Mercury 150 optimax No power to ignition coils or fuel pump

Matt musky

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Apr 4, 2017
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#8
April 13th, 2017, 06:12 PM
Hi
After winter storage I can't start my 2006 mercury opti 150. I checked the key switch and kill switch. I have power on the purple wire at the motor . I've tried switching the relays out from the trim still nothing.
I have no power to the coil of the master power relay . If I jump the relay I can get power to the fuses and the fuel pump. I have one side of the coil with 12v to ground ( I put one lead of tester on battery ground and the other in the coil side of the relay harness)but I have nothing if I stick both test leads into the coil with key on. So something is preventing the coil from getting a negitive to close the relay and start the motor any thoughts ? Could it be a sensor in the motor like oil switch or something else ?
 

wrench 3

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Aug 12, 2012
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2,108
The main power relay is turned on by the computer. It won't turn it on unless it's getting signals from the crank sensor.
The computer should run the fuel pump for 2 seconds when the key is first turned on but not cranked. Can you hear the pump run for the 2 seconds?
 

wrench 3

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If you're not getting the two second pump run, you need to check the power and grounds to the ECM (computer). There should be three black wires in one of the 24 pin connectors on the ECM. They should all be grounded. The 32 pin connector should have a purple wire that should have 12V when the key is on. All the terminals in the connectors should be clean and tight.
 

Matt musky

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Apr 4, 2017
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Ok so I checked all three black wires and they are all grounded at the 24 pin connector. The purple wire at the 32 pin connector has 11.5v to ground with key on. But the coil of the relay has a 12v positive with key on or off but no negative . I'm stumped
 

wrench 3

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Did you check the main power relay with the engine cranking over?
 

Matt musky

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Apr 4, 2017
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No , but the fuel pump isn't starting with key on . I read somewhere else that one guy had no fuel or air pressure in the rail which cause the main power relay not to close . Does that sound right?
 

wrench 3

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Aug 12, 2012
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2,108
Once the ECM is getting a signal from the crank sensor it will close the the power relay and start the fuel pump regardless of the air pressure.
I'm working from 2001 information but at that time the ECM would close the relay and start the fuel pumps for two seconds when the key is first turned on. But only for two seconds. After that it won't turn the relay on unless it's getting a signal from the crank sensor. (The engine is cranking over)
You can test the wire from the fuel pump to the ECM. But the assumption is that if the ECM has ground and power but isn't priming the fuel system you have a bad ECM. However it would be worth the cost to have a dealer test it with a scan tool.(DDT)
 
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