Ignition problems! Please help

B

Biglove

Cadet
Joined
Jul 5, 2020
Messages
7
I have a 1998 5.7l mercruiser efi. Don't now the ser# off hand. I'll try to keep this as short as possible. Two weekends ago my boat started idling rough after a 30 minute cruise. Got it to a mooring where it died and wouldn't start for some time. Got it going and planed out back to dock where it died at idle. Replaced iac valve and eventually starter.(brand new) I assume I screwed the starter. Worked fine for half and hour when back on the water. Started idling rough again but would plane out no problem. Then all of a sudden lost power. Got 3/4 back to dock and died and won't start. Sounds like the starter isn't fully engaging and won't turn the motor. As a test I turned the kill switch off and the starter engages and turns the motor no problem. Turn the kill switch on and again starter won't engage. I assume either fuel pump or ignition is drawing down the voltage not allowing the starter to fully engage. How do I start trouble shooting with no running engine. Tia

Brian
 
R

ROY WILLIAMS

Chief Petty Officer
Joined
Aug 8, 2022
Messages
400
Biglove said:
I have a 1998 5.7l mercruiser efi. Don't now the ser# off hand. I'll try to keep this as short as possible. Two weekends ago my boat started idling rough after a 30 minute cruise. Got it to a mooring where it died and wouldn't start for some time. Got it going and planed out back to dock where it died at idle. Replaced iac valve and eventually starter.(brand new) I assume I screwed the starter. Worked fine for half and hour when back on the water. Started idling rough again but would plane out no problem. Then all of a sudden lost power. Got 3/4 back to dock and died and won't start. Sounds like the starter isn't fully engaging and won't turn the motor. As a test I turned the kill switch off and the starter engages and turns the motor no problem. Turn the kill switch on and again starter won't engage. I assume either fuel pump or ignition is drawing down the voltage not allowing the starter to fully engage. How do I start trouble shooting with no running engine. Tia

Brian
Click to expand...
the gasoline fuel filter ... also the fuel pump and the carb doing the cleaner throttle body ... the gas tank is the venting cleaning it ..
also cleaned the distributor and the rotor ....
 
B

Biglove

Cadet
Joined
Jul 5, 2020
Messages
7
Done all of the above. Took it to the mechanic and he is getting code 42 for ignition timing. Changes ignition control module with same result. Still getting code 42. Again, tune up has been completed. Vent is clear, removed anti siphon valve last year as it failed. Any thought on timing issue? Could faulty tachometer cause issues? Seemed to jump around alot while the boat was failing. I mean it was dancing.
 
alldodge

alldodge

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Staff member
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Mar 8, 2009
Messages
42,059
Check for 5V with ignition ON, motor OFF
Check on one of the 5V sensors like MAP, TPS, Temp
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
49,563
Do you have the original 2-wire ignition sensor? May want to upgrade to the 3-wire
 
B

Biglove

Cadet
Joined
Jul 5, 2020
Messages
7
Narrowed it down to the ecm. Anyone know of anyone that might have one that won't break the bank. Part# is 861542t03.
 
Q

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,342
I’d be checking the earths around the wiring. Check that starter relay and the ignition wire integrity at the engine. There is a fuse around there too, on the efi. From memory. Not sure though. I’d also test the ignition switch at the key too.
 
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