Submitted by bill on Tue, 01/14/2020 - 01:15

1978 Carburetor

I guess something always needs go wrong. Woofed up one of my main jets (see photo 3 below) with an ill chosen screwdriver. Didn't think I was going to get it out for a while. Ground down a big, nice Snapon screwdriver I've had for years because the fit was perfect - and it worked. I guess I have a special "jet" screwdriver now. 

Now wondering - can I use this jet as long as the hole is good? And where do/would I get a replacement, Toyota, SOR?
 

carb

 

Looks like a small 1/4" drive, 9mm Snap-on socket fits for the hard to reach Power Valve but a 6pt. deep 9mm would be better.

carb 1

carb 2

carb 3

 

Two strange things about my venturis: 
1) Were not "rattle" loose but not very tight either... 
2) Both were "double" (with the number 1) and appear to be the same (no triple)?

Everything looks original - no messed up screws, etc.?

EDIT:
Found this (below) in a closed Mud thread... I did mark mine and put them back the same way.



"Question: Are the venturis in this carb supposed to be the same? The fsm indicates that there should be one triple and one double venturi. The attached picture is what I found inside my carb. Could this be causing my idle problem, or is this correct as pictured?

Pin_Head reply:
I have a disassembled '78 carb (April 78) and the primary and secondary nozzles appear to be identical by everything I was able to measure. Never the less, I marked their primary and secondary locations in case there is some internal difference that is not obvious. This is unlike other years, where the primary and secondary nozzles are different. If I had to guess, I would pick the one on the left as the primary, because it has more carbon on it than the other one. My experience is that the more time you spend paying attention to where things were located during disassembly, the more likely you will succeed."

FJ40Jim reply:

FSM was written for 1975 2F, which has single ring and double ring boosters.

77-later carbs are double/double. There are differences in the emulsion tube and air jet, so try to keep the boosters in the correct hole.


 

Got the carb back in. Short test run with the idle/air mix screw just set at the 1 and 1/2 turns out. All the stumble from idle to higher rpm is gone and driving along in gear I no longer get the on/off the gas pedal "jerk" of the engine trying to get the RPMs up.

Opened up the main jet to 1.50. Need more time to test adjust.

And now I have new SST carb tools, special jet screwdriver and a chopped off 12mm open-end. Never found new jets for sale, and ended up with 2 rebuild kits. Got a Keyster kit from Kurt. Then of course the secondary was bad. Kurt didn't have one in stock, Napa ordered an alternative instead of the correct Hygrade number I gave them. Finally got the Hygrade (older one I think - had copper washers, etc.) so now I have a few spare parts.

 

sst 1My special custom ground Snap-on carb jet tool with the black handle.

 

sst 2

November 07, 2012

Carburetor was great for a while. Then I left a store in San Mateo to drive home a few days ago and started getting sputtering and bad "off-idle" again. Got home and stuck a tach on the hot engine and the idle was low so I set it back to 650 and adjusted the idle/air intake screw again. Ran better and the next few short trips seemed ok but wasn't running like it was when I first put the carb back on. Went to vote yesterday with the added bonus of finding some dirt to drive/park on (behind the local Fire/Poll station). On the way home started to sputter again - dirty gas like. Took a closer look at the carb and the accelerator pump was completely locked up.

Pulled the carb again today and found the accelerator pump, pump outlet and ball all working fine - but the spray jet (just the small hole itself) was completely clogged with a very small chunk of gunk. With the good seal/pressure the pump could not push gas out the jet. Very gently took the smallest drill rod I could find, loosened up the gunk in the hole and blew out a little splatter of brown grunge. This after the carb body had earlier been dipped, sprayed out repeatedly with air, carb cleaner sprayed through all passages (that same jet a number of times), etc. Everything else in the carb still looked spotless (new gas line filter put on earlier).

Only thing I can figure is a small piece of gunk was left hidden somewhere (like the base of the pump around the ball, etc. where I cleaned out a lot of stuff earlier) and later worked it's way up to the jet after a few days. Now everything is back on the truck and the pump is delivering a strong shot of gas from the pump jet. Test drive maybe tomorrow. 

 

November 23, 2012

More fuel delivery problems. The truck has been running great. Filled the tank yesterday and had a conversation with 2 guys from San Salvador in a nice jeep - they were very interested in the 40 - said they were common back there. Started home feeling good - short run on 101 at about 67 mph (iPhone speedo). When I pulled off the freeway I heard what sounded like maybe a backfire or two and then at 30-35 mph the engine started to miss - kind of like big "flat" spots of no gas. Stopped and looked around the engine, etc. Pulling the choke off and on helped me manage to limp it back home. Happy Thanksgiving 

Pulled the air cleaner this AM and can't see anything around the carb. Seems to idle fine but any gas and you get one normal-like rev and then it dies. If I pull the choke and turn the key it starts and revs up and then just dies. Do it any number of times and it continues to start - and then just dies. I'm thinking maybe the fuel pump (which I think is probably 30+ year old original) is my next adventure? Also wondering about the old worn rubber/new gas in the pump that came up earlier, etc. 

Update: Don't think it's the pump - the glass level seems to maintain a dot-level amount of gas...
Another question/possibility... maybe the main nozzle fuel circuit of the carb primary is now plugged with the same weird stuff that got in the accelerator jet?

Note: ICS makes "Click" sound when carb connector is plugged/unplugged w/ KOEO

 

Third time's a charm? I really appreciate all the good experience I'm getting removing/installing the carb.

Can't see anything at this point. Seems to me like maybe the accelerator pump (working well now) supplies some gas and that's the squirt the engine runs on until it dies. Need to pick up a can of spray carb cleaner. Dumb question - where are the other main feed points I should be looking at, primary venturi feed and ...?

Maybe should have tried to figure out how to check the ignition stuff first...


number 3 rebuild

 

Don't know if this could cause the current problem but it can't be good. This O ring looked OK and I didn't change it (live and learn). Kind of dumb considering it could be 30+ years old. At least I've found something.

 

click

Can't find blockage anywhere else with the carb spray. Replaced the Power valve with a new one from the Hygrade kit (even though it has a plastic part) just for heck of it.

So if the o-ring crumbled and got stuck in the idle passage, then it could have caused the lack of idle and other problems.

Put the carb back in with a static 1-1/2 turns out on the Idle mixture adjusting screw. Seems to start and run just fine (idle needs adjusting). So it must be that torn O ring in the Solenoid Valve? Strange that little rubber part made the truck nonoperational. I did put another Power Valve in but the original looked OK. 

 

Correction - looks like a small 1/4" drive, 9mm deep Snap-on socket is a perfect fit for the that hard to reach Power Valve.

carb 1

proper power valve

 

 

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