Ayuh,...... Welcome Aboard,....... Yer electric fuel pump is powered 2 different ways,......
When crankin' the motor over on the starter, the outside tiny terminal on the starter powers it,.....
Once started, it's powered by the ignition circuit, through an oil pressure switch, then to the fuel pump,.....
My guess is, the oil pressure switch puked,.....
That explains why it starts, 'n runs a few seconds,.... it runs til the carb's float bowl is emptied from the fuel the starter circuit pumped into it,....
You nailed it. I spent a good part of a day going through both the fuel components and electrical systems.
Just as I was getting ready to call it a day I looked down below the port side manifold and there it was. A broken wire connection to the oil pressure sensor. I am including a couple of photos.
It just so happens that I thought the problem might be on the electrical side of the equation. And a big thank you goes out to this forum because I read every prior thread I could find that related to my problem. More than once I saw mention of the oil pressure sensor, not the oil pressure sending unit, being a source of the problem. I just didn't know what it looked like or where it was it located on the motor.
Long story short, Amazon had the sensor unit for 20.00. I went ahead and ordered one.
The unit actually arrived a day early. But it was Sunday evening the marina is about 30 miles from my home so I wasn't able to get back to the boat.
One of the reasons I didn't recognize the sensor unit is I wasn't expecting to find a dual application set up that exists for my carb 5.0 2002 mercruiser alpha one gen 2. That and the fact the replacement sensor doesn't look anything like the original.
In the photo you will see the three way connector that holds both the oil pressure sensor and the sending unit.
BTW. I also have probably about a thousand boat parts from boats I've owned over the years. My wife is always trying get me to dispose of them. Bur hey. Last night made up for all of the complaints. You will see that I was able to dig out and oil pressure sending unit I held on to for a few years!
So, being 99% certain that this is the source of my problem I have one issue left. The piece that connects both the pressure sensor and the sending unit broke in half when I was removing it from the block. Alot of rust and corrosion involved. I'm not sure that this part is mercruiser specific? It looks like the threads from the sensor and sending unit are 1/8". The thread to the block is maybe 3/8". Does anyone know if their is a mercruiser part # for this? I do have the serial number for my motor. Of course it's sitting in a notebook on my boat. I do know it starts with the 0M0 serial number. Not much help I know. I found what I think is a comparable unit on Amazon. Just not sure of thread sizes.
