Universal M-12 Glow Plug Solenoid not working

Apr 21, 2019
3
Pearson 32 Port Washington
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hello, I have Pearson 32 with a Universal M-12, not the original motor or wiring.

The glow plugs do not work when I press the glow plug button in the cockpit.
I have 12V at the “s” terminal on the solenoid when I press an hold the button
I have 12V on the always hot side of the solenoid coming from the starter
The fuel pump works when I press the glow plug button
The glow plugs are verified good because I jump the heavy 12V from one side to the other and the engine fires immediately when starting from cold. It did not start prior to jumping the solenoid and attempting to preheat the glow plugs by pressing the button.
I have an open circuit across the “s” and “i” terminals on the original solenoid, and I replaced the solenoid with one from Napa auto, GPR500.
Same exact symptom with the new solenoid except there is a closed circuit between “s” and “i” as I would expect.

I believe I have a ground issue with the solenoid as it doesn’t not click or is there 12V on the “i” terminal when pressing the preheat button.

The original solenoids mount ran down to the base of the solenoid, like a shelf if you will that the solenoid sat on and has the 4 rivets to the plastic housing.

The new solenoid mounts to the top of the solenoid and hangs, and is not electrically attached to the bottom of the solenoid.

I suspect the original solenoid gets its ground through the base and mount.

The original solenoid has no part # or manufacturer name.

Any suggestions?
 
May 20, 2016
3,014
Catalina 36 MK1 94 Everett, WA
What is the little silver box on the solenoid?? Glow plugs are ~12A each so a 30/60 could be used and cheaper than the starter solenoid you have now. If you really think bad ground - remove the thing clean where it bolts down and try again.
 
Apr 21, 2019
3
Pearson 32 Port Washington
Hi Stu, thanks for the reply and suggestions. I already jumped the new solenoid, and the engine starting after holding the after for about 10 seconds, which indicates to me the glow plugs are both working as designed. I see in your diagram a separate ground wire. I don't think I need it as the mounts are metal to metal on the engine, but its worth a shot.
 
Apr 21, 2019
3
Pearson 32 Port Washington
What is the little silver box on the solenoid?? Glow plugs are ~12A each so a 30/60 could be used and cheaper than the starter solenoid you have now. If you really think bad ground - remove the thing clean where it bolts down and try again.
Les, the little silver box is a 10A circuit breaker. I will check it again, as I assumed (yup) its closed because when I press the preheat button, the fuel pump clicks away and pressurizes the fuel system. Then again, it did that with the old solenoid, which I verified has an open circuit between the S and I terminals. That little box is something to reconsider jumping out as well this weekend. Thanks for making me re-think it.

Rob
 
Nov 10, 2012
22
S2 9.2 ST IGNAGE, MI
the solenoid should have 2 small terminals. One should come from the start switch and the other small terminals so should go to the engine block or the battery ground.