can a bad tac kill the ignition?

[ussoldier_1984]

I have a ignition issue im sure most of you are familiar with. I have posted questions about it on here. today I was making sure all electronics were working testing blower, bilge lights. all was good, but I noticed that my tack was reading 300rpms then jumped down to about 50rpms (engine was not running) could a bad tack cause the ignition to not spark strong enough? or ground out the coil? why would my tack be reading a signal of 50 rpms when the engine is not running. my outdrive is off (doing water impeller service) can I disconnect tac and try to start engine with outdrive off? without hurting anything?

 

[ussoldier_1984]

Re: can a bad tac kill the ignition?

If you didnt notice im talking about my sig boat 1995 maxum 1800SR 4.3lx with thunderbolt IV ignition

 

[bruceb58]

Re: can a bad tac kill the ignition?

Your tach jumping around with the engine off is possible. It is also possibele a bad tach can kill your ignition. No problem running without the tach as a test.

 

[ussoldier_1984]

Re: can a bad tac kill the ignition?

but is it safe to try to start with the full outdrive off? i dont want to hurt anything, and where should I disconnect the tack at the coil or at the tac?

 

[HT32BSX115]

Re: can a bad tac kill the ignition?

Howdy,


The TACH *could* cause you ignition problems if it was shorted internally, connected incorrectly, etc..... On most electronic ignitions systems, it's just a (electrical) pulse counter.

Yes you can usually just disconnect it and run the engine (you just won't know what RPM the engine is turning) That'll be a good way to determine if it's causing a problem......


They frequently read wrong too and can be as much as 500 RPM off at the higher RPM's..........really screws up prop selection (reading WOT RPM) unless you know they're accurate.

but is it safe to try to start with the full outdrive off? i dont want to hurt anything, and where should I disconnect the tack at the coil or at the tac?

Yes. just make sure you have a water supply (to run very long) into the T-stat housing where the hose comes from the drive raw water pump.....

Regards,


Rick

 

[Don S]

Re: can a bad tac kill the ignition?

It won't hurt a thing to run the engine with the drive off. Don't run it more than 15 seconds or so, or you will burn the exhust hoses and flappers, but it will be enough to see if it runs.

 

[ussoldier_1984]

Re: can a bad tac kill the ignition?

but is it safe to start the engine with the outdrive off?\

edit sorry didnt see your post you answered right when i was typing this

 

[ussoldier_1984]

Re: can a bad tac kill the ignition?

no luck disconnected tac at the coil and no signs of life thanks for the input guys!!

 

[Don S]

Re: can a bad tac kill the ignition?

Did you replace the sensor in the distributor ????? In your other thread on the subject http://forums.iboats.com/showthread.php?t=463927 it was found you had a bad sensor. Unhooking a tach is not going to fix the sensor.