So up to this point we have disassembled and reassembled the top end of this MerCruiser 5.7 MPI engine. We were trying to determine the cause of gallons of water in the oil of the motor. Additionally, we unable to concretely determine the source of the water ingestion. I much suspect it was a combination of multiple issues from not using the correct head gasket, not using the proper sealant on the head bolts, a bad port exhaust flapper, and the hard-wired open-through hull exhaust. Keep in mind, any one of these things can cause an issue over time. Now the question are we ready for The MerCruisers First Start?

Firstly, I’ve been anticipating that this might just not be that easy as putting everything back together and it runs. The most difficult to start was my Polaris RZR. Additionally, this boat actually started, so if it doesn’t I will have to figure out why. So with a flip of a switch, we will know the answer shortly.

The MerCruisers First Start?

So I turn on the Perco and the switch on the power up the boat. The dash the gauges light up and show that everything except the trim sender is working. So now is the moment of truth. Will The MerCruisers First Start? So, I push the toggle switch up and it cranks but does not start. I try a few more times but no luck. So we are now going to have to go to the ECM 555 manual and find the section where it says cranks but no start. Below is a link to one of the two ECM diagnostic manuals I found

There is a list of things here, but the first item say power on and listen for the fuel pump. I really don’t remember hearing a fuel pump, but how loud could it be.

It does not start! Damn!

So dejected and disappointed, I start the troubleshooting process. I connect a fuel pressure gauge to the Schrader valve and flip the ignition switch on. Additionally, according to the manual, there is supposed to be like forty PSI, I have none. It says look at the Fuel Pump Relay. It will not throw a code. So with a couple of hours of poking around and probing the harness and connectors, it looks like there is a power problem. I do not have positive voltages where I should have them and grounds where I should. The fuel pump won’t pump power up! This was my big concern about the wiring. It’s Sunday, Late, and I’m overly frustrated now!

Step Back, breath and think!

So now a couple of days later and a new scan tool on order, that will be here Thursday or Friday. Additionally, I’ve had a Dickens of a time finding the ECM 555 manual that has the sixteen Pin Connector. I will have to deal with the ten Pin connector. Poking around at the back of the boat a find a loose ground. I alligator clip it to a ground wire on the trim pump.

So will it start now?

So with the ground wire now connected, let see if it will start. With the flip of the switch, to on. I hear the fuel pump energize. It’s loud and very noticeable. I also now see the fuel pressure with pressure! About forty PSI. And now for the moment of truth. It cranks and starts! I run it only for a few seconds! We have a successful rebuild! No lifter sounds no backfire, just a loud but smooth idle! Guess I got the timing and valve lash right. Lastly, on to tidying the wiring up! Now the fun starts. The Electrical gremlins will rear their head!