Aisin carburetor idle circuit routing (1 Viewer)

[Scotty2]

I did a quick check of my Stop Solenoid which tested ok on the workbench. I’m getting the 12vdc signal from the ignition switch as per design. But the solenoid is working only intermittently. That is, it pulls in ok, but doesn’t release consistently. I’m gonna pull it apart and see if I can clean and polish the innards to improve its operation.

If no joy, who sells these little gizmos? I looked at SOR and CCOT but didn’t see one for sale…

 

[Grayscale]

I'd use carb chem-dip, as it is probably varnish that is making it stick?

 

[Scotty2]

Have we ruled out your fuel cut-off solenoid yet?

Pighead, I returned to the stop solenoid today and it worked sluggishly and intermittently. So, I disassembled the solenoid and cleaned the varnish off every thing with alcohol and q-tips. After reassembly, it works great. Gonna crank the beast up tomorrow to see if this helped.

So I don’t lose the big picture here, the Idle Stop Solenoid energizes when the ignition is On, causing the plunger to retract, enabling Idle fuel flow. Once the ignition is Off, the plunger spring pushes it back into a valve seat somewhere shutting off idle fuel flow. Am I close?

 

[Pighead]

Am I close?

Yup, that's it

 

[Scotty2]

Yup, that's it

I am happy to announce that the patient is out of the hospital!!!

The Idle Stop Solenoid was The Problem. It was intermiitantly working, so I disassembled it, cleaned all the innards, and put it back together. Now it clicks very positively to its positions.

The effect was immediate. The engine is idling very smoothly at 650, with the timing at The BB, and vacuum at 17.5 in hg.

I’m really thankful for all of you who spent hours helping me through this. I really appreciate it!!

Not only did you help me fix this solenoid, but installing thread repair Helicoils for the carb studs, also getting the carb rods into the correct linkage holes, adjusting the IMS and ISS and the Fast Idle Screw!! And just better understanding of how the Idle Circuit of a carb works.

Probably some other stuff too!!

Thanks much!!!

Scotty2

 

[charliemeyer007]

Man over machine! My dad said a smart guy invented the TV, but a smarter guy invented the off switch. Well done.

 

[Scotty2]

Man over machine! My dad said a smart guy invented the TV, but a smarter guy invented the off switch. Well done.

Thank you sir! It was a war of attrition… I just refused to give up, though I almost did. Every time I was stumped the Panel of Experts weighed in to give me more ideas. Thanks to all!!

 

[Scotty2]

It was 33 degrees here this am, but my FJ40 started right up with the aid of the choke. After it warmed up I shut off the choke and it ran at 900 rpm, 21 in Hg, at an unknown timing.

I rotated the dizzy CCW to achieve the max vacuum of 23 in Hg. I backed it off to 22 in Hg at 1000 rpm.

I locked down the dizzy and took it for a drive. All the hesitation and bogging down was GONE!! Having the timing at “the BB” (aka 7 degrees) was not good!

So next I decided to try the Lean-Drop Method of adjusting the carburetor IMS and ISS. Out of curiosity, I ran the IMS screw all the way in, and the engine died. Hoorah, I am running strictly on the idle circuit of the carb. Then after trying the Lean-Drop Method I ended up at 650 rpm and 18 in Hg.

With a little more nudging on the dizzy and tweaking the ISS, I ended up at 690 rpm and 21 In Hg.

I’m finally content with it!! Haha

But as you might have guessed, I have more questions:

1. Remembering my sordid past of monkeying around with Chevy and VW carburetors, I remember that as the engines warmed up, there was a thermostatically controlled multi-step plate that rotated under the Throttle Screw. So if you slightly tapped the gas pedal, the idle would progressively dropped.

Anyhow, being a cold day today in N Florida, I witnessed the FJ40 do the same thing. But I don’t see the familiar multi-step plate. How does Aisan do it? I think mine needs some lube or polish. It’s not consistent.

2. Why in the world would the Toyota design team place a BB at 7 degrees when everyone I’ve heard or read says that 7 is not even close?

 

[Grayscale]

But as you might have guessed, I have more questions:

1. Remembering my sordid past of monkeying around with Chevy and VW carburetors, I remember that as the engines warmed up, there was a thermostatically controlled multi-step plate that rotated under the Throttle Screw. So if you slightly tapped the gas pedal, the idle would progressively dropped.

Anyhow, being a cold day today in N Florida, I witnessed the FJ40 do the same thing. But I don’t see the familiar multi-step plate. How does Aisan do it? I think mine needs some lube or polish. It’s not consistent.

2. Why in the world would the Toyota design team place a BB at 7 degrees when everyone I’ve heard or read says that 7 is not even close?

Mine is at 7 deg. It runs great in warm weather, no dieseling, no ping, 88 octane at 7,000' altitude.

The USA-Aisan had that throttle positioner / choke-breaker diaphragm that we talked about earlier. You carb has had that deleted - green arrow. The multi-step plate that you speak of is akin to the single-step, screw, and the throttle arm. Some carbs require you to set this mechanism by depressing the throttle. I can't tell if my stock carb is like that because I had the throttle positioner backed-off, as I had plenty of fast-idle with just pulling the choke knob.