3.0L Merc - Ignition Issues - Only 10 V @ switch

Joined
Sep 29, 2013
Messages
10
Yo,

I've been trying to troubleshoot a no spark ignition problem & am a little confused.

Good solid battery with clean connects & 12.6 V

Good Starter/Solenoid connect with 12.6 V

Good reading at the circuit breaker 12.6 V


Reading at the brand new ignition switch shows only 10 V


I'm going to try cleaning up all the connections @ and around the fuse panel right now.


If cleaning up the connections around the fuse panel & ignition switch fail to correct the problem, I'm not sure where to go next.


Any & all help is much appreciated.
 

airshot

Rear Admiral
Joined
Jul 22, 2008
Messages
4,216
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

There is a bad connection or a bad wire somewhere in the system. On older boats I have seen corrosion inside the wire coating not visible to the eye and found it by lightly bending the wire and feeling the little crunchiness caused by the corrosion. Being a boat...
the bad connection or wire will be in the worst possible location to work on.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

Yo,

I've been trying to troubleshoot a no spark ignition problem & am a little confused.

Good solid battery with clean connects & 12.6 V

Good Starter/Solenoid connect with 12.6 V

Good reading at the circuit breaker 12.6 V


Reading at the brand new ignition switch shows only 10 V


I'm going to try cleaning up all the connections @ and around the fuse panel right now.


If cleaning up the connections around the fuse panel & ignition switch fail to correct the problem, I'm not sure where to go next.


Any & all help is much appreciated.

:welcome: to iboats

Check the cannon connector on the engine. Many times the corrision shows up there. If you have an engne serial number of maybe the year of the engine if real old would help.

Do you have 12V at the + side of the coil?
 
Joined
Sep 29, 2013
Messages
10
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

Thanks airshot & alldodge.

I'm hoping its just a loose/corroded connection. I'm going back out to check the cannon connector & also the + side of the coil for 12 V. I believe last time I checked, the coil was @ 6-7.

20130723_121851.jpg

A331184
 
Joined
Sep 29, 2013
Messages
10
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

Ok. Checked the cannon connector & it looked decent. The reading @ the + side of the coil was 7 V.

Any ideas where I should look next?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

I would start using a 'volt drop' test to find where you're losing the juice...

One of my favourite 'tricks' is a voltage drop check. It checks to make sure that there is no bad connections/voltage loss in a circuit. Most understand about measuring voltage, stick the meter black on a good ground and probe with the red and read the voltage... But if you put the meter leads across the same circuit and dial the reading down to the smallest scale, like 200mV, then you'll be looking at any voltage lost in the circuit.

Example, if you had an electronic ignition. Your coil voltage. We know from the circuit diagram that there should be no 'device' that will use voltage (best way to put it, not completely accurate, but it works) between the battery positive post and the coil + terminal. So, put the red meter lead on the positive post (not the terminal, the post itself) of the battery and the black meter lead on the + terminal of the coil, with the key ON of course. What you should see is a reading of 0, or extremely close to 0. If you have a reading of more than about 50mV, then start looking for a bad connection.

It's a most effective method of finding a bad ground, because you can do it in the negative circuit too. Example. Put the meter black lead on the battery negative post, and the red lead on the body of the starter motor. Now operate the starter motor. See any more than about 10mV, you have a bad connection between the battery and the stater motor. The reason for the lead on the post itself and not the terminal is because corroded terminals are a big culprit. If you suspect a dirty post, just meter between the post and the terminal, it will show up there too.

Chris........
 
Joined
Sep 29, 2013
Messages
10
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

I would start using a 'volt drop' test to find where you're losing the juice...

One of my favourite 'tricks' is a voltage drop check. It checks to make sure that there is no bad connections/voltage loss in a circuit. Most understand about measuring voltage, stick the meter black on a good ground and probe with the red and read the voltage... But if you put the meter leads across the same circuit and dial the reading down to the smallest scale, like 200mV, then you'll be looking at any voltage lost in the circuit.

Example, if you had an electronic ignition. Your coil voltage. We know from the circuit diagram that there should be no 'device' that will use voltage (best way to put it, not completely accurate, but it works) between the battery positive post and the coil + terminal. So, put the red meter lead on the positive post (not the terminal, the post itself) of the battery and the black meter lead on the + terminal of the coil, with the key ON of course. What you should see is a reading of 0, or extremely close to 0. If you have a reading of more than about 50mV, then start looking for a bad connection.

It's a most effective method of finding a bad ground, because you can do it in the negative circuit too. Example. Put the meter black lead on the battery negative post, and the red lead on the body of the starter motor. Now operate the starter motor. See any more than about 10mV, you have a bad connection between the battery and the stater motor. The reason for the lead on the post itself and not the terminal is because corroded terminals are a big culprit. If you suspect a dirty post, just meter between the post and the terminal, it will show up there too.

Chris........

Yo. Thanks for the help Chris.

When connecting the + battery post with the + coil I received a reading of 6.0-6.5 V.

I'm gonna try the starter motor next, but am unsure as what to do after that.
 

stonyloam

Vice Admiral
Joined
Mar 13, 2009
Messages
5,827
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

When you measured the voltage at the switch, what did you use for a ground? It could be that you have a poor ground up under the dash. If you can, try measuring the voltage at the choke connector (switch on) to a solid ground at the engine or battery -. If you have a higher voltage back there then at the switch you have a measurement problem at the switch. Just a guess:confused:. Your voltage at the coil + sounds OK if you have a resistance wire.
 
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Chef Shawn

Petty Officer 3rd Class
Joined
Jul 15, 2012
Messages
87
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

Replace the coil.
 

stonyloam

Vice Admiral
Joined
Mar 13, 2009
Messages
5,827
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

Do you have a points ignition?
 

LorenHaus

Petty Officer 2nd Class
Joined
Aug 6, 2010
Messages
140
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

Points ignition has a ballast resistor built into the engine wire harness to reduce the voltage at the coil.
 
Joined
Sep 29, 2013
Messages
10
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

When you measured the voltage at the switch, what did you use for a ground? It could be that you have a poor ground up under the dash. If you can, try measuring the voltage at the choke connector (switch on) to a solid ground at the engine or battery -. If you have a higher voltage back there then at the switch you have a measurement problem at the switch. Just a guess:confused:. Your voltage at the coil + sounds OK if you have a resistance wire.

When measuring the voltage at the switch I'm now receiving a 0V reading. I tried a couple different grounds when testing, including the one for the fuse panel where it shows 12V.

I have yet to check the voltage at the choke connector & will do that next.
 
Joined
Sep 29, 2013
Messages
10
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

Replace the coil.

I'm not positive, but I think the 6V coil reading is ok with a points ignition & a resistance wire.

Do you have a points ignition?

Yes

Points ignition has a ballast resistor built into the engine wire harness to reduce the voltage at the coil.

Cool. So 6V's at the coil should be ok?
 
Joined
Sep 29, 2013
Messages
10
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

Yo,

I was able to get a 12V reading at the ignition switch, a 6V reading at the coil, but the choke connector is only reading 9-10V.

Could this mean I have a bad connection at the choke?

Thanks
 

dingdongs

Chief Petty Officer
Joined
May 29, 2009
Messages
649
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

the microswitch may be putting your ignition to ground,Have you tried disconnecting the wires that lead to it?
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

Yo,

I was able to get a 12V reading at the ignition switch, a 6V reading at the coil, but the choke connector is only reading 9-10V.

Could this mean I have a bad connection at the choke?

Thanks

There is a bit of a voltage drop going on but I don't see this as the problem. Your choke is ok and there appears to be a ground issue but this could also be with where the ground was taken by your meter.

Remove the distributer cap and crank the engine and determine if the points are opening and closing as the distributer cam rotates. If they are bump the starter until the points are closed. Get a non-metallic tool like a pencil or a screw drive can be used if it only touches the nylon piece the rides on the distributer cam.

With the key to the run position.
Take the tool (pencil) and move the points to open the gap and look for spark.
If no spark is seen close the points and try a few times.
Turn key off, check for continuity between ( - ) side of coil and points. Insure there is zero ohms when the points are closed and greater then when open.
If no spark replace the condenser and try spark test again.

Let us know your findings
 
Joined
Sep 29, 2013
Messages
10
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

There is a bit of a voltage drop going on but I don't see this as the problem. Your choke is ok and there appears to be a ground issue but this could also be with where the ground was taken by your meter.

Remove the distributer cap and crank the engine and determine if the points are opening and closing as the distributer cam rotates. If they are bump the starter until the points are closed. Get a non-metallic tool like a pencil or a screw drive can be used if it only touches the nylon piece the rides on the distributer cam.

With the key to the run position.
Take the tool (pencil) and move the points to open the gap and look for spark.
If no spark is seen close the points and try a few times.
Turn key off, check for continuity between ( - ) side of coil and points. Insure there is zero ohms when the points are closed and greater then when open.
If no spark replace the condenser and try spark test again.

Let us know your findings


Yo guys & gals,

I'm stuck again right now.

So far I've got

12V battery
12V starter
12V circuit breaker
12V solenoid
12V fuse panel
6-7V Coil

0V choke connector
0V microswitch
0V ignition switch

Also the trim up & down won't work. ( they worked great a couple weeks ago & now they don't even click )

When I light up the gauges on the panel the mph one does not light up either.

I still have yet to check the distributor cap.


Is there anything I'm doing wrong? I'm not sure what I should do next?


Any & all help is much appreciated.

Thanks
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

Check your grounds and the big harness connector on the engine...
 
Joined
Sep 29, 2013
Messages
10
Re: 3.0L Merc - Ignition Issues - Only 10 V @ switch

Check your grounds and the big harness connector on the engine...

YO,

Grounds seem to be ok & the big harness has been cleaned & reattached.

Now I'm getting a zero reading at the ignition, no start/crank.

Also the coil is reading at 0V as well.


With Power on, The gauge needles aren't working, put the panel switch turns the gauge lights on

The Center MPH Gauge fails to light up like the others


Any ideas as to what is going on here?

THanks
 
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