ignition voltage drop

[joseph1980]

Hi guys, i've got a 2000 reinell with a 3.0 liter mercruiser and the est ignition system. I noticed while trying to start it today that i was gettin no fire to the plugs. after looking at several things i found that the purple hot wire goin to the coil showed 12.2 volts with the switch on and while cranking the voltage dropped to like 2 volts if i remember correctly. i assume this is why i am not getting a spark. any ideas what may cause the voltage to drop like this? i wired the safety kill switch together so i know thats no it...

joseph

 

[Bondo]

Re: ignition voltage drop

Ayuh,.... Your battery is Weak,... recharge it, or if that don't work,...
Replace it...

 

[joseph1980]

Re: ignition voltage drop

these reading where after cranking it multiple times....so would that have an effect on the readings? I guess i don't understand how a battery not being fully charge would cause a drop in voltage like that...?

 

[Bondo]

Re: ignition voltage drop

Ayuh,... If the Battery is Beat, it won't have the reserve amperage to maintain the Voltage when called upon...
That's Why a Battery "Load Test" will actually tell you the overall condition of said Battery...

 

[joseph1980]

Re: ignition voltage drop

i tried another battery that i use in my daily driver. battery showed 12.2 volts and showed 12.2 volts at coil wire with switch on...while cranking voltage dropped to 0.

 

[Don S]

Re: ignition voltage drop

You may have a loose or corroded terminal in the wiring someplace. Check at the main round 10 pin connector, plus there are several soldered splices.
Since it is a 2000 model, might try disconnecting the shift interrupt switch. That new style switch I've had problems with before. Just disconnect the purple wire from the switch and see if your voltage comes up.

 

[FreeBeeTony]

Re: ignition voltage drop

Maybe the gnd???

 

[joseph1980]

Re: ignition voltage drop

i've tried it with the shift interrupt switch disconnected and that made no difference. i've checked that the all the obvious grounds i could see where tight, i may go ahead and disconnect them to make sure that they are clean too. would an alternator issue possibly cause this? i saw that it used the same purple wire. i went to have it tested at auto zone and advance and neither could seem to figure out how to hook it up to test it... all the purple wires have 12 volts to them (the alternator, choke, shift interrupt switch and the coil).

 

[Don S]

Re: ignition voltage drop

Disconnect the purple wire off the alternator and give it a try. It won't hurt anything, but your alternator won't charge when you do start it.

I trust that when you are checking this voltage at the purple wire going to the coil, thaat the wire is not plugged into the coil. Is that correct?
Also disconnect your tachometer, it could be shorted out causing the problem.

 

[joseph1980]

Re: ignition voltage drop

umm no with the switch in the on position and the coil wire connected to the coil it shows 12 volts, then upon cranking that it shows 0 volts...

 

[Don S]

Re: ignition voltage drop

Disconnect that plug from the coil and crank it while checking the voltage on the plug, and see if the voltage drops.

 

[joseph1980]

Re: ignition voltage drop

i disconnected the plug from the coil and came up with similar result 12 volts with key on fell to 0.21 volts while cranking.

 

[Don S]

Re: ignition voltage drop

Not sure what I was thinking, Start at the ignition switch, on the purple wire and see what you have on the purple wire. Matter of fact, after you test it with the purple wire connected, if you show the same thing disconnect the purple wire and test. If same thing. Replace the ignition switch. Also check the main red wire on the switch.

 

[JustJason]

Re: ignition voltage drop

how to do a voltage drop test.

http://rds.yahoo.com/_ylt=A0geu6v1v...com/find-sales/download/asset/2418158_a_w.pdf

 

[joseph1980]

Re: ignition voltage drop

wow it ended up being a $9 dollar ignition switch! thanks everyone for the assistance!!

 

[Don S]

Re: ignition voltage drop

After I went back and re-read the original post, I realize you just bypassed the kill switch, but you didn't check to see if you had power before or after the switch.

Kind of the hazards of not being there.

Glad you found the problem.

 

[rodbolt]

Re: ignition voltage drop

dang
I wish DonS would fix his crystal ball.
maybe ill have to show up on his door step soon .