the phantom primer solenoid

[johnyrude200]

OK so I’m missing something obvious here.

Working on a typical OMC 25hp mid 80’s motor. Primer solenoid is showing full voltage, but not activating. This solenoid is mounted to the lower cowel via a SS bracket, ground wire from the solenoid screwed into the mounting screw, hot lead (purple) comes from the key switch.

Well, when I run jumpers directly from the hot lead (purple) and ground the solenoid to any part of the motor, the solenoid works via the key switch.

As soon as I mount the solenoid, it will not work but show voltage through the SS mounting bracket. So there is high resistance somewhere in this bracket? I haven’t screwed the ground directly to the block yet, but was planning too. I’ve run my multimeter hot from the bracket and the multimeter ground to the motor block and showed proper voltage, but the solenoid isn’t activating. Show it gets power when mounted but won’t work, but when off the bracket works just fine. Obviously the bracket is the culprit….but trying to understand what I’m missing here?

I thought it was a bad key switch on my portable testing remote key switch harness, but after switching the key switch realized this wasn’t the root of the problem.

3 hours into screwing around, I find myself on here to listen to wiser minds.

[PugetSoundBoater]

As it seems the problem centers itself around the solenoid ground wire , have you inspected that ground wire VERY closely for a break in the wiring and where the wire enters the terminal to ground. Since you live near the salt chuck, there could also be some internal wiring corrosion causing resistance.
Another place to look for corrosion or a break is where the ground wire enters the solenoid. Do you have another solenoid to swap and see if it solves your problem. It could also be that the 30 year old solenoid itself is well on its way to failure .
Check the ground wire from the cowl to the midsection if there is one, and the ground wire from the powerhead to the lower cowl.
Check to see if the threaded hole in the cowl under the solenoid mount is corroded and the same with the related hold down bolt. Check the complete ground circuit path.

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

[billw]

That was a lot to read and I didn’t have either eye glasses or coffee yet; so forgive me if I missed something. But it sounds to me like your lower cowl is not grounded to the engine block. It is, after all, rubber-isolated. There must be a bonding wire between the block and cowl that is missing or broken….

Long live American manufacturing!

[frankr]

quote BillW:

That was a lot to read and I didn’t have either eye glasses or coffee yet; so forgive me if I missed something. But it sounds to me like your lower cowl is not grounded to the engine block. It is, after all, rubber-isolated. There must be a bonding wire between the block and cowl that is missing or broken….

Couldn’t have said it better myself. Check the cowl ground. OR, You did mention a ground wire to the block not connected.

[johnyrude200]

There is a grounding wire from block to ground, and Ive tried three different solenoids. Seems to be a bad ground; if the solenoid isnt on the bracket it works.

Im going to ground it to the block directly and be done with it and will report back. Oddball situation that I dont have time to waste on this time of the year!!!!

[johnyrude200]

So the problem was the grounding strap had internal rot. I knew it was something simple!

The moral of the story is, mental fatigue after a 12 hour day will make small obvious problems seem bigger than they are!

[fleetwin]

Absolutely….The more time I spend on something, the more confused I get….The simple answer usually comes to me at about 0300 while I am trying to sleep….

[Author]

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