on and off SPARK

[dgopetactical]

1987 mercruiser 5.7 alpha 1 thunderbolt ing.

changed manifolds risers, plugs,cap,wires,rotor,carb

started it yesterday for the first time with above items took 5 minutes to start. Ran ok i started to adjust the carb and then I ran out of time.

today i tried to start it and it would not start,strong smell of gas and inside of carb was wet. pulled a plug wire and put a plug on it and cranked it and there was NO spark. There is power to the coil. Im confused. the only thing I noticed was when I replaced the cap and rotor that the sensor was rusted, I got most of the rust off with sandpaper(would this cause intermitent spark?) can somebody point me in the right direction. Im new to the boat do it your self thing and learn most of it on this site and manuels when I can understand them.
thank you so much,
Denny

 

[dgopetactical]

Re: on and off SPARK

still working on this, cleaned all connections still no spark. trying to understand my manual. on the coil there is 2 seperate nuts side by side with wires on them. with the key on im getting voltage out of both studs. if im reading the manual correctly one is positive and one negitive. I should not get voltage from both meaning a possible bad coil??? do you think im moving in the right direction?
Thanks,
Denny

 

[Bt Doctur]

Re: on and off SPARK

A bad tach could mimic no spark.Remove the grey wire from the coil that goes to the harness not the grey wire that goes to the module.

 

[dgopetactical]

Re: on and off SPARK

ok I will do that. should I still be getting power on both pins on the coil with the key on?
thanks

 

[JustJason]

Re: on and off SPARK

yeah you will be getting power... its either 5 volts or 12... i forget wich.
either way....
if you found it rusted... it was probably tapping out on the reluctor and grounding out. Its a hall effect sensor and works on a magnetic field... even though there is power going to it, its probably not producing a magnetic field.
I'd replace the sensor (new ones are all encased in plastic so they will never rust) and the rotor/reluctor (comes as 1 piece)
Everyone i've ever seen rusted to beans has been bad/intermitent.

 

[dgopetactical]

Re: on and off SPARK

thank you for the above replys. i will replace the sensor. pull the grey wire(tach) from the coil and try it. I also read about removing the shift interupter wire from the coil what color is that wire and any info on that?
Thanks

 

[Chris1956]

Re: on and off SPARK

Trace the wire to the shift interrupter. It is only 3 feet away on the upper shift cable to lower shift cable connection.

 

[krisnowicki]

Re: on and off SPARK

You need mercruiser manual 1b on page four is the Tbolt test tree for spark. Just so you know they consider intermittent spark= no spark for the testing tree. Use and you will find your problem. If you dont have it or cant find it online pm me and I will email it to you.

 

[dgopetactical]

Re: on and off SPARK

A bad tach could mimic no spark.Remove the grey wire from the coil that goes to the harness not the grey wire that goes to the module.

Felling better today. I removed the grey (tach) wire from the coil.
Turned the key and VAROOOOM!!!!!!. runs good. now I need a tach. trying to fiigure out what the malfunction is and not having much luck. was thinking about getting one of thoes dash mounted ones if I cant figure out the current problem just need info on hookup. any ideas. I will let you know if I come up with something
thanks
Denny

 

[dgopetactical]

Re: on and off SPARK

I think we got it. I Found a short in the grey(tach) wire in the harness.. I fixed the short connected the grey wire back to the coil turned the key and varoom. and the tach works also.
Thanks for your help
Denny