As some of you may remember, my generator works, except that the shutdown solenoid is broken. It would run great, but had to be stopped by hand (shutting down the injector pump). Which was not nice since safety shutdowns did not have a chance to work.
The price of the replacement solenoid from Onan was $390, which nearly gave me a heart attack.
I bought a different solenoid from FW Murphy for $44 and received it today. Right away I noted that the return spring was too weak and that there was too much unnecessary pull depth/travel. I decided to exchange some depth for strength and tried to put in the spring from the old solenoid, and to pull the rod a little bit. FWMurphy solenoid had an ability to attach a threaded rod to the back to arrest excess forward travel. The spring from the old solenoid was too small diameter, so I had to widen it, using pliers judiciously.
All solenoids have greater pull strength if the rod is partially pushed in, that's why exchanging depth for strength works.
The spring also had to be clipped a little bit because the solenoid would not pull in all the way due to stopping action of the fully compressed spring.
Fortunately, in the end, it worked out: just the right amount of travel, just the right pushing force etc. I need to make a little fixture to adapt the mounting holes in the new solenoid, to the holes in the engine housing, but it is no big deal and I will do that tomorrow. I am quite hopeful, as it stands. For fastening, I will use Nylocks throughout.
Unlike the onan solenoid which has only two terminals, and internal disconnect for the heavy pull in coil, the FW Murphy solenoid has three terminals, so that there are separate sources of current for the pull in vs. the hold coil. Supposedly, the pull in coil attaches to the starter, and the hold coil attaches to the wires that were used for the solenoid originally.
I do not like this because the pull in coil needs to work for barely a second, whereas cranking will go on for seconds, possibly overheating the solenoid. I will think about what to do with it. It is workable though. I will place an inline marine switch on the wire to the pull in cord, so that, when prolonged (relatively to the burn up time of the solenoid) cranking is required, the solenoid would not overheat and burn.
Or, alternatively, I may add a push button switch to momentarily engage the solenoid while the engine cranks.i