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b84 Mercruiser 470 cranking problem

a1nowell

Contributing Member
"I am having a cranking proble

"I am having a cranking problem. I have a rebuilt starter and solenoid that has cranked the engine beore. When I jump between the battery post on the solenoid to the (yellow-red wire) post on the solenoid the engine will crank. The ignition switch is new and test good. I have tested the shift interrupter switch and it test good. I have tested all circuits all the way from the ignition to the starter slave solenoid and all test good. I have tested all circuits from the starter solenoid to the slave solenoid (yellow red wire)and they test good. At the starter slave solenoid if I jump from the yellow red post to the other yellow red post and then hit the key it will crank. Does this imply the starter slave solenoid is bad? That is my conclusion but I would like some sage advice, electrical is still a mystery to me."
 
I would try a new Solenoid. I

I would try a new Solenoid. I have burned a solenoid out once that was only a week old. I was told by B ans M starters in Mpls. that a weak battery can kill a solenoid.
 
"L Hoover is right. When all

"L Hoover is right. When all is working, you would do yourself a favor by testing for voltage drop along various points in the starting circuit.

Use a digital volt meter and test each wire connection to ground. Start w/the battery for a reference voltage. For all the wires that are 14 ga. or less, if you find a drop in voltage of 0.02 or more, clean the connection and retest. If it stays the same then replace the wire connector and/or the wire.

Your wiring is 25 years old and probably has a number of wires where the copper is blackened. Scrape the wire ends w/a piece of emery cloth until the copper is bright to improve current flow. Soldering the connector makes a solid connection."
 
"L Hoover & Guy Gasper ,

"L Hoover & Guy Gasper ,
Thanks for the insight. Guy I will run the voltmeter test as you suggest.

Larry"
 
You are messing with high curr

You are messing with high current that can weld a screwdriver to a stud. You are referring to the solenoid at the main circuit breaker and not the one attached to the starter?

If the starter will not engage when you turn the ignition key to START; BRIEFLY jump the two large studs on top of the SLAVE solenoid to see if the starter engages. If it does engage then attach a test lamp to the yellow/red stripe wire on the front of the solenoid and turn the key to start. If you get 12 volts and the starter won't engage; replace the slave solenoid.
 
I am asking about the slave so

I am asking about the slave solenoid attached to the side of the block not the one on top of the starter.
 
Test it. Is your battery full

Test it. Is your battery fully charged? If the solenoid has a blackened stud the internal contactor is burned. Replace the solenoid. DISCONNECT THE BATTERY FIRST.
 
New problem but I think they a

New problem but I think they are all related.

I have installed the new slave solenoid and have it connected correctly. I can now crank and start the engine. But the engine dies when the key is moved from the start position back to the run position. If I jump a wire from the positive post on the battery to the positive post on the coil the engine will continue running. I have tested the purple wire that runs from the coil to the slave solenoid and the voltage is good. Any suggestions?
 
"What is the voltage reading o

"What is the voltage reading on the coil + stud w/the key in the run position? It should be 5 to 8 vdc. The resistor ballast wire drops the 12 vdc to the lower voltage. If there is "0" vdc there w/the key in the RUN position, the problem is EITHER in the resistor wire and/or its connectors or the ignition key is not sending 12 vdc in the RUN position.

Look for bad wires/connections on the switch. If the resistor wire is bad you must replace it w/a resistor wire or use an external ballast resistor on the coil. Run 12 vdc to one side of the resistor and the other side to the coil. OR just convert the points to Pertronix Electronic ignition."
 
"Guy,
Thanks for your help.


"Guy,
Thanks for your help. Your suggestions help me track back into the new console I had put in during this old pontoon boat rebuild. And I figuried out I had wired the ignition wrong which resulted im buring out the slave solenoid and the new ignition switch. All is corrected now and this old 470 starts and is running great for setting in a field for five years.

Thanks again for your help."
 
"This old '84 JC Tritoon i

"This old '84 JC Tritoon is just about finished being rebuilt. The engine starts and runs pretty good and after some tedious time I have all the wiring redone. All of my new guages are working but my voltage guage is barley registering 12 volts. I put a volt meter on and the old Rotor Altenator is putting out 11.89 volts. If I turn on all light etc, it still puts out 11.89 volts. Does anyone have any suggestions how I might get another 1 to 2 volts out of this altenator?

If I have to replace the altenator any suggestion on which conversion kit comes with all brackets, pulleys etc?"
 
Make sure you have clean groun

Make sure you have clean ground wire connections. But it sounds like your alternator has a rectifier open. Alt. conversion kits are sold on eBay.
 
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