Troubleshooting Secondary Slow Cut Valve Modification on Aisin 2F Carb (1 Viewer)

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Hey Folks,

I'm looking for suggestions on how I might go about diagnosing whether or not the modification I did to the Secondary Slow Cut Valve (see image below) is working correctly.

This is on a OEM Aisin Carb (PN 21100-61141) from a 2F 12/1981 FJ60 USA.

After having successfully rebuilt the carb several months ago, the secondary slow cut valve began leaking gasoline through the valve to outside the assembly.
Following MUD modification guidelines, I removed the valve assembly, pulled the valve from the housing, tapped the housing and threaded in and JB welded a bolt.
The modification allows for gas to be drawn into the second barrel by vac alone (vac created by the position of the butterfly - #13 in diagram below - on the secondary throttle shaft), no longer requiring the the mechanical opening of the secondary valve - #11 in diagram below - to allow gasoline to enter that circuit. (see diagram below)

I am wondering if after having done the modification, whether excess gasoline is entering the second barrel and causing performance issues...and if so, is there a way I can test to rule out whether or not is or isn't working correctly...because if it isn't, then I would have to get another, properly working Valve assembly and they are rather pricey (PN 21346-61140)...

The symptoms I have noticed since the modification are poor gas mileage (went from 12 city 15 highway before the mod to half that after the mod) and sluggishness under acceleration.

Any suggestions on how to rule out poor metering or fuel 'leaking' through the carb (especially this secondary circuit) would be helpful.

Thx.





I have noticed that the fuel level in the fuel bowl goes down overnight, but I attribute that to evaporation? The fuel pump is new (fuel filter fills about 1/4 full at idle)...no gas leaking from pump into crankcase...

All the Emissions systems/components are working correctly (new EGR Valve and Modulator), new vac lines, no vac leaks (excellent vac at idle 21 inHg), ICS working correctly.

Ignition Vac advance is working correctly (although I haven't ruled out weak springs as a cause for these symptoms, either, just can't find new OEM or comparable springs and don't want to risk messing around with finding suitable replacements until I rule out carb related stuff).
Base timing is set at 7* BTDC.


secondary slow cut valve.jpg


Carb Cirucits 2f Aisin FJ60_secondary slow cut valve circuit.JPG.jpg
 
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Is it possible to close the secondary throttle plate a bit , so that the 'idle' port is above the throttle plate.
 
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Is it possible to close the secondary throttle plate a bit , so that the 'idle' port is above the throttle plate.
Thx unkklwedy. My understanding on how that works is that there is still (even after having removed the Secondary Slow Cut Valve) a mechanical actuation on the secondary throttle shaft itself so that at idle, the butterfly valve on the secondary throttle shaft is below that secondary slow cut circuit port (#11 in image above) in the wall of the barrel, which therefor doesn't see any vac...but once the secondary throttle shaft is kicked 'open' at wide open throttle (WOT), then vac takes over and starts to draw fuel in through that circuit.

So, at WOT, the both the primary and secondary shaft have been mechanically 'kicked open'. And in the secondary barrel, that mechanical actuation is enough to have moved the butteryfly valve (#13 in image above) on the secondary throttle shaft above the secondary slow cut circuit port (#11 in image above) in the wall of the barrel, so that that port sees vac and draws in fuel.

The difference the mod makes, as far as I understand, is that fuel is allowed to pass freely up to that port in the wall of the secondary barrel at all times, instead of being only allowed to pas there when the valve has been lifted (timed in coordinatation with the mechanical actuation of the secondary throttle shaft at WOT).

So the assumption of the modification is that fuel will still only be drawn from that port when there is vac (at WOT when the position of that butterfly valve is positioned above the port) and when there is no vac (at idle), then no fuel is drawn into the secondary barrel.

I'm wondering if either fuel is being drawn into the secondary barrel when it shouldn't be or if not enough fuel is being drawn in, because after the modification I did not adjust the actuation of the secondary throttle shaft.

So if excess fuel is 'leaking' into the secondary, that might explain my symptoms or if I'm getting fuel starvation at WOT that might also explain my symptoms???
 
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Is it possible to close the secondary throttle plate a bit , so that the 'idle' port is above the throttle plate.

Or maybe to more directly address your suggestion, I haven't yet made any adjustments to the linkages to the secondary throttle shaft in order to try and change the relative position of the secondary throttle plate.

At carb rebuild, the current settings of those linkages spec'd out OK so that the throttle plate opened to spec when kicked out mechanically at WOT.

And at idle, the secondary throttle plate was shut.
 
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Secondary Fuel Cut Valve 21346-61140 has been NLA for a VLT

(as if that information is worth a rat's ass)
 
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Secondary Fuel Cut Valve 21346-61140 has been NLA for a VLT

(as if that information is worth a rat's ass)
Hmm...looks like if I will need this, then it'll have to be a used one...
Thanks for the info, OS!
 
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Alright, I went back and searched through MUD to see if I could find info on how these slow circuits should be working, and this is another pass at trying to understand...

Secondary Slow Circuit (#2)

Before mod
At idle, the Secondary Slow Cut Valve is closed, thus preventing fuel from flowing through the 2nd Slow circuit to the port in the wall of the 2nd barrel.
Past ~50% throttle, the throttle linkage kicks open both the 2nd Throttle Plate (creating vac at the 2nd Slow circuit port in the wall of the 2nd barrel) and opens the 2nd Slow Cut Valve. Now fuel can be drawn in, by vac, into the 2nd barrel through the 2nd Slow circuit.
Without fuel flowing through the 2nd Slow circuit, there will be a stumble as the secondary opens as a result of fuel starvation in transition.
At WOT, I would expect fuel to continue to flow through the 2nd Slow circuit even as fuel is also now being delivered through the 2nd Main circuit...

After mod
After the mod, the 2nd Slow circuit is left open at all times, no longer requiring mechanical actuation to open the 2nd Slow Cut Valve in order for fuel to be drawn through to the 2nd barrel.
Now, without the 2nd Slow Cut Valve, fuel should only be drawn through the 2nd Slow circuit when the 2nd Slow port is uncovered (i.e. the 2nd Throttle Plate is open...creating vac at that port).
If, at idle, the 2nd Throttle Plate is not completely closed, fuel can drip into the 2nd barrel since there is a vac being generated at that port and the 2nd Slow circuit has been left open (2nd Slow Cut Valve has been removed).
So, in order to prevent fuel leaking into the 2nd barrel after the mod, the 2nd Throttle Plate must be completely closed, covering the port so that vac is not created that would draw fuel from the 2nd Slow circuit at idle.

To check for a fuel leak inside carb:
"Verify that the ICS is actually cutting of fuel. Unplug the connector at carb w/ engine idling normally. Engine should shut off. If not, the ICS is not shutting."
Jim C.
"Another possible fuel leak is the secondary barrel. If it does not shut & seal totally, it can suck fuel out of the secondary slow port."
Jim C.
https://forum.ih8mud.com/threads/cruisers-popping.127201/#post-1686199



Primary Slow Circuit (#16)

At idle, the 1st Throttle Plate (#14) must be only partially closed over the throat of the 1st barrel, allowing vac on the 1st Slow circuit port in the walls of the throat of the carb (#15) to draw in fuel.
So the ICS (Idle Control Solenoid #7) must be open at idle...closed under throttle (when the primary main circuit (#17) takes over)?

Here are links to the MUD posts I got the above information from:
https://forum.ih8mud.com/threads/carb-leak.130815/
https://forum.ih8mud.com/threads/86fj60-leaking-fuel-at-carb.106686/#post-3564223
https://forum.ih8mud.com/threads/cruisers-popping.127201/#post-1686199
https://forum.ih8mud.com/threads/82-fj60-looses-power-going-up-hills.52031/#post-582547

Carb Cirucits 2f Aisin FJ60.JPG
 
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All the Emissions systems/components are working correctly (new EGR Valve and Modulator), new vac lines, no vac leaks (excellent vac at idle 21 inHg), ICS working correctly.

BTW.. where on earth did you find a new EGR valve? ?? ??? ????. New ones went the way of the dodo a LTA

And yes, fuel disappearing from the float bowl overnight is not uncommon.
 
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BTW.. where on earth did you find a new EGR valve? ?? ??? ????. New ones went the way of the dodo a LTA
I can't remember. I bought it online maybe a year and 1/2 or two years ago (when I made the decision to not go the desmog route and committed to solving all the stock emissions issues) and they wouldn't let me return it so I installed it...

It was from a Cruiser shop...like Cool Cruisers....or Cruiser something or other...

Maybe here?:
http://coolfj40.stores.yahoo.net/egrvalve.html

...NLA...
 
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The primary throttle plate ain't closed at idle, it's open just alittle bit to let in some air. At idle the idle port should be right next to edge of throttle plate. Right above the primary idle port there is a transition slot(may 1/8 inch tall).

I still think it's possible to completely close secondary throttle plate( by bending link). The procedure is similar to adjusting throttle plate on fuel injection systems, Throttle plate just barely bumps into bore at idle( and a separate idle air motor provides idle air path.

If that don't werk I'll give $10 for FJ-60 parts buggy.
 
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Looking through the 2F FSM last night on how to set the Throttle Plate Positions...

...and I discovered that I was supposed to (but didn't) replace the gasket (I think it is a crush washer) on the vac passage bolt (the hollow one on the bottom that holds the two carb and insulator plates together). I just reused the gasket that was on there...

Any chance this might also be causing the problem, too? Would this mean that I might have an vac leak internal to the carb?

Anyone know if this gasket is standard in the Hygrade carburetor repair kit (791BS)? If not, suggestions on which gasket/where to find?

Thx.

Carb _Vac Passage Bolt_2F FSM.jpg
 
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The primary throttle plate ain't closed at idle, it's open just alittle bit to let in some air. At idle the idle port should be right next to edge of throttle plate. Right above the primary idle port there is a transition slot(may 1/8 inch tall).

I still think it's possible to completely close secondary throttle plate( by bending link). The procedure is similar to adjusting throttle plate on fuel injection systems, Throttle plate just barely bumps into bore at idle( and a separate idle air motor provides idle air path.

If that don't werk I'll give $10 for FJ-60 parts buggy.

OK, unklwedy, I'm becoming a believer...thanks again for the help...

Time and weather dependent, I'm going to take a look at the position of those throttle plates...gotta cross setting the valves off the list first...

...here's what I ran across in the 2F FSM on setting the position of those throttle plates:

and a MUD link on finding/making a gauge (SST 09240-00014) for measuring throttle plate angle:
https://forum.ih8mud.com/threads/wtb-carb-gauge-set-special-service-tools.757407/

Carb Adjustment_Primary Throttle Vavle_2F FSM.jpg


Carb Adjustment_Secondary Throttle Vavle_2F FSM.jpg


Carb Adjustment_Secondary Touch Angle_2F FSM.jpg


Carb Adjustment_Kick-Up_2F FSM.jpg
 
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I was never able to find the SST Gauge set for the carb adjustments on the 75 Carb I had. I ended up making two-one for the secondary kick-up and one for the choke.
The secondary spec was for the plate to be open ~25 degrees from the barrel at full primary opening.
I will get a pic of the brass gauge I made in the next day or so.

fuel sys adjustment fast idle.jpg
 
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Home made gauge for 75-78 Aisan carb secondary kick, plus gauge for choke(btw-the secondary also is opened ~2 mm-using a pin gauge(a common ohm meter test lead connection is just about that size)

IMG_1620.JPG


IMG_1621.JPG
 
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Home made gauge for 75-78 Aisan carb secondary kick, plus gauge for choke(btw-the secondary also is opened ~2 mm-using a pin gauge(a common ohm meter test lead connection is just about that size)
Great! Thanks for posting that up sggoat!

I do have a protractor (not a fancy one like that), but I should be able to mock up some gauges (as per FSM specs)...I might go with either hard plastic or cardboard...whatever I can find that holds a good edge and is easy to cut...

Cheers!
 
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I actually didn't use that one to make the gauges--it was too complicated-and was hard to mark the stock, but it did show the angles a little better than my Granddaughter's protractor that I used.
 
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Adjusted the valves 'cold' using the instructions from this thread:

https://forum.ih8mud.com/threads/fj60-valve-adjustment.489587/

The valve adjustment increased the performance some...took some of the stumble out of the acceleration...still not sure if it had an effect on increasing MPG back to normal, tho.

Pulling the carb is still on the to-do list but the check list for what to check with the carb off is growing...
 

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