AUX MAG switch

[Jerry Morris]

One of my 300 hp 6BTA5.9 engines has trouble starting when warm. I’ve traced it down to the fuel shutoff solenoid. I’ve replaced the solenoid and it is good. Engine starts when cold, but after running a while and warming won’t restart. I’ve traced wires, cleaned connections and checked for tightness of connections. I can always get it to start by going down and “assisting” the fuel solenoid to retract. Hold down always works once running.
My question is, can the AUX MAG switch be going out due to heat? Or, is there a way to test it. I hate to just start replacing parts and hope to get lucky.

Thx

Jerry

Topic

[Tony Athens]

Make sure 100% of the “Monkey Motion” linkage on the solenoid & lever get plenty of lube on them so all is SMOOTH.. Be sloppy and work the linkage and then clean it up..

Tony

[Jerry Morris]

So far, so good

OK, I moved the ground wire from the solenoid directly to the mount on the engine case, and connected the original ground there as well.
I removed the old 3 plug connector from solenoid and harness and installed new spade connectors on the white pull in wire and the purple hold in wire. Cleaned and checked connectors on aux mag end and lubed and tightened. Checked resistance of pull in wire and it showed no resistance.
Cranked right up. Warmed up engines and let sit to heat soak and recranked ok.
Haven’t been able to take boat out for extended run yet.

[Jerry Morris]

Seems like low voltage

I’m out of town for several days so can’t get at it yet.
I did check the solenoid before installing it and it retracted when power was applied to white wire. I will switch the ground to the mounting tab on engine and am going to install new #12 wire and connectors from mag switch to solenoid. I felt it was a voltage drop problem but didn’t know what the aux mag switch did.
Will report back when I get back.

Thx

Jerry

[Tony Athens]

Jay,

OK, you read my post and came back with a darn good response.. So with that, I decided to go a tad deeper and try a start on a mini article on what applies here…. You are 1st in line to see if I have succeeded in trying to sort this out to you and all the others that may need help.. Be sure you study the pic..

Let me now how it goes..
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Time for a class in “Fuel Solenoids 101”..

1) Grab your old solenoid and get a 12V battery & some 12ga test leads —Go to your bench.. .. Cut the Black wire off the plug ( as close to the plug as possible) and install a GOOD 1/4″ Heavy duty ring terminal on the end.. This is now PERMENENT and IMO, you should do the same on the one on the engine.. This is the common ground for the TWO INTERNAL coils inside the solenoid and goes under the mounting bolt on the solenoid bracket when mounted to the engine–This makes for a SUPERIOR ground with less voltage/current drop.

2) Now, let’s LEARN your solenoid as to how it works..
1st, ground the black lead (12V NEG) .. 2nd, Put 12V POS to the RED lead—you’ll “see” a 1 amp spark when you do it, but that is all.. Now, with that leads connected, PUSH the solenoid in to the “HOLD” position.. This is what keeps you engine running and HOLDS the injection pump fuel lever in the RUN POSITION.. This runs off the engines IGN circuit.. The solenoid, in this mode uses about 12 watts of power and over a few hours will heat up to about 120-160F sitting on a bench overnight.. The solenoid will hold in this position until power is disconnected.. Undo a lead, a see what happens..

Now, let’s keep the GND connected and put power to the WHITE lead- WOW is what you will say as now that “coil” inside the solenoid in trying to use over 20 AMPS, and that is a BIG spark.. The solenoid will suck in and hold there until YOU break cranking power, and then go back to only the “IGN on” position which BREAKS that cranking position connection .. This is a very intermittent use “coil” and is only designed to stay energized while the engine is trying to start—very few to maybe 30 seconds at a time..

So now, YOU NEED to understand how the system works as explained above, and when you do, YOU will now understand what your issue is.. To me it is too simple to figure out..

Tony

[Jerry Morris]

Photos to clarify

Here are photos of my setup. The solenoid does not have any linkages to adjust. Strictly a retract, holdin and extend to shut the fuel off. I had one spare solenoid that I installed and it did not retract, so since it came with the boat and I couldn’t verify that it worked properly, I replaced it with a new one. Same results. Won’t retract on hot start, but holds in run (retracted) position until ignition switch off. I can just barely assist it to retract and it works.
The second photo is what I believe to be called the AUX MAG switch, located just under the starter. The large white wire coming off the top stud goes to the center prong on the solenoid switch, which according to my schematic is the retract wire on the solenoid.
The engine is a 6BTA 5.9 M2
S/N 60237043

Hope these help..
Thx
It appears the photo of the switch loaded upside down. The metal bracket should appear on top.

[Tony Athens]

Pictures, pictures and more pictures so “we can see” exactly what you need sorted out and what you have in the engine room… All must be clear and in-focus..

No other way.. Heck, I don’t even know what engine you have..We’re really good here, but no crystal balls..

Tony

[glenn111]

Not sure what the Au Mag switch is.

Just changed my fuel solenoid. Last one burnt up in the coil area and fried (smoke) the connectors also (male and female). Ordered the solenoid from internet ($ 100) and exact connectors also. To get it to work properly, both pull and hold, had to “play around/adjust” the adjustment linkage on the solenoid. At one point, would pull and hold but not release when shut key off. So maybe, play around with the linkage adjustment on the solenoid to “fit” your situation.

[Author]

Replies