Fuji 21100-61012 DeSmog Carb vs OEM FJ60 Carb - Fuel Cut Solenoid (ICS) Analysis/Questions (1 Viewer)

CruiserWil

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This system has been discussed before, but I want to delve deeper with this thread. Fair warning, it goes a bit out in the weeds...

I'm about to install a CityRacer/Fuji desmog carb (CR/Fuji) on my desmogged (still have Decel Fuel Cut, PCV, Distr Vent, & EVAP) '87 FJ60. Could keep the HIC/HAI systems if I want to. The CR/Fuji carb has only the one vacuum advance port. It's a pretty straight-forward install, except for the Fuel Cut Solenoid (FCS). I'm new to TLCs, but have dealt with stuff like this for decades. Looks to me like the CR/Fuji carb with 1-wire FCS to be installed on my truck cannot correctly perform the Decel Fuel Cut system job intended by the origional OEM 2-wire FCS/carb setup in an OEM FJ60 truck.

The OEM FCS system consists of a Fuel Cut Port, FCS, Vacuum Switch (VS), computer, and associated wiring & plumbing (see Components Diagram). I'd like to keep my truck from popping and banging on high-rpm throttle back-off, but don't see how it can be replicated with a 1-wire FCS setup. It's my understanding that's the only thing the FCS is meant to do--stop popping & banging in the exhaust during high-rpm deceleration (see Operation Table). It has nothing to do with engine idle when functioning normally. Problems with it could affect engine at idle or other revs if the FCS cuts the Slow Circuit when it shouldn't.

First, there is no Fuel Cut Port on a CR/Fuji carb to correctly drive the FJ60 VS. Trying to 'T' off the CR/Fuji Vacuum Advance Port will drive the VS in a way exactly opposite to how it should be driven by an OEM carb Fuel Cut Port. An Advance Port is low vacuum at idle, increasing vacuum as throttle butterfly opens; a Fuel Cut Port is high vacuum at idle, decreasing vacuum as throttle butterfly opens. A direct comparison of these two ports can be made by reviewing the bottom diagram on pg. 3-3 of the really excellent 2F Emissions FSM. The 2-wire FCS is switched on & off by the OEM 60 computer, which needs accurate input information from a correctly-ported VS and Engine RPM to operate nominally.

Second, the fact that the CR/Fuji FCS is a one-wire solenoid (grounded through carb body) cuts off the ability of an FJ60 computer to control the FCS, even if a correct Fuel Cut Port was available for the VS.

In an OEM 2-wire FJ60-controlled FCS system, one wire is switched 12v, the other is ground--but through the computer, then through the vacuum switch to ground (see FJ/BJ 60 Factory Wiring Diagram & 2F Decel System Diagram). This allows the computer to keep the OEM carb Slow Circuit open most of the time, only closing during higher (>1,800) revs, high vacuum deceleration (see Table). I.e., it cures the popping (afterburning) & banging in the exhaust only on the overrun. Nice to have.

So hopefully we can deal with the second problem by swapping in an origional OEM FJ60 2-wire FCS to the CR/Fuji carb, with a regular OEM 2-wire FCS hookup to the truck. If the 2-wire FCS Swap works, that leaves the first problem of correctly porting the VS. Looking for ideas on that from this very capable Forum. Where do you CR/Fuji folks port your VS? To the aircleaner, to the gas filter? Other?

Using the Gas Filter fitting might partially work, as it is higher vacuum at idle, decreasing vacuum as throttle butterfly opens, high vacuum on overrun. Though it probably won't be as sensitive and quick-responding as a proper OEM carb Fuel Cut Port. On the overrun, venting VS to ambient (air cleaner) leaves the Slow Circuit open (VS is always on, opening slow circuit, but with the OEM setup rpm is a factor here too). So the symptom of this scenario would be exhaust banging/popping on overrun? But what would the computer do under a high rpm, no vacuum to VS (remember, VS is now vented to ambient) scenario? Really in the weeds here, beginning to smell smoke....;}

Another proposal is to have the 1-wire FCS connected to switched 12v, which means the CR/Fuji carb will function normally, though you'll have afterburning in the exhaust on overrun. Thinking about it, folks who report having to run their CR/Fuji carb with the choke on a bit all the time would have to do so if their FCS isn't energized (Slow Circuit is closed), which leans the carb a bit through the rev range.

So, my first try will be with the CR/Fuji carb with a 2-wire FCS (if it swaps) hooked up normally, but with VS vacuum line going to Gas Filter manifold fitting (due to lack of a Fuel Cut Port). The CR/Fuji Advance Port (the only port) will be 'T'ed to the distributor advance diaphragm and the EVAP VCV through the existing single BVSV. The remaining emissions systems don't require carb vacuum ports.

Can't experiment until I solve a 2-minute unbelievably, horrendously loud steady whistling sound during initial warmup of my truck. Plus I just work slowly, I'm retired :}. Constructive criticism/error analysis most welcome.


FCS Components Placement Diagram.jpg


1983 FJ-BJ 60 Series Factory Wiring Diagram.jpg


2F Decel System Diagram.jpg


FCS Operation Table.jpg
 

OSS

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I've run the 2F without the deceleration fuel cut system active and it's not an issue. Engine gurgles a little more during engine braking but it doesn't backfire. It's nice to have if you've got a functioning vacuum switch and computer but it's definitely not a game changer. Just a nuanced improvement.
It's mostly there to improve emissions.

So the next issue Is the fuel cut system on shut down to prevent dieseling. This IS important otherwise turning off the engine is a sputtering banging croaking affair as it gasps its last breathe before conking out.

The fuel cut solenoid doesn't require a vacuum source to turn on & off — only a switched 12V source. For just engine stopping use, it can be wired through the Engine fused circuit at the fuse panel. Then when the key is turned ON, it will energize and open the fuel passageway, and when the key is OFF, it will be de-energized and shut off fuel to the carb for a civilized shut down. The emissions computer isn't needed for Shutdown functionality.

As for a single wire or double wire solenoid, that's only a grounding issue. The non original FCS grounds through its threads into the carb body so it needs a switched 12V+ source, while the original 2 wire solenoid has its own dedicated ground wire which connected to the computer circuit.

If I were in your boots, I'd forgoe using the deceleration fuel cut system for now and drive the car without it and see how you like it. You might not notice it's missing.
But definitely hook up the engine shut off fuel cut system — that system is pretty much mandatory
 
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Spike Strip

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It won't hurt to have the Decel system, and putting in a two-wire ICS with the VS and computer, like stock, will work, but you're adding complexity where you don't need it if you're going to desmog. Plus, those Emissions computers are known to fail and if (when) it does, you'll have to ground the ICS and you'll be back to square one.

This isn't going to happen on an FJ60

tenor.gif
 

CruiserWil

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I've run the 2F without the deceleration fuel cut system active and it's not an issue. Engine gurgles a little more during engine braking but it doesn't backfire. It's nice to have if you've got a functioning vacuum switch and computer but it's definitely not a game changer. Just a nuanced improvement.
It's mostly there to improve emissions.

So the next issue Is the fuel cut system on shut down to prevent dieseling. This IS important otherwise turning off the engine is a sputtering banging croaking affair as it gasps its last breathe before conking out.

The fuel cut solenoid doesn't require a vacuum source to turn on & off — only a switched 12V source. For just engine stopping use, it can be wired through the Engine fused circuit at the fuse panel. Then when the key is turned ON, it will energize and open the fuel passageway, and when the key is OFF, it will be de-energized and shut off fuel to the carb for a civilized shut down. The emissions computer isn't needed for Shutdown functionality.

As for a single wire or double wire solenoid, that's only a grounding issue. The non original FCS grounds through its threads into the carb body so it needs a switched 12V+ source, while the original 2 wire solenoid has its own dedicated ground wire which connected to the computer circuit.

If I were in your boots, I'd forgoe using the deceleration fuel cut system for now and drive the car without it and see how you like it. You might not notice it's missing.
But definitely hook up the engine shut off fuel cut system — that system is pretty much mandatory
I didn't know about the dieseling on shut down issue, thanks. And good to hear that the afterburning is only a minor issue in the absence of a catalyst. Weird to say but true--I haven't actually driven my (not so now) newly acquired 60 yet. It was really F'ed up by the PO.
 

CruiserWil

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It won't hurt to have the Decel system, and putting in a two-wire ICS with the VS and computer, like stock, will work, but you're adding complexity where you don't need it if you're going to desmog. Plus, those Emissions computers are known to fail and if (when) it does, you'll have to ground the ICS and you'll be back to square one.

This isn't going to happen on an FJ60

tenor.gif
Pretty jazzy signature, if that is what that is...! From what you and OSS are saying, I'll just wire the FCS to switched 12v. Thanks both.
 

micruz60

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No way you are out in the weeds, this is what MUD is about!!

:popcorn:

I've always enjoyed the sensation of the the fuel decel kicking in when coasting off of higher RPMS, but lately the 60 has been doing the afterburn popping and I will need to remedy that. My initial reaction was that it was due to using 91 octane non-ethanol fuel, for about three tankfuls, as that is when the afterburn began.
Procrastination on the desmog also is a factor, as all systems have worked great for twenty years. Also suspect is the operation of the air (smog) pump.

That whistling sound you describe is most likely coming from the J-pipe / EGR system, gasket leaks momentarily until heated up.
 

CruiserWil

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No way you are out in the weeds, this is what MUD is about!!

:popcorn:

I've always enjoyed the sensation of the the fuel decel kicking in when coasting off of higher RPMS, but lately the 60 has been doing the afterburn popping and I will need to remedy that. My initial reaction was that it was due to using 91 octane non-ethanol fuel, for about three tankfuls, as that is when the afterburn began.
Procrastination on the desmog also is a factor, as all systems have worked great for twenty years. Also suspect is the operation of the air (smog) pump.

That whistling sound you describe is most likely coming from the J-pipe / EGR system, gasket leaks momentarily until heated up.
Thanks for the whistle suggestion, but I don't have EGR or Air Injection anymore. Though I think you're right, it's a temperature/expansion issue, probably exhaust component related. But the whistle is steady, doesn't pulsate, as exhaust leaks often do.

If you have Air Injection & EGR, troubleshooting your popping issue has lots of interrelated systems to troubleshoot. Wish I could be of more help, other than suggesting doing the various tests outlined in the 2F Emissions FSM.
 

rhah

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Is there something I’m missing?

I have installed a couple of these high altitude desmoged carbs and have no issues whatsoever

bolt them on, plug it in, and poof your done motor runs great set your timing and walk away.
 

CruiserWil

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- if the TINY o-ring on the end of the FCS rots or tears off during install or extraction removal this can cause issues

- FTY to ALL whom install a new or pre-owned FCS 2 wire or 1 wire , you MUST kote the tip of with the micro black o-ring with some Olive Oil ,from wife's kitchen or Vaseline Jelly from your bathroom cabinet , or SOLID silicon paste .

any 3 will work well , now to be clear NOT too too much just a light skim kote , so it can rotate in freely as u wrench in the fcs , into any land cruiser

- I offer a NEW Updated , 2 Wire , Fuel Cut Solenoid , I had a special 1000pc run of the correct USA spec, 2 wire male connector device side , that come on ALL mine i hand out ...

- i will proudly say , after countless hours of research , i AM the ONLY Land Cruiser specialty Store GLOBALLY that has available a Period correct and quality function 2 wire land cruiser FCS, with correct OEM toyota connector plug installed and ready to roll .........

please review the Below link and technical Photos too , mines comes with a OEM toyota crushing gasket , again , i could and cant find another vendor globally that has a 1 wire FCS that includes the indeed safety related crush ring gasket , i do , and it is a required part 100% per me and the Mighty FSM from toyota

- i have indeed hooked more then well , many dozens at least i can say for certian , that install my 2 wire FCS , with correct corresponding plug and play connector housing profile , into a City racer FUJI MITSU japan made unit like u have going on , NO issues ever to report ....


thanks for your time

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of simply click these links \





matt

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Matt, I feel like I can tell you this and you won't get offended because we had a couple of Bullet-fueled friendly 1:00AM 'phone conversations a couple months ago. Stop with the advertising efforts when just posting replies in a regular technical thread.

I don't know how this msg will go, it's only meant as constructive criticism. I'm fully aware of and appreciate your excellent parts and service offerings without being unnecessarily exposed to them in technical discussions. I dislike little alligators on shirts too ✌️ ;):rofl:.

Your fellow late-night Bourbon Owl, Wil
 
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