Mercruiser Carb Problem

[Tahoe Q7i]

Morning all, new to forum and looking for answer for my 2009 Mercruiser 5.7 2 barrel engine. Engine starts easily, runs 15 to 20 seconds and quits. Turn key off then restarts easily. Runs 15 to 20 seconds again then quits. After starting several time, it will run fine. It seems after engine is warmed up, no problems. I'm thinks it's the TKS carb. Any thougths?

 

[Rick Stephens]

Could also be the oil pressure switch that powers the fuel pump. When you crank the engine the starter motor powers the pump as a primer. As oil pressure builds the oil pressure switch connects the power to the pump as long as pressure is there. Switches wear out. Easy to test.

Welcome to the forum!

Rick

 

[AShipShow]

What Rick said!

Theres should be an oil pressure switch on the port side near the oil filter, its one with 2 wires... Try hooking up a multimeter in continuity check and start the engine, after a second or 2 it should close the switch...If its not, replace the switch (assuming you have already verified you actually have oil pressure).

 

[Tahoe Q7i]

Thanks Guys, I will check the switch. I do have good oil pressure.

 

[crazy charlie]

I had very similar.pull the carb filter and see what it looks like.mine had a clog with something that looked like "dippity do" . Creamy opague crap.have a look.charlie

 

[Tahoe Q7i]

Thanks Rick Stephens and Mad Props for helping me with the oil pressure switch. Put new one in and boat cranked fine and spent a nice day on the water. This morning we were going to take it out and I tried to crank before leaving just to make sure everything was still ok. Boat won't crank at all.Now my fuel electric fuel pump is not working at all. I took fuel line loose at carb and tried to crank and had no fuel pressure at all. I can spray gas into the carb and it will run as long as I keep pumping it. Is there a fuse or relay for the electric fuel pump.

 

[Rick Stephens]

There is not a fuse unless there is a relay. I wired my pump in with a relay to provide power to the pump, the relay is switch by either the oil pressure switch or the starter.

Normal wiring is the purple wire from the ignition switch goes to the electric choke, then from there to the oil pressure switch. Use a test light and see if you have power.

Also, on the starter solenoid itself, the small lug facing outboard between the two big lugs is the one that powers the fuel pump when the starter is running. I will short that lug to the solenoid top lug to prime my carburetor before starting the first time each season. You can check it with a test light as well. It is shown as purple/yellow in the diagram. Note, diagram is also 'marked up' by achris to show how to add a solenoid.