3.0 start no stop

[sandmantoy]

I am repairing a boat for a friend and it sat for a long time, we have rebuilt or replaced almost every component short of the long block. We have everything running and working nice. you just turn the key and it fires right up and purrrr's but when you turn the key off it keeps running. All wire connections are good tested with a meter all plugs cleaned and greased. When key is off we have it narrowed down to you unplug the alternator and it stops and ingnition wire goes dead. I have tried 2 new alternators still the same. I have also disconnected the main harness from the back side of the motor after turning the key off and it still runs. I think the alt. is keeping the ignition wire live but don't understand how and why it is. Has anybody ran into this before? If not we are just going to fill the boat with BEER and dround ourselfs in it. Hey we even got the wives to buff and wax the outside of it. Please some one save us !!!<br /><br />Run a ground hard in the back yard

 

[sandmantoy]

Re: 3.0 start no stop

87 regal 20 footer mercruz 3.0 primary use diving, fishing and takin the girls out for a ride...

 

[tommays]

Re: 3.0 start no stop

i would put a meter to the coil when the motor is stoped and every thing is hooked up and check the volts which i would guess has power if the motor does not stop with the key off.<br /><br />the next thing i would check is the ingition switch if i had to guess i would think it is allowing power to the coil in the off position if not you will have to see what you may have connected up wrong during the repiars as the power has to pass through the ingition switch<br /><br />good luck and let us know how it turns out<br />tommays

 

[sandmantoy]

Re: 3.0 start no stop

We put new ignition key swich in. still stays running with the main harness disconnected isolating the motor by itself.one ignition wire one motor from main harness, it goes from key sw. to coil to starter selinoid to choke and to altinator exciter wire. disconnected starter ing. charged wire still running, disconnected choke still running. if i disconnect coil it will stop but that is what the key should do. If I disconnect the alternator it will stop running with key off. It will not stop running by unpluging alt. with key on. test light conferms ign.on off with key. mercruz book wiring shows resister wire going from coil to choke, only thing not new. No wires have ever been worked on since new too. we have been chaseing corrosion through out the mechanical systems from salt water use and I have untaped and looked for a bad splice from key back.<br /><br />We are now changing the name of the boat to Christeen and lookin for an excorsist...

 

[tommays]

Re: 3.0 start no stop

let me try one more time with the motor off and every thing pluged in like it should be do you have power to the coil or do you only get power all the time after the motor is started<br /><br />tommays

 

[sandmantoy]

Re: 3.0 start no stop

Everything pluged in key off no power to coil. key on power to coil. motor started key on unplug coil motor dies. test light is bright and you can see the distributor pulse. by accedent I grounded out the test light probe while checking power at the choke while the key was off and the motor died. there is no voltage drop when key is switched off when motor is running. motor off- key on 12 volts, key off no voltage I have pulled and tried to see if I could make a wire harness act up but nope. I have another coil I will try tonight. Thanks I have to joke cause I fix things most don't have a clue but this one has me good I just about torchered my friend thinking he messed up wireing or something but the boat is really unmolested mechanicaly. thanks

 

[qystan]

Re: 3.0 start no stop

Possibly the resister bypass wire from the starter to the ignition coil is connected to the wrong starter terminal. It should not be the same as the terminal connected to the alternator and battery.<br /><br />This should be the purple/yellow wire if Merc uses the same convention as the 5.7 engine.<br /><br />If correctly connected, disconnect the purple/yellow and see if engine kills when you turn the ignition off. If that happens then the contactor in the starter is shorting.<br /><br />Let us know the outcome.

 

[sandmantoy]

Re: 3.0 start no stop

I put in new coil today still wont shut down. I did check purple yellow wire same as you suspected but starter was replaced after testing contactor just incase corrosion might be a problem also. but that wasen't it. today we disconnected purple wire from the key sw. and ran a jump wire to engine hooking up only coil and alt, all other connections were un hooked not including battery hot wires. Then started motor by jumping starter fired right up then we cut power to coil and alt motor still runs, then disconnected battery. Motor still runs, the only wires still connected were the alt and coil. Alternator is definetly feeding the coil (crap!!) I cut the exciter wire which would be the purple ignition wire and motor stopped. We tryed a new alt. and still the same. Then friend tells me he has old alt, It is different then alt on motor now but said alt we suspect on motor has been there for 2 years and worked fine. alt now on motor looks like GM internal regulated average car or truck alt. but with fancy marine cover and screens. Other old alt looks like a mitsubishi alt. with a regulator bolted on the back, both are definetly marine grade parts and both are pictured in the repair manual. We are going to go get new alt. like old alt. and install it tomorrow if it fixes this problem I am going to tie friend to a tree and drink all his beer too.

 

[qystan]

Re: 3.0 start no stop

Your problem is power getting to the coil when the ignition switch should have cut that off. As all parts seems to be working and th eonly things disturbed are connections, I believe problem lies in incorrect connections.<br /><br />Not trying to be a smart a* here. I know you did mention that you've tried some of this. One more shot at this.<br /><br />From the wiring, there are 2 ways to get power to the coil, <br />1. the ignition switch <br />2. the resistor bypass wire between the starter and the coil<br /><br />Try this.<br /><br />Disconnet the yellow/purple wire from the coil terminal. Ign switch off, is there 12V at the wire? Should be none, if yes, the other end at the starter is connected to the wrong terminal.<br /><br />If no, is there 12V at the coil purple wire. If yes, disconnect the engine plug, still there? If no, the problem is in the boat wiring, but you have already done with your engine running. If yes, the other end at the alternator is on the wrong terminal. <br /><br />The starter supply terminal (the large wire terminal) should have 3 wires, from battery, from alternator output and wire to the circuit breaker. Correct?<br /><br />There is a red/purple wire at the alternator, it should not be sharing its connection with anything.

 

[sandmantoy]

Re: 3.0 start no stop

I have checked the yellow/purple wire at the starter selinoid and it is on correct side and I did disconnect it after shutting off the key and in this order main harness connector on motor, purp/yellow wire at starter selinoid. starter supply terminal correct, alt output correct. alt wires good, I have traced from end to end and checked with meter to see if the had short some were I could not verifie. Is there a diode in the alt that my be burned out or specific to marine alternators? The alt is charging, I disconnected battery feed to alt and jumped it to alt output and jumped exciter wire (ign 12v) so I could connect and disconnect for test it. im going to put a diode on it just to see tommorow to see for sure if it is feeding back through excite wire.

 

[seahorse5]

Re: 3.0 start no stop

Now you are thinking!! The sense wire or wires from the alternator have to be diode protected to keep alternator juice from flowing back to the coil.<br /><br />If you are using automotive parts, such as the alternator, then you are creating a hazardous condition, and in violation of Federal Law.

 

[sandmantoy]

Re: 3.0 start no stop

It was not an automotive altenater, it resembled a car or truck alternater the difference only being this bad diode I discovered and fixed and the mesh screen and shielding. Oh yeah and the coating zinc chromate paint, I think is the type. I had suspected the alternater through my tests but did not understand until I read your hazardous condition statement Seahorse. Makes sense in a boat, less wireing too. Thanks Guy's