3.7 no crank

Dschaffer

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I just noticed that there is no ground wire from the choke in the wiring diagram link posted above. My choke has a ground wire. Any idea where it leads to? Thanks I am planning on taking the tape off of that group of wires tomorrow afternoon anyway but maybe the other end of that ground wire is loose? I guess that wouldn’t explain why the wire gets hot even when unplugged from the choke. Never mind. I see it is in the diagram. Pretty much just throwing half baked thoughts out there at this point. Sorry about that.
 

Dschaffer

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Did a little more testing. There are 12.6 volts at the red wire on the ignition switch. When I put the switch to the on position, the purple wire has 11.4 volts. With the switch in the start position, the yellow wire has 11.4. Does this mean I need a new switch?
 

achris

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Did a little more testing. There are 12.6 volts at the red wire on the ignition switch. When I put the switch to the on position, the purple wire has 11.4 volts. With the switch in the start position, the yellow wire has 11.4. Does this mean I need a new switch?

The switch is doing what it should, but those purple and yellow voltages are down. What does the red wire read when you turn the key to ON? (We know it's 12.4 with the key OFF, need to know it's voltage with the key ON)

Chris.....
 

Scott Danforth

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Did a little more testing. There are 12.6 volts at the red wire on the ignition switch. When I put the switch to the on position, the purple wire has 11.4 volts. With the switch in the start position, the yellow wire has 11.4. Does this mean I need a new switch?

the purple wire (standard ignition wire color) on the I terminal of the start switch should have the same voltage that is coming in on the red wire (standard un-switched battery voltage wire color) on the "B" terminal. if you have a voltage drop, you have corrosion somewhere. the same goes with the yellow wire with red stripe (standard Start circuit wire color) on the "S" terminal

this means that you need to clean your terminals and make sure you have good solid electrical connections
 

Dschaffer

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The switch is doing what it should, but those purple and yellow voltages are down. What does the red wire read when you turn the key to ON? (We know it's 12.4 with the key OFF, need to know it's voltage with the key ON)

Chris.....

Red wire/post with key on reads 11.1 volts.
 

Dschaffer

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the purple wire (standard ignition wire color) on the I terminal of the start switch should have the same voltage that is coming in on the red wire (standard un-switched battery voltage wire color) on the "B" terminal. if you have a voltage drop, you have corrosion somewhere. the same goes with the yellow wire with red stripe (standard Start circuit wire color) on the "S" terminal

this means that you need to clean your terminals and make sure you have good solid electrical connections

I am testing at the posts on the back of the ignition switch. Does this mean the drop is in the switch? Thanks
 

Scott Danforth

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could be, or there could be corrosion between the screw and the incoming power wire. clean the terminals and re-test.

if you want to bypass the switch, hot-wire B to I terminal for ignition, then momentarily connect B to S terminal to crank
 

Dschaffer

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could be, or there could be corrosion between the screw and the incoming power wire. clean the terminals and re-test.

if you want to bypass the switch, hot-wire B to I terminal for ignition, then momentarily connect B to S terminal to crank

I cleaned up the ignition switch but am still loosing around 1 volt. I have 12.6 at the red in off, and 11.4ish at the purple when switched on. Fair to say the ignition switch is not functioning properly?
How is it I have 10.6ish volts at the purple wires at the choke but only 1.6ish at the Ignition coil when switched on? Do resistance wires go bad? It has no apparent defects. It something else in that circuit that could be taking the volts? Thanks
 

Dschaffer

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New discovery!!!! I cut the purple ignition wire and the purple resistance wire at the choke, thus separating them. I now have 12.6 volts at the purple ignition wire at choke and at the ignition switch in the on position. So what is happening with the resistance wire that it was taking so much voltage? Even when disconnected from the coil and choke, I was reading 10.5ish volts at the choke side of the wires and 1.5ish volts at the coil side of the wires? Do I simply need a new resistance wire? If so, where do I find one or can I make one? Thanks in advance.
I just had another thought. The resistance wire is connected to the wire that goes to the slave solenoid, correct? Could it be something is up with the slave solenoid that is taking the voltage? Thanks again
 

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Dschaffer

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Ok. I’m about to go crazy. I disconnected the red/yellow wire from the slave solenoid and had 12.6 volts there. So that means the Slave is bad, right? I replaced the slave, got super excited to hear her crank fire and run, turned the key and absolutely nothing happened. I have 12.6ish volts everywhere but the big post on the slave that connects to the little post on the starter. What the F@$%^#@@$$%% is going on!!!! Fair to say all wiring pre slave/starter is good, right?
 

Dschaffer

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I used a NAPA solenoid. Should I order an OEM? Could it be something with the starter? I have a new starter coming next week but the stater worked great, except the gears are stripped, until I put the new slave on.
 
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achris

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Red wire/post with key on reads 11.1 volts.

Key OFF =12.4, Key ON =11.1... You have a resisitive connection BEFORE the key. Work back from the key towards the battery. If you still have a glass 3AG 20A ignition fuse (in the harness connected to the key), that's where I'd be looking next. Check your fuse for corroded ends. Very common problem. If you do find corrosion, cut the 3AG fuse holder out and put a water-proof mini-blade fuse holder in place. I've done that with many boats and fixed ignition problems. I also like those fuses because Merc use them in the MPI engines and the later trim pumps.. Means I only need to carry one type of fuse (of the same value too :)) and I 'spare' everything. I carry a box of 20A mini blade fuses. Job done! Check out my video on marine fuses... (link in my signature)

Chris......

Edit: Even if you don't find corrosion, cut those glass fuses out and put in the mini-blades...

Blade.JPG
 
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Dschaffer

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Key OFF =12.4, Key ON =11.1... You have a resisitive connection BEFORE the key. Work back from the key towards the battery. If you still have a glass 3AG 20A ignition fuse (in the harness connected to the key), that's where I'd be looking next. Check your fuse for corroded ends. Very common problem. If you do find corrosion, cut the 3AG fuse holder out and put a water-proof mini-blade fuse holder in place. I've done that with many boats and fixed ignition problems. I also like those fuses because Merc use them in the MPI engines and the later trim pumps.. Means I only need to carry one type of fuse (of the same value too :)) and I 'spare' everything. I carry a box of 20A mini blade fuses. Job done! Check out my video on marine fuses... (link in my signature)

Chris......

Edit: Even if you don't find corrosion, cut those glass fuses out and put in the mini-blades...


Thank you for the insight but you must have missed the update I posted. When I take the yellow/red wire off of the slave solenoid I get 12.6 volts pretty much everywhere pre-slave. I replaced the slave solenoid but now it does not crank at all. I am at a loss.
 

nola mike

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a) The slave on the 470 is different from most of the other mercs IIRC. Put the old one back on, why did you swap it out to begin with? b) The yellow/red at the slave only sees voltage when the key is in the start position, so that doesn't make sense. Putting the key to run shouldn't do that unless it's wired wrong or you have the wrong part in there.
You're really shotgunning this and not proceeding in a stepwise manner with your troubleshooting. I'm still not clear on what the actual problem is that you were having to begin with.
 

Dschaffer

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a) The slave on the 470 is different from most of the other mercs IIRC. Put the old one back on, why did you swap it out to begin with? b) The yellow/red at the slave only sees voltage when the key is in the start position, so that doesn't make sense. Putting the key to run shouldn't do that unless it's wired wrong or you have the wrong part in there.
You're really shotgunning this and not proceeding in a stepwise manner with your troubleshooting. I'm still not clear on what the actual problem is that you were having to begin with.

With the old/original slave in place, I have 12.6 volts at the ignition (red wire), 11.4 at purple ignition wire (switched on). 10.6 at the purple wire at the choke and 1.4 at the coil. It will crank and fire for awhile but will not stay running when the key goes back to the on position. Also, after cranking a firing for awhile, it will suddenly not crank at all. It’s like I have to give it time to cool or something. When I cut the purple wires at the choke, I discovered that I now had 12.6 volts everywhere. I then reconnected the wires and it went back to 10.6 at the choke and 1.4 at the ignition coil. I removed the yellow red wire from the slave and had 12.6 volts everywhere again (switch, choke, coil) and no smoking wire. That led me to believe that there was something wrong with the slave. I replaced the slave, have 12.6 volts everywhere (switch, choke, coil) but it does absolutely nothing when I turn the key. Does that make sense?
 

Dschaffer

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To be sure, I used the OEM slave solenoid part number on the NAPA site and it showed the one they sold me. They look identical. Maybe I got a bad solenoid? I can order the Quicksilver solenoid for twice the money but I’m not really sure that it is the issue. Is there any chance the trim pump wiring could be giving me these problems? On another note, is it normal to have 12 volts at all the ignition switch posts with the key on (red, purple, yellow/red)? I figured yes to the red and purple but am surprised to see it at the yellow/red. Thanks
 

nola mike

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First: Your problem is a/several bad connections. Lets track them down. Second: Your numbers are meaningless unless you specify what position the key is in when you take them. Third: You need to specify which end of the wire you're measuring. Fourth: I'm assuming all your coil voltages are at the (+) terminal.

With the old/original slave in place, I have 12.6 volts at the ignition (red wire),
Good

11.4 at purple ignition wire (switched on). 10.6 at the purple wire at the choke

Ok, that's the first problem. And there are 2 purple wires at the choke. 1 is the ignition wire, 1 is the resistance wire. You need to track down where you're losing voltage. You have problems in the first leg--either in the switch or (more likely) the connections somewhere between the end of the red wire and beginning of purple. Is this reading from the (cleaned) lug on the switch, or from the terminal on the wire? Disconnect purple, and measure at the switch terminal. 12.6? good, move on. No? then you have a problem with the red connection or the switch.
Problem #2: You're losing voltage between the purple wire at the switch and the choke. This can be be a bad connection, or a problem with the terminal crimped to the wire itself. You can verify anything that you're doing by disconnecting the wire in question and running a direct jumper wire from a-->b and see if you're still getting the voltage drop.

and 1.4 at the coil.
If that's a real reading, your resistance wire is bad regardless of the other readings. Did you say it was smoking? It should be hot, but not smoking. You should be losing 2-3 volts through the resistance wire. With everything off, measure the resistance in the wire if you want. I don't know the specs offhand.

It will crank and fire for awhile but will not stay running when the key goes back to the on position.

That's to be expected if you're only getting 1v at the coil. You need 9v or so. Your coil sees a full 12v from the slave when cranking from the purple/yellow wire.

Also, after cranking a firing for awhile, it will suddenly not crank at all. It’s like I have to give it time to cool or something. When I cut the purple wires at the choke, I discovered that I now had 12.6 volts everywhere.

What does cut the wires mean? Where is everywhere?

I then reconnected the wires and it went back to 10.6 at the choke and 1.4 at the ignition coil. I removed the yellow red wire from the slave and had 12.6 volts everywhere again (switch, choke, coil) and no smoking wire.
That led me to believe that there was something wrong with the slave. I replaced the slave, have 12.6 volts everywhere (switch, choke, coil) but it does absolutely nothing when I turn the key. Does that make sense?
Key position? Yellow/purple wire shouldn't have any voltage unless cranking. You shouldn't have 12v at the coil unless cranking. Doubt this is your issue, i bet you either have the wrong slave or you wired it wrong when you put it back. I'd put the old slave back in.
 

Dschaffer

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First: Your problem is a/several bad connections. Lets track them down. Second: Your numbers are meaningless unless you specify what position the key is in when you take them. Third: You need to specify which end of the wire you're measuring. Fourth: I'm assuming all your coil voltages are at the (+) terminal.


Good



Ok, that's the first problem. And there are 2 purple wires at the choke. 1 is the ignition wire, 1 is the resistance wire. You need to track down where you're losing voltage. You have problems in the first leg--either in the switch or (more likely) the connections somewhere between the end of the red wire and beginning of purple. Is this reading from the (cleaned) lug on the switch, or from the terminal on the wire? Disconnect purple, and measure at the switch terminal. 12.6? good, move on. No? then you have a problem with the red connection or the switch.
Problem #2: You're losing voltage between the purple wire at the switch and the choke. This can be be a bad connection, or a problem with the terminal crimped to the wire itself. You can verify anything that you're doing by disconnecting the wire in question and running a direct jumper wire from a-->b and see if you're still getting the voltage drop.



If that's a real reading, your resistance wire is bad regardless of the other readings. Did you say it was smoking? It should be hot, but not smoking. You should be losing 2-3 volts through the resistance wire. With everything off, measure the resistance in the wire if you want. I don't know the specs offhand.



That's to be expected if you're only getting 1v at the coil. You need 9v or so. Your coil sees a full 12v from the slave when cranking from the purple/yellow wire.



What does cut the wires mean? Where is everywhere?

I posted a picture of the cut wires. I cut the two purple wires just before the choke. When I did this, I got 12 volts at the purple ignition wire at the choke and at the switch, with key on. This means purple wire from choke to switch is good, correct? I then spliced the wires back together and obviously had the same issues. (10.4 volts at the choke and 1.6 at the coil, connected to the coil or not, switch “on” position. I then disconnected the yellow/red wire from the slave solenoid (this wire shares the same + post at the coil as the purple resistance wire), and read 12 at the switch, choke and coil in theswitch on position. I thought this would mean that the slave is causing my issues. When the slave is not connected to the coil, I have 12v at the switch, choke and coil and no smoking wires.


Key position? Yellow/purple wire shouldn't have any voltage unless cranking. You shouldn't have 12v at the coil unless cranking. Doubt this is your issue, i bet you either have the wrong slave or you wired it wrong when you put it back. I'd put the old slave back in.

Summary.
With the new slave installed, I have a little over 12 at the red and purple and a little under 12 at the yellow at the switch (key on). Key position off, I have 12 at the red only.
Everything is wired the same as pre slave swap and verified correct via the wiring diagram. When the yellow/red, wire coming from the coil, was connected to the previous solenoid, I had 10.6 at the choke and 1.4 at the coil and a smoking hot resistance wire (key on). When the yellow/red wire was disconnect from the previous slave, I got 12 volts at coil, choke and switch. That is why I thought the slave must of been bad.


Thanks for the help. Any chance any of you live in Northwest Michigan???
 
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Dschaffer

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I have a new starter coming tomorrow and a new OEM slave solenoid on Friday. I have no idea what else it could be so lets hope for the best. Is there any way a bad slave could damage a new starter? If not, I will put the new starter on when it arrives and re-install the old slave and see what happens. Thanks
 

Dschaffer

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The engine is running! I sure wish I had something more definitive to report in regards to what the issue was. I installed a OEM starter, Slave Solenoid and Coil. After installing the new starter and slave all the volts looked good everywhere and she cranked and even fired briefly but then it would only crank. I thought maybe I had flooded it or bad gas. After giving it some time and adding some fresh Rec. fuel to the carb, she still would not fire. I tested the new (non OEM) coil and sure enough it was no longer sparking. I put the new OEM coil on (that I had tried in previous attempts) and she fired right up and runs as good as she ever has. Is it possible that the problem was the solenoid on the starter? I had replaced the coil and Slave (non OEM) but still had issues. Maybe this motor is very picky in regards to OEM parts? I had replaced the coil last summer with a NAPA and it ran fine for the season but the coil was shot this spring. The NAPA coil I replaced it with apparently died while I was diagnosing the issue. Anyway, like I mentioned, nothing definitive here but if its a possibility, I would guess the solenoid on the starter was an issue. Thanks for trying to help. Happy boating!
 
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