I use WD40 with a pee tube to lightly and quickly spray the carb gaskets and the intake manifold while its cold and running - if the rpm's kick up there is your leak.
Aisin carburetor idle circuit routing (1 Viewer)
- Thread starter cbmontgo
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
Big Red Rocker,
I got my FJ40 running again today after replacing the distributor lockdown bolt. I did what you suggested and Yes,on the passenger side of the carb, I can see gas spraying down the throat at idle.
This shouldn’t be, right? What causes this?
I’ve read that vacuum leaks cause idle circuit problems, and then the carb gets adjusted improperly to keep the engine running at “idle”.
Is this your experience? Any wisdom on finding the vacuum leak?
Pighead, the spot where it seems to run “best” (though not well) is left of the BB. The BB is painted white so I can see it when I turn the dizzy CW, but the engine dies at that point. When I rotate the dizzy CCW, it will run. But I don’t see another mark, probably because it never got painted.
Pinhead, can you give me your experience on where the most probable vacuum leaks tend to be?
TIA
You need to download some free manuals.
www.cruisercult.com
Land Cruiser Factory Service Manuals (FSMs)
Factory service manuals (FSMs) for your Toyota Land Cruiser ! From the 1950s to the present!
www.cruisercult.com
I'm gonna guess that your timing is retarded. And that you have to turn your idle speed screw in to keep an idle. Try turning your dizzy body CCW, slowly and just a little at a time. See if you can turn out your idle speed screw a little bit. Look at your vacuum gauge. Repeat if it's working.
The line is TDC. Zero degrees.
thebigredrocker
SILVER Star
one thing to try is disconnect and plug the hose to the brake booster if you have one. Also as eluded to by others make sure the butterflys are almost close at idle.
Power is going to the carburetor's idle circuit cut-off solenoid?
Pighead, before I start the process of trying to reduce the Idle Speed Screw contribution, while adjusting timing, Whats your recommendation on a good starting place for my Idle Mixture Screw? I’ve seen several numbers.
Thank you, sir!!
A good enough starting place is anywhere it will run on it's own. Get it to idle somewhere and then adjust it to where you want it.
We have very different carbs, my turn count probably won't help. I might turn that screw in until it hits the linkage, maybe some more. Get it started and running on choke, turn in the screw and back off the choke until choke is off and it still runs.
EDIT: oops, disregard. I mis-read and thought we were still talking idle speed screw, not mix screw.
Last edited:
I think the common starting mixture setting is like 1 1/2 to 1 3/4 turns out. Go ahead and screw it all the way out, then look at the nose taper. Should be smooth, if it has a big ring pressed into from a gorilla tightening the screw - you need to fix that and maybe the seat if you want it to work correctly.
For the carb issue, it is most likely either a lack of idle fuel at the idle fuel port under the throttle plate or a air leak below the throttle plate allowing air with no fuel into the intake manifold. It is not always easy to distinguish these two possibilities, but you can try. First check for air leaks into the manifold. Block off all tube connections to the manifold, like the brake booster, PCV, and any other vacuum hose. Make sure they are all plugged.
Set the idle speed screw to the lowest RPM that it can run at and turn out the idle mix screw about 5 turns. Worry about setting the idle later. If It idles better after blocking off all the vacuum connections, then set the idle speed and mix and reconnect each hose one at a time and see where it starts to run poorly and that is your problem connection.
If is still idles poorly, then test any and all sealing surfaces of the manifold to the carb base or to the head or anything else connected to the manifold for leaks. I like using propane gas, because I can put a rubber hose on the end of my torch to get access to the bottom of the manifold where it seals on the head more easily than getting underneath the engine and spraying carb cleaner up at the bottom of the manifold and have it drip in my face. Your choice but be sure to check the bottom of the manifold gasket too. Also check for a cracked intake manifold under the carb.
If spraying carb cleaner or propane gas all around each millimeter of the sealing surfaces, it won’t idle better, then it may be a fuel delivery problem.
When you cleaned the carb, did you verify that the idle circuit was free of any obstruction and flowing freely? Did you shoot carb cleaner at the top of each port and see it streaming out the end? Did you run a piece of nylon monofilament line through it to verify it was open? If not, go back and check.
If all the passages are clear, then there could be a vacuum leak betweeen the top cover and the bowl as Jim mentioned. Check for flatness and if need be sand the sealing surfaces a bit with 240 grit silicon carbide paper on a glass plate with paint thinner as a cutting liquid to verify that they are flat and not warped or twisted.
After you have verified everything is sealed on the manifold and the idle circuit is free and flowing you have a much better chance of it idling properly.
Set the idle speed screw to the lowest RPM that it can run at and turn out the idle mix screw about 5 turns. Worry about setting the idle later. If It idles better after blocking off all the vacuum connections, then set the idle speed and mix and reconnect each hose one at a time and see where it starts to run poorly and that is your problem connection.
If is still idles poorly, then test any and all sealing surfaces of the manifold to the carb base or to the head or anything else connected to the manifold for leaks. I like using propane gas, because I can put a rubber hose on the end of my torch to get access to the bottom of the manifold where it seals on the head more easily than getting underneath the engine and spraying carb cleaner up at the bottom of the manifold and have it drip in my face. Your choice but be sure to check the bottom of the manifold gasket too. Also check for a cracked intake manifold under the carb.
If spraying carb cleaner or propane gas all around each millimeter of the sealing surfaces, it won’t idle better, then it may be a fuel delivery problem.
When you cleaned the carb, did you verify that the idle circuit was free of any obstruction and flowing freely? Did you shoot carb cleaner at the top of each port and see it streaming out the end? Did you run a piece of nylon monofilament line through it to verify it was open? If not, go back and check.
If all the passages are clear, then there could be a vacuum leak betweeen the top cover and the bowl as Jim mentioned. Check for flatness and if need be sand the sealing surfaces a bit with 240 grit silicon carbide paper on a glass plate with paint thinner as a cutting liquid to verify that they are flat and not warped or twisted.
After you have verified everything is sealed on the manifold and the idle circuit is free and flowing you have a much better chance of it idling properly.
Last edited:
Here’s what happened today:
I got it started and let it warm up. Plugged all the vacuum lines and set the IMS five turns out. Rotated the dizzy a bit CCW and adjusted the ISS down, then again, then again. Adjusted the IMS in to two turns out with no appreciable results. My best idle was 850 but finally got the timing set to the BB!! Woo hoo!!
The idle was smooth. I restored each of the vacuum lines one at a time with no change in idle.
Drove it around a bit and realized that I left my manual choke closed just a bit the whole time!! Phooey!
Started all over again.
Can’t get the engine to idle with the timing at the BB. Have to use choke to keep it running.
So I’m gonna pursue the vacuum testing with propane next. Good idea.
To answer your questions, I cleaned the carb very thoroughly when I put the kit in it. First, I soaked it in Gunk, then flushed it with spray cleaner. Then remembered that I bought a Harbor Freight Ultrasonic tub, so I soaked each third in the tub. Had problems, so I did it again. I thought I sprayed each and every passage clean. But I did not try the monofilament technique. Good idea.
I did not 240 grit sand the mating surfaces to ensure a good seal. Good idea.
So I’ve got more work to do. I can’t tell you how much I appreciate the troubleshooting ideas. When I start killing alligators, I forget about draining the swamp. Your big picture view is really helpful!
Pinhead
I’ve got a new question today. It may be related to my troubles with idle.
I’ve been reading a couple of the Toyota Tech Manuals to get mentally prepared for the Search For The Vacuum Leak. I also bought some hose and a ball valve to help me administer the propane as “surgically” as possible.
And then I noticed it. I don’t have a PCV valve! I have a new hose from the carb port to the crankcase port and they’re sealed up with good hose clamps. But there’s no PCV valve!! I just ordered one from Amazon, but I wonder if this could be contributing to my problems?
Scotty2
There is the vac leak.
That would do it but it won’t explain why capping this hose off did not make it idle better. Maybe the other end of the hose connects to the air cleaner or somewhere else above the throttle plate.
