Not getting Spark on '86 3.0l Alpha 1

[Steveu23]

Re: Not getting Spark on MCM170 Alpha 1

Probably not the wire, more likely the tach itself. Hook the wire back up to the coil, then remove the gray wire from the tach. If it starts, the tach is shorted to ground internally.

It's odd that none of us even gave the tach a mention. It's usually one of the first things we should suggest you check with a no spark condition. (along with the shift interrupt switch, also not mentioned)

I know this is an older post, but can you discuss the possible shift interrupt issue. I have a similar situation, but I DID remove the tach wire from the coil to see if that would work and it didn't. Mine is a 1986 3.0 140 HP Block Tag is B484261. As the original poster did, I ran a hot wire direct to the + coil terminal and it fired right up. That being the case we can't live with it this way.

 

[Bt Doctur]

shift interupt ONLY works coming out of gear to stall the motor, cause a miss to allow the dogs to release,If activated it will kill spart, By having it run hot wired means you lost the 12v from the "I" on the switch to the main harness connection

 

[Steveu23]

I'm going to start a new post. I jumped on someone else's and I created confusion. Sorry folks, long time boater here, with short time posting experience.

 

[Bondo]

I'm going to start a new post. I jumped on someone else's and I created confusion. Sorry folks, long time boater here, with short time posting experience.

Ayuh,..... No need,... Now you've got yer own thread here,.... I changed the title to match yer motor,....

 

[dubs283]

You need to familiarize yourself with a (guessing) conventional/ points ignition

There's a couple write ups in the stickies about function, troubleshooting and tune up

 

[Steveu23]

Hey all first Bondo thanks for course correcting my thread! I'll go over what I've done so far on my points ignition 1986 Mercrusier 3.0 engine serial number is b484281 to try to solve this.
1) sanded all terminals and tightened.
2) checked battery, it fully charged and showing 12.5 volts.
3) checked battery connection at starter and it also showed 12.5 volts
4) checked the smaller solenoid connections under breaker button also showed 12.5 volts
5) checked yellow/red wire on the actual starter solenoid showed 12.5
6) finally tested purple/yellow wire actual on the actual starter solenoid and that only maxed to 9.6 Volts.

Since #6) seems to be where the trouble starts I'm wondering if the obvious answer is to just replace the solenoid. I'm also wondering if there is a chance that I should try swapping the the wires meaning, yellow/red on the outside away from the engine and the purple/yellow on the inside, or closest to the engine.

I've attached some pics just in car something jumps out that I am missing.

 

[dubs283]

For an '86 that 3.0 L is clean.

Seeing only 12 volts on the opposite primary starter solenoid post I'd think the solenoid is bad.

Pics show a most likely replaced starter assembly, best to remove and inspect/replace as necessary

 

[Steveu23]

For an '86 that 3.0 L is clean.

Seeing only 12 volts on the opposite primary starter solenoid post I'd think the solenoid is bad.

Pics show a most likely replaced starter assembly, best to remove and inspect/replace as necessary

Thanks I like a tidy work environment

I'm seeing 12.5 volts on the yellow/red solenoid post, what should that be reading?

Correct on the starter, I just recently installed this just before we dropped the engine in the boat. Which is why I'm a bit confused on possibility of a bad solenoid, but it is what it is. I also bought this starter last fall in anticipation of this rebuild so returning it is probably out of the question at this point.

Thanks for your input.

 

[Bt Doctur]

On the starter it will be "0"volts On the slave it will be "0" vo;ts until the key is in "start" position The Red/purple should have 12 volts on it.
But that is not your problem Do you have 12 volts on the electric choke ? If yes and no volts on the purple wire on the coil your resistance wire is bad.

 

[Bt Doctur]

 

[Steveu23]

On the starter it will be "0"volts On the slave it will be "0" vo;ts until the key is in "start" position The Red/purple should have 12 volts on it.
But that is not your problem Do you have 12 volts on the electric choke ? If yes and no volts on the purple wire on the coil your resistance wire is bad.

I haven't checked the choke as I didn't think that would keep the coil from sparking. I'll rig a wire from the + terminal on the coil to the choke (and disconnect the existing one) when I get home from work tomorrow. Thanks for this. I will keep you all posted with my results, tune in this time tomorrow

 

[Steveu23]

This set up is a little different than the 3.0. But I see the broken line purple wire is what you are referring to. The only concern that comes to mind is that on the 3.0 the purple wire seems to branch from the coil with one branch going to the choke and the other to the alternator. Do you have any thoughts or concerns on that ? I've attached the wiring diagram for this particular engine so you can see what I mean. Apologies on the quality this was printed a year after I graduated HS I think

 

[Steveu23]

This set up is a little different than the 3.0. But I see the broken line purple wire is what you are referring to. The only concern that comes to mind is that on the 3.0 the purple wire seems to branch from the coil with one branch going to the choke and the other to the alternator. Do you have any thoughts or concerns on that ? I've attached the wiring diagram for this particular engine so you can see what I mean. Apologies on the quality this was printed a year after I graduated HS I think

Actually due to the condition of that manual I scanned the whole thing. Here is a better image w/ the solid purple resistor wire path(s) highlighted with red arrows

 

[Steveu23]

I haven't checked the choke as I didn't think that would keep the coil from sparking. I'll rig a wire from the + terminal on the coil to the choke (and disconnect the existing one) when I get home from work tomorrow. Thanks for this. I will keep you all posted with my results, tune in this time tomorrow

Sorry for the lack of an update, we got drenched here in this neck of the woods yesterday. Unfortunately, I have to report that I ran a new purple/yellow wire from the starter to the + coil post because as you are probably aware the purple/yellow wire and solid purple resistance wire are attached on the circle connector on that + post. I then ran a new purple wire from the + coil post to the electric choke and incorporated a branch to go to the alternator. The result was the same, except this time I did take a voltage reading at the choke connection and that only read 8.5 volts when engaging the ignition key and having the engine turn over and 0 (zero) when simply switched to the ON position. I do appreciate any further insight that you may have. I did also order a main starter solenoid on Sunday which will hopefully be here tomorrow.

 

[Scott Danforth]

Service the points.

It's a 3 minute job that includes drinking a beer

 

[Steveu23]

Service the points.

It's a 3 minute job that includes drinking a beer

These are new points, wires, and distributor cap. Two beers 5 minutes Do you know if the terminal on the stater solenoid should be kicking out at least 12V ? Mine is only kicking out mid-high single digits, everything before that point is over 12. Even if it were the points would it affect the solenoid since in the flow of current the points are downstream?

 

[Steveu23]

Happy Friday All, based on all your feedback I'll be installing these this afternoon as the no cost purple resistor wire fix didn't work for me. What the heck it's only money and time, and I'm a moron for owning boats..... no I'm not I love this who am I kidding

 

[Steveu23]

Happy Friday All, based on all your feedback I'll be installing these this afternoon as the no cost purple resistor wire fix didn't work for me. What the heck it's only money and time, and I'm a moron for owning boats..... no I'm not I love this who am I kidding

Skunked again. Tomorrow I will work back from the ignition at the helm and work my way back. Maybe I'm looking at this all wrong. I did have this engine running in my garage out of the boat by jumping the #5 & #6 female (engine side)pins in the harness connector and adding a hot wire to the + side of the coil as the it would start from the starter or the switch from the #7 pin. I even swapped out the old harness with one that I knew worked to make sure that it wasn't the harness. The firing order on this engine is the normal 1-3-4-2 but the engine rotation says CCW instead of the typical LH. I always thought on Mercruisers the CCW (counter clock wise) was a function of the outdrive, but it is it possible it has some effect on the wiring ?

 

[Scott Danforth]

All 3.0 liters are LH fork truck motors. Some are just used in boats.

Did you set dwell to 30 degrees?

 

[Steveu23]

All 3.0 liters are LH fork truck motors. Some are just used in boats.

Did you set dwell to 30 degrees?

I gapped to .22 but I did not check the dwell angle for degrees. I've never done that it just always worked. I'll try that tomorrow. Thank you