I thought that one was aft of the gauge sender off the tee piece. This mystery one is forward of the gauge sender and directly into the block.
I'll get one next time I'm working over my his mooring. Also, with the oil pressure switch for the ECU/fuel pump, should that trigger an alarm if disconnected?
Can't tell the colour. It's got an old black dirty sheath over the actual cable. It's a single wire bolted to the top. It's not in the manifold, it's in the block next to where the 2 oil pressure senders are. The pressure sender with a single wire and the "I presume" oil switch which has a 3 pin plug.
Sounds like a knock sensor
knock sensor has a single blue wire and a unique connector, the knock sensor is typically screwed into a Y fitting at the block water drain,
No, it's not on the drain plug but it does appear to be screwed directly into the block, it's tight against the oil pressure sender, so tight in fact you can't remove the single wire plug that slides onto the sender. he's my photo realist rendering, I'll take a pic next time I'm passing the boat.
i think it very well might. As for the oil pressure switch, if that was disconnected should that trigger an immediate alarm if the engine is running.
No, there is a crystal inside that generates a specific frequency with engine running. If frequency changes due to a knock the signal is received by the ECM which changes timing to eliminate knock
Ah, no. I meant the oil pressure switch, the 3 pin one next to the oil pressure sender for the gauge. If that's disconnected should that trigger an alarm or is it normally open and would have to be shorted to trigger it?
Yes, the 3 wire sender should be a code with it disconnected, but it doesn't go to the gauge it goes to the ECM. The gauge sender has a single Dark Blue wire on it
yeah, it was the gauge wire that lead me down this path. Owner had a fluctuating gauge, turns out the plug had come loose and the only thing keeping it on was the fact it was trapped by the knock sensor. Was unable to remove it as it's totally trapped by it, anyway, once fully seated gauge is fine. I did unplug the 3 pin switch to see if it would trigger the alarm and stop the fuel pump but nothing happened, is there some built in delay on the ECU?
ah ok, so if I probe the sense wire i should see that state change from ignition on/engine off to engine on?
Should but I've not done that, probably see something like 0V to 0.5V. I have watched the voltage change from key ON to Run
I'll give it a probe next time i'm out. Owner is just a little paranoid after we found the warning buzzer had been removed by a previous owner and then the fluctuating gauge on his weekend away. We get the test alarm when switching the ignition on and the gauge is fine now but would be nice to let him know the ECU sender is ok too.
