carefully wound in the 2 new sensors.
Fired it up, and it all ran.
This was a “15 minute job” that ended up taking almost 6 hours.
So,,, here is my advice.
If you need to change either the oil pressure switch or pressure sensor, do not attempt to do so with the sensors mounted on the engine.
Remove the brass manifold block, and take it to workshop vise. This is a guaranteed way to do this work without the risk of snapping off the sensor.
To reiterate, there was no way this was due to over torquing the sensor when removing it. I’m relaying this info so that other folks don’t have the horrific moment of snapping off the sensor, and visualizing their cruising plans crashing to the ground.
