Starting issue

[calvinallen88]

Mercruiser 165 I6, now starts but dies as soon as I move key from start to run position. I have googled but cannot figure how to diagnose this. Does it sound like a weak coil? Faulty ignition switch?

I pulled the switch and wires are corroded but intact. Just checked and in off position have 12v on one wire. In Run position have 12v on two wires. And since starter turns in start position I assume I have 12v on 3 wires in start position.

 

[Scott Danforth]

its almost never the coil only about 3 out a a million changed coils are actually bad. people replace the coils because they think its the problem without doing actual troubleshooting.

the issue is one of the following things:

• a corroded wire. Solution here is to clean all corrosion. or replace the wires
• faulty ignition switch. solution here is to test and if determined to be bad, replace the ignition switch
• bad resistor wire feeding the coil (during cranking, the coil gets its voltage from the starter). Solution here is to test voltage at the coil with just the key on. should be about 9 volts

 

[calvinallen88]

its almost never the coil only about 3 out a a million changed coils are actually bad. people replace the coils because they think its the problem without doing actual troubleshooting.

the issue is one of the following things:

• a corroded wire. Solution here is to clean all corrosion. or replace the wires
• faulty ignition switch. solution here is to test and if determined to be bad, replace the ignition switch
• bad resistor wire feeding the coil (during cranking, the coil gets its voltage from the starter). Solution here is to test voltage at the coil with just the key on. should be about 9 volts

Thanks for the reply. Switch appears to be good. Just rechecked voltage at coil in RUN position and appears to only have 2-3v. Which wire would be resistor wire? How to I test further? Also, looking at the current coil is says "use with primary resistor wire or external resistor". A spare coil that was in the boat says "No external resistor required". Which one is recommended for use?

 

[calvinallen88]

Thanks for the reply. Switch appears to be good. Just rechecked voltage at coil in RUN position and appears to only have 2-3v. Which wire would be resistor wire? How to I test further? Also, looking at the current coil is says "use with primary resistor wire or external resistor". A spare coil that was in the boat says "No external resistor required". Which one is recommended for use?

Also, found that leaving the key in run position I build approx 5v on + side of coil. Reading is the same at R post on starter solenoid. What feeds the R post? I have 12v leaving the starter switch. Would this indicate a bad starter solenoid? I just took apart and cleaned all contact in solenoid last night.

 

[calvinallen88]

So took apart starting solenoid again and cleaned inside. I cannot figure out why I am not getting power to R terminal because the base of it contacts the copper ring same as the red power wire. Maybe a bad post inside the solenoid? Any help is appreciated.

 

[kenny nunez]

If you replace the solenoid try to get a new one rather than a rebuilt. The rebuilts are mostly rebuilt overseas with junk quality parts.

 

[calvinallen88]

UPDATE:
Was able to jump 12v from battery to pos terminal on coil and it started and ran good then cut off after approx 5 sec. So after confirming running I am more motivated in finding short in wiring.

 

[Pruno]

May seem silly, but did you check to make sure the kill switch (if there is one) is in the run position? I just had the exact issue you described happen to me yesterday trying to start, runs in start, but cuts off as soon as key goes to run. I looked at the switch and it looked like it was in run. Tried in vain to start it for several minutes until I finally pushed the switch up and I could feel the click. Then fired no problem. I blame my helper...he can't even wipe his own butt.

 

[calvinallen88]

May seem silly, but did you check to make sure the kill switch (if there is one) is in the run position? I just had the exact issue you described happen to me yesterday trying to start, runs in start, but cuts off as soon as key goes to run. I looked at the switch and it looked like it was in run. Tried in vain to start it for several minutes until I finally pushed the switch up and I could feel the click. Then fired no problem. I blame my helper...he can't even wipe his own butt.

I checked that. Made sure the kill switch was pushed in, then unplugged both wires from switch and connected them together bypassing switch. Same problem. But I will check it again.

 

[calvinallen88]

UPDATE:
Cleaned main harness and engine now starts and runs as normal. Thanks for recommendations guys.