Tb IV intermittent spark ?$#???

[mrzooom]

Ok, I'll keep short...having gone threw and cleaned and filed every connection, I get spark and then I don't get spark??? Checked the compression 150 on all 8 +/- 1 pt., I've got fuel...fresh fuel, fresh battery charge...I get voltage at + coil in run poss. Then it goes away. I haven't checked alternator wire under housing in back...I have not yet tried without tach wire connected to gage...
I just thought about the fact that my tach gage shows opposite of how it should appear. It runs in a CClockwise direction or so it seems,. I'll check in the am and report back...am I over posting here as I do have earlier posts????

 

[Bondo]

Ok, I'll keep short...having gone threw and cleaned and filed every connection, I get spark and then I don't get spark??? Checked the compression 150 on all 8 +/- 1 pt., I've got fuel...fresh fuel, fresh battery charge...I get voltage at + coil in run poss. Then it goes away. I haven't checked alternator wire under housing in back...I have not yet tried without tach wire connected to gage...
I just thought about the fact that my tach gage shows opposite of how it should appear. It runs in a CClockwise direction or so it seems,. I'll check in the am and report back...am I over posting here as I do have earlier posts????

Ayuh,..... Key switch,..??

 

[Scott06]

Ok, I'll keep short...having gone threw and cleaned and filed every connection, I get spark and then I don't get spark??? Checked the compression 150 on all 8 +/- 1 pt., I've got fuel...fresh fuel, fresh battery charge...I get voltage at + coil in run poss. Then it goes away. I haven't checked alternator wire under housing in back...I have not yet tried without tach wire connected to gage...
I just thought about the fact that my tach gage shows opposite of how it should appear. It runs in a CClockwise direction or so it seems,. I'll check in the am and report back...am I over posting here as I do have earlier posts????

given tach comments disconnect the tach wire at coil and see if issue gies away.
a faulty tach can kill spark

 

[mrzooom]

Thanks gentlemen!

 

[nola mike]

given tach comments disconnect the tach wire at coil and see if issue gies away.
a faulty tach can kill spark

I think he's saying he's not getting 12v at the pos coil, which wouldn't be an issue with the tach. Do you have power to the gauges the whole time or do they drop out as well?

 

[mrzooom]

I wasn't paying enough attention when cranking but I will today.
This thing is saturating me with stuff I would never get involved with however, I am learning a lot. Today +/- battery cables I noticed were dark, corroded etc. So I replaced them only to find myself looking at the trim pump and had to go through all of those and clean up contacts etc.
Did all that then realized the green/why wires at cap were not tight enough so since the two nuts there have eroded away the threads on that post are stripped, I can't get them secure I need to replace sensor I guess unless they can be soldered? Please advise!?!

 

[mrzooom]

I tried both ways with tach on and off the coil, but need to complete the clean up first I would imagine. I keep uncovering areas I can't just ignore as I am becoming more aware of how interdependent each wire is upon the next. I never thought or saw it this but then I didn't know any better. But I am becoming more so with every discovery.

 

[nola mike]

I wasn't paying enough attention when cranking but I will today.
This thing is saturating me with stuff I would never get involved with however, I am learning a lot. Today +/- battery cables I noticed were dark, corroded etc. So I replaced them only to find myself looking at the trim pump and had to go through all of those and clean up contacts etc.
Did all that then realized the green/why wires at cap were not tight enough so since the two nuts there have eroded away the threads on that post are stripped, I can't get them secure I need to replace sensor I guess unless they can be soldered? Please advise!?!

Sounds like you have the old style sensor. Won't cause you to lose 12v at the coil pos but for sure will cause you to lose spark. Replace it, and suck it up and buy OEM (I might give Mallory or Sierra a shot, but am probably in the minority). But stay away from no name Amazon sellers.

 

[Scott06]

I think he's saying he's not getting 12v at the pos coil, which wouldn't be an issue with the tach. Do you have power to the gauges the whole time or do they drop out as well?

Yes missed that the power is dropping out, would not be the tach dropping 12 v . But it tach is reading wonky would leave it disconnected anyway

 

[mrzooom]

Can one solder the green/wht distributor wire post where connected to the sensor at base of cap?
I mean is there any issues with my trying to do that?

 

[nola mike]

Can one solder the green/wht distributor wire post where connected to the sensor at base of cap?
I mean is there any issues with my trying to do that?

The issue is that your sensor is the more unreliable type to begin with, can leave you stranded, and is unfixable on the water. Might work, might not, might work for a while.

 

[mrzooom]

Ok, now I have no spark still and now no power to gages...either. I'm thinking I'll pick up a new sensor this week as well as new cap, gasket, and rotor wheel...I do have a couple of other plug in harnesses for boat side to gage panel If need I could always resort to one of those as well, although they came out of an older 140 & 160 laying around. Not sure if they cross apply or not. I'm confident one of you blokes could point me in right direction at that time of all else fails! Mind you I have 12+ volts at coil and to red/wht wire on the dizzy... I'm even starting to sound like you old sea-dogs ;~}

 

[Scott06]

Ok, now I have no spark still and now no power to gages...either. I'm thinking I'll pick up a new sensor this week as well as new cap, gasket, and rotor wheel...I do have a couple of other plug in harnesses for boat side to gage panel If need I could always resort to one of those as well, although they came out of an older 140 & 160 laying around. Not sure if they cross apply or not. I'm confident one of you blokes could point me in right direction at that time of all else fails! Mind you I have 12+ volts at coil and to red/wht wire on the dizzy... I'm even starting to sound like you old sea-dogs ;~}

If u now consistently have 12v at coil go through the thunderbolt troubleshooting guide in stickies

Get an oem merc sensor …

 

[04fxdwgi25]

TSB 92-11 TB4 Troubleshooting guide

 

[mrzooom]

Any suggestions as to where I might shop for an oem sensor?

 

[Scott06]

MerCruiser Engine & Stern Drive by Engine Model

Lookup MerCruiser engine & stern drive by engine model and buy discount parts and accessories from our large online inventory.

www.marineengine.com

they also have a page where you can drop your engine serial number in

MerCruiser Engine & Stern Drive by Engine Model

Lookup MerCruiser engine & stern drive by engine model and buy discount parts and accessories from our large online inventory.

www.marineengine.com

90% sure there is only one TB distributor sensor which is here and has the rig terminal connectors to adapt it for an older dist

Mercury Quicksilver 87-892150Q02 - Ignition Sensor Assembly

Visit MarineEngine.com for Mercury Quicksilver 87-892150Q02 - Ignition Sensor Assembly E11-0005 price, stock and delivery options to order online.

www.marineengine.com

 

[mrzooom]

I think he's saying he's not getting 12v at the pos coil, which wouldn't be an issue with the tach. Do you have power to the gauges the whole time or do they drop out as well?

Yep, no power to the gages either...so, I thought I would start with the sensor?

 

[mrzooom]

Thanks gents, I'll report back!

 

[nola mike]

Any suggestions as to where I might shop for an oem sensor?

Yep, no power to the gages either...so, I thought I would start with the sensor?

No, end with the sensor. If you aren't getting power to the coil, nothing's going to work. (The troubleshooting guide would have stopped you at step 1 if you had looked at it). You need to trace your wiring and see where you're losing power. Start at the ignition switch.

 

[mrzooom]

Sorry for the confusion. Imy getting confused as well. I am getting 12 volts to coil w/key in "on" position. Usually.
Well somehow it all got lost in translation...I had no power at switch. Replaced it. Went through all connections and cleaned every surface of each contact and re-connected. Replaced starter, battery cables, ignition amplifier harness, cleaned shift interrupt switch, added a new coil, verified appropriate wires/firing order, full battery charge.
I found 12+ volts at coil +. Tack was bouncing around but it cranked and even fired a couple of times. Had spark and fuel. But next time...no spark. Disconnected tack wire nothing. Went up to circuit breaker/module (?) Cleaned those as well. Checked compression at that point, 150 +/- 1 -2 all 8 cylinders. Green/red to and from dizzy lose... striped post. Cleaned it, re-nutted it secure (as much as I could).
So thought, maybe it time for a new one (after removing, cleaning, and replacing). So I am about to order sensor. Should I order new cap, wheel, and rotor at the same time?

Standing by...