Idle Cutoff Solenoid Rebuild

[C6H12O6]

After a fresh rebuild of my 1974 Aisin carb, my Idle Cutoff Solenoid wasn't working. I could pump the gas on startup and get it to fire, but as soon as the gas the accelerator pump put in was burned off, the truck just died, just like it did when I forgot to plug the solenoid back in once.

Upon checking the solenoid, it was plugged in, but it wasn't making a click like it should when the key turns on. The solenoid looked a little cruddy, so I decided to pull it back off and give it the once over. I took a couple pics along the way, since I didn't see much in my quick search. Please post up to correct my mistakes if I make any.

 

[C6H12O6]

Here is a shot showing where I pulled the casing apart. There was just enough of a gap to get a small screwdriver in there and pry the cap off. If you look closely, you can see the hole in the outer cap and the small dimple in the base that it engages to hold the two pieces together.

 

[C6H12O6]

When separated, the rod, rod holder and spring come apart from each other and slide out of the base and cap. My rod was bent up, which was probably what kept it from opening up properly.

The rod assembly slides (spring side down) into the tube in the cap.

 

[C6H12O6]

If you carefully remove the o-ring and pry the washer-like piece out, you can remove the solenoid electromagnet. When you pass 12V through the solenoid, it creates a magnetic field that pulls the rod back into the solenoid. When the 12V is cut when the key turns off, the electromagnet turns off, the spring pushes the rod back out, and the rod blocks the gas flow in the idle circuit. Without this, the truck just keeps running.

 

[C6H12O6]

The wires should have little rubber grommets where they come through the exterior case of the solenoid. Mine were shot, so I replaced them with generic rubber grommets from a Home Depot variety pack.

 

[C6H12O6]

After cleaning the crud out, polishing the rod retainer metal piece with 2000-grit sandpaper and straightening the rod, I reassembled the solenoid and tested with 12V from the battery. You should see the rod pull back with 12V, as in the video.

 

[C6H12O6]

Here it is installed back on the carburetor. You can hear the click, telling you that the rod is properly opening the idle circuit when the key turns on. As you can see, I'm still using the jumper to get 12V straight from the battery, as I'm not getting 12V from the keyed wire. That's the next project, as using the jumper will make it run, but you must remove the jumper to kill the truck. Even with the key out, the running engine just keeps itself running.

 

[ToyotaMatt]

Every once in a while somebody Re-Invents "a" wheel



Great Tech @C6H12O6 !

& even better Videos to boot ..................

 

[cruiserboy14]

omg!!!! this is exactly what I needed!!!!!!! todays project is.......

 

[C6H12O6]

Good luck. Seriously, a zero banana job. Now, if only the wire for the solenoid was on the wiring diagram so I could figure out where it goes without crawling under the dash.

 

[swelltimes]

This is a great write-up. Thanks @C6H12O6!

 

[thebigredrocker]

Not sure if 74’s have the 4wd indicator.

......
If I remember correctly the idle solenoid connected to the same wire as the coil switched ignition wire (BY wire on + side of coil) However some say that is not a good idea due to the fact that if you get a short in the idle solenoid wire it can take out the ignition circuit which is NOT fused on older trucks! A better solution that I build into all my new harnesses for older trucks, is to use the 4WD light as the idle solenoid power source. I simply use a double bullet connector when I build a new harness and make up an idle solenoid wire to plug into that.

I can supply you with a small splitter adapter and a length of wire. You would unplug one side of the 4WD light, plug in the splitter adapter, plug the 4WD into one side of the splitter then plug the idle solenoid wire into the other and route it out to the idle solenoid. Th 4WD light is on a fused circuit.

 

[cbmontgo]

Wow. I think about how many OEM solenoids have been tossed in the trash all these years, while only needing minor TLC instead of replacement of a $ 125 part.

Great thread.

 

[C6H12O6]

Yeah, there really isn’t much going on in there. The only real deal breaker is the electromagnet. Even that would be easy to fix.

 

[cruiserboy14]

.... mine looked nothing like this....

 

[C6H12O6]

Bummer. I think most of the 2F carbs had a threaded solenoid, instead of the type shown here. I'm sure it's the same principle inside, if you can get it open. I don't have a later 2F carb, or I'd try to pull one apart and update the thread.

 

[cruiserboy14]

It’s ok, I have a 77 and it didn’t look as simple as yours. I apologize, I didn’t take a picture...

 

[emac]

aftermarket ones are only about $15

 

[cruiserboy14]

Oh! Well I guess I’m bugging my O’Reillys.

 

[C6H12O6]

Just for completeness, my wiring issue after the rebuild was due to a blown ignition fuse. I accidentally grounded the jumper wire clamp from the battery and the sparking wire touched the idle cutoff solenoid wire. Luckily, it seems like the 20A fuse did its job and took one for the team. New fuse and the solenoid works as it should—a pleasing little click when you turn the key on and a nice, steady idle after startup.