Cruised for 15 minutes. Then Towed back.

[milkyway]

Mercruiser 5.0 Alpha 1999 8 cyls.<br /><br />I took the boat out first time this season last weekend. Cruised for 15 minutes, I stopped to anchor, then motor died. Restarted, then quickly died - happened about 3 times. Motor started strong when in full wot but motor died within seconds. Attempt to restart more than 8 times was not successful. Engine cranked but did not start. Had to be towed.<br /><br />At home, I replaced the fuel/water separator, did not observe any water (transferred fuel to a clean bottle and watched for water), changed plugs, changed plug wires. Two plugs smelled gas, and all 8 are black ( from oil fogging?) Recharged battery. Tried to start, got strong cranking, motor started on 4th attempt, then died after 20 seconds. Tried restarting 4 - 5 times, good/strong cranking, but did not start again. Electric fuel pump is working.<br /><br />Tomorrow,I will check the fuel filter on the carburetor inlet and check for blockage.<br /><br />Can someone give me a few other leads? <br /><br />Thanks.

 

[Gary H NC]

Re: Cruised for 15 minutes. Then Towed back.

sounds like maybe a carb related problem..<br />That would be my first thoughts..<br />Black fouled plugs sounds like the carb is loading up.

 

[Don S]

Re: Cruised for 15 minutes. Then Towed back.

Sounds more like your oil pressure switch (Not the gauge sender) went bad. It's what supplies power to the electic fuel pump after the starter stops cranking.<br />Look at the drawing below. Item 5 is the switch.<br />It could also be corroded connectors for the wires or a wire fell off. It's just above the oil filter block location on the port side rear of the engine.<br /><br />A quick test would be to hook the 2 wires (that go to the oil pressure switch) together. Start the engine and see if it keeps running.<br /><br />

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

Carburetor? Ouch. I know nothing about this carb.<br /><br />Don, I had this problem last year when I knocked one of the wires on the oil pressure switch. You led me to this solution and everything went ok last year. Then, I replaced the oil press switch in summer 2005 'coz it was really badly corroded. No problem entire season. I double checked the connectors yesterday and they seem tight. <br /><br />Tomorrow, I will hook the 2 wires and start the engine. I hope you're right. My wallet gets nervous everytime something is wrong with my boat. <br /><br />I will post my results tomorrow.<br /><br />Thanks to both of you.

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

Just a follow up regarding the electric fuel pump which is related to the prognosis - sometimes I can hear the pump hissssing just before hitting the ignition, and sometimes I don't. Why is that?

 

[Don S]

Re: Cruised for 15 minutes. Then Towed back.

You shouldn't hear anything from that pump till the starter solenoid engages. If you do, there is something else wrong. Are you sure it's the pump?

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

Don - The pump is my best guess. The sound is like humming or hissing. It's like being energized. I heard this sound when I first turned the key but before hitting the ignition, after I have replaced the fuel filter and the filter was only half full. I waited to hear this sound after the first attempt but it did not come back. I heard this familiar sound also last year. I just couldnt be positive if it's everytime I replaced the fuel filter. I will check again tomorrow.

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

Here's the result of my work today.<br /><br />I disconnected the 2 wires that come from the harness and connect to the switch, and then connected these wires directly. The engine started right away and ran for about 15 seconds then died. It again ran twice for about 10 - 15 seconds and then died again. So it must be something other than the oil pressure switch.<br /><br />I disconnected the fuel line ( that line that comes from the electric fuel pump )that is connected to the carburetor and expected to get some spill of gas and also to see the fuel filter. No gas spill and no filter. I thought I read the schematics correctly - finding a small filter, that might be clogged. <br /><br />Any more suggestions ( while I am recharging the battery)? It looks like I have to spend time home this coming weekend.

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

I also did not hear again that familiar hummmming and /or hisssssing sound.

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

Anyone?

 

[Don S]

Re: Cruised for 15 minutes. Then Towed back.

Disconnect the purple wire from the oil pressure switch. Turn the ignition switch to the run position and with a volt meter, check the voltage on the purple wire. It should show close to battery voltage. If there is nothing there, you have a wiring problem.

 

[lilmandavis]

Re: Cruised for 15 minutes. Then Towed back.

how much fuel pressure is there? does it run when spraying some gas down the carb?

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

Thanks for the lead. Will do it tomorrow night.

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

Fuel pressure? I have not done any checking on this yet. How do you go about this? Assuming there is power on the purple wire that Don has advised me to check, do I disconnect the line that connects to the carb and then turn on the ignition key halfway and see if fuel will be coming out from the pump's line? At what stage does the electric fuel pump energize? I suppose that the 2 wires on the oil switch should also be hooked together directly when doing this test so that it is not necessary to run the engine, which is the main problem.

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

Here are the results.<br /><br />1. The purple wire has 12.5 volts.<br />2. I jumped the purple and the purple/yellow and turned the ignition key to ON. The electric pump ran.<br />3. I re-connected these 2 wires to the oil pressure switch. Turned the ignition key to ON - the electric pump did not operate. It was totally quiet. <br />4. I jumped again the purple and purple/yellow adn turn the key to ON. The electric pump turned on. <br />5. While the electric pump was running, I looked at the throat of the 2-barrel carburetor and there was no fuel coming in. There was no activity. First time to do this, but believe me nothing was happening inside the carb.<br /><br />Is the oil pressure switch shot? Is the electric pump also shot? Coincidence? <br /><br />Because of rain showers, I did not have time to disconnect the fuel line from the carb and run the pump to see if fuel will spill out and how much.

 

[bruceb58]

Re: Cruised for 15 minutes. Then Towed back.

Did you happen to try and start your engine during test #5?<br /><br />When it starts, which I think it will, pay close attention to your oil pressure guage

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

I did not crank the engine on test #5. I have done this many times and it just kept dying. I was just on the RUN position of the key ignition.

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

I think the switch gets power initially when you crank the starter. So since I did not START the ignition key, the switch therefore did not receive power and then to power up the electric fuel pump. So the switch must be OK. I<br /><br />It has to be the fuel pump.

 

[milkyway]

Re: Cruised for 15 minutes. Then Towed back.

It will cost me another $250 to replace the electric fuel pump.<br /><br />Since I cannot perform a pressure test coz the engine won't start, what's the alternative testing can I do to conclude that this pump has called it quits?

 

[Don S]

Re: Cruised for 15 minutes. Then Towed back.

When you hook the purple and the purple/yellow wire together and the pump runs, start the engine. If you could see fuel coming out of the carb with the engine not running, there would be something wrong.<br /><br />

I think the switch gets power initially when you crank the starter. So since I did not START the ignition key, the switch therefore did not receive power and then to power up the electric fuel pump. So the switch must be OK.

That's not how it works. <br />The fuel pump gets power from the starter solenoid when cranking (comes from the outside small terminal on the starter, see diagram).<br />Then when it starts and the oil pressure builds, it pressureizes the switch which closes and lets the power through to the pump. It's run that way to keep the pump from running when the engine is not running.