Troubles after carburetor rebuild

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Q23456789
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My tercel:: 1984 4wd Tercel, stock

Troubles after carburetor rebuild

Post by Q23456789 »

Hello! This is my first post here, but I have been lurking around on this forum for a little while now. I recently bought a 1984 Tercel 4wd from a friend of mine, but the car has been sitting for around 10 years. It ran, but the carburetor was dumping fuel right into the intake so I figured it wouldn't be a bad idea to rebuild it.
I found the FSM, watched a video on rebuilding the carb, bought a rebuild kit, and set to it. As I tore the carb down, I dipped everything that wasn't plastic into a bucket of carb cleaner over night. Put the carb all back together according to the FSM. Everything went together with little trouble. I did not check the two solenoids for operation, I don't know how critical those are. I adjusted the float to the specs in the FSM. I reinstalled the carb onto the car and that's where my problems started. It's hard to start but I can get the car to start, but it doesn't idle very well. It started out idling very high, around 3500 rpms, and while it was sitting there it was just after firing out of the exhaust. I adjusted the idle down once it warmed up, but the idle fluctuates a lot. It goes back and forth between 1000 rpms and 2000 rpms. It does it very erratically, in no pattern or anything. I can't find any vacuum leaks and am assuming it is some over fueling issue. The FSM doesn't show any external way to adjust fuel mixture, other then the idle mixture screw that you need to drill out the plug for. I have left that alone because I am assuming it's something I did in the rebuilding process that has caused this.
So my question is probably obvious. I am wondering where I should start to track down this issue? Should I tear it down again and look to see if anything is wrong? Some kind of adjustment that I don't see? Thanks a lot for any help!
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Petros
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Re: Troubles after carburetor rebuild

Post by Petros »

it behaves that way when it has a vacuum leak. double check all your routing, condition of all the reused vac lines, and use the FSM test process to verify if everything on the carb is working.

the solenoids will not cause that behavior, so do not assume they are bad yet.

You could have an internal vac leak if you miss-installed a gasket or O-ring inside the carb. there is a big O-ring under the top cover that just sits on top of the cab center body, it is easy to either forget to put it in, or to have it move out of position when you install the top. It will be hard to start and run crappy at lower speeds if this O-ring is not in place.

so if you can not find anything external, it might be worth pulling off the top and verify the big rubber o-ring that goes under the top cover is properly in place.

Good luck.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
Q23456789
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Joined: Sat Sep 30, 2017 6:06 pm
My tercel:: 1984 4wd Tercel, stock

Re: Troubles after carburetor rebuild

Post by Q23456789 »

The O-ring you're talking about is the one for the air cleaner to the carb? I am trying with the air cleaner off right now, and the hose that goes to it plugged. If you're talking about one inside the carb, then I might have missed it because I don't remember one other then the little one on the venturi. I have verified the solenoids to ne working. The carb seems to be flooding out the motor. Plugs are wet and I can see liquid fuel on the butterflies when it's running. If I put my hand over the top of the carb while it's running, I soak my hand with fuel misting upwards. Thanks a lot for the response.
xirdneh
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Re: Troubles after carburetor rebuild

Post by xirdneh »

that o ring is about 3/8" diameter and its under top of carb. its not big. original o ring is fat. the o ring in some carb kits is thinner and looks more like a cut off piece of black tube. sounds like you installed it. something else is wrong. take the carb apart and do it over. i do not dip the carb parts anymore. i just blast the thing with spray carb cleaner then blow it out with air. when using carb spray blow it into every hole and make sure it exits somewhere (no clog). you must have missed something in the re-assemble
and check the rear solenoid. if it is not working it will never idle right
rear solenoid can be single or double wire depending on whether you have early or late model tercel
Love those Tercell 4x4 wagons but they sure suffer from road noise.
Q23456789
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Joined: Sat Sep 30, 2017 6:06 pm
My tercel:: 1984 4wd Tercel, stock

Re: Troubles after carburetor rebuild

Post by Q23456789 »

I will see about disassembling the carb again and see if I missed anything. I have verified both solenoids to be working now. I am going to check for vacuum leaks in the morning, if I don't come up with anything then I will pull the carb back apart and see what's up. Thanks.
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ARCHINSTL
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Re: Troubles after carburetor rebuild

Post by ARCHINSTL »

This is one of (if not the) longest threads here; 65 posts at last count.
You may find some nuggets here:
viewtopic.php?f=4&t=1372&hilit=idle

Tom M.
T4WD augury?
"Oh, do not ask, 'What is it?' Let us go and make our visit."
T.S. Eliot - "The Love Song of J. Alfred Prufrock"
"Now and then we had a hope that, if we lived and were good, God would permit us to be pirates."
Mark Twain
jimcrazy
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Re: Troubles after carburetor rebuild

Post by jimcrazy »

if you left the O-rings out it will run like crap,,they are between the two phillip head screws,,the left in the pic is there and the right side is missing,you need both to be there
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xirdneh
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Re: Troubles after carburetor rebuild

Post by xirdneh »

i have never seen one on right (per picture secondary) and i have disassembled at least 30 of these carbs.
Love those Tercell 4x4 wagons but they sure suffer from road noise.
Q23456789
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Joined: Sat Sep 30, 2017 6:06 pm
My tercel:: 1984 4wd Tercel, stock

Re: Troubles after carburetor rebuild

Post by Q23456789 »

I know the two I disassembled only had the one o-ring on the left, so I only put one new one on.

I think that I have determined that this isn't a vacuum issue, but am not 100% sure. I couldn't find any leaks with carb cleaner or a stethoscope. I did go through and plug all of the vacuum lines off of the carb except for the vacuum advance, and it still runs like crap. It did seem to be dumping less fuel in, but I am not sure on that.

Another symptom that I have noticed is it hesitates when you give it throttle. If you go hard on the gas it will stumble and drop rpms and then eventually climb up in the rpms like it should.

I am going to pull the carb and go back through it again and try to make sure everything is right. Hopefully I find something obvious and can fix the issue. Thanks to everyone for the help.
Q23456789
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My tercel:: 1984 4wd Tercel, stock

Re: Troubles after carburetor rebuild

Post by Q23456789 »

So an update for the day:
I re-did the carburetor and found the idle jet to be plugged, and got that unplugged and able to flow. I also found that the idle mixture screw has been messed with before, the plug that I thought was it turned out to not be it. So I set that to what the FSM says the base setting should be (3 1/4 turn from bottom).

I put the carb back on the car and it ran great for a minute or two, and then the bowl over filled and started dumping fuel out of the two bowl breathers at the top of the carburetor. It flooded the engine and killed it pretty quick.

So I am wondering what could cause the over filling of the bowl? I know the float/needle valve being set incorrectly can do this, but am very sure that I set it up right to the FSM specs. I wonder if the fuel pump putting out too much pressure could do this? I just replaced the pump, because the old one was bad from sitting. Is it possible that the return hose to the fuel tank is plugged and that is causing excess pressure on the carb inlet side of the pump? I tested fuel pressure from the pump while cranking with and without the fuel return hose connected. With the return hose connected I was getting about 3.5 psi, and without I was getting about 3 psi. I am assuming those numbers would be further apart if the car were running and not just cranking. I am working on clearing the fuel out of the intake right now to hopefully try running it with the return line in a bottle. Any other ideas, or anything that I might be missing?
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Petros
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Re: Troubles after carburetor rebuild

Post by Petros »

sounds like the needle valve is leaking, I test mine (with cover off) by gently blowing in the fuel inlet and lift the float and see if I can cut off the airflow. could be crud caught in the needle valve, you just blow it out. visually inspect valve seat for damage (magnifying glass and strong light is helpful to check it). could also be float is water logged (fuel logged?). test float by putting it in jar of gasoline and see if it floats.

possible fuel pressure it too high, but those numbers are within acceptable range as I recall.

good luck.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
Q23456789
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Posts: 17
Joined: Sat Sep 30, 2017 6:06 pm
My tercel:: 1984 4wd Tercel, stock

Re: Troubles after carburetor rebuild

Post by Q23456789 »

I just got finished running it, and it seems to be running pretty good right now. I put both the feed line and the return into a full gas can and it seems to have stopped flooding. So I am assuming one of two things. Return line is plugged, causing excess pressure. Or like you said Petros, a chunk of crud in the needle valve seat that got dislodged when I tried to clear the flood.

But anyways, it RUNS right now. It doesn't run great though, the idle is a little rough and it kind of bounces around. I am guessing that's just a vacuum leak that I am having a hard time finding. When I shut it off though, it kind of diesels for a second and then starts bucking really hard, and then backfires out of the intake and dies. It blew off the brake booster hose the first time it did it. I am not sure what is causing this, but if I fix this I am assuming it will fix the idling issue. I drove it just a few hundred feet and it seemed to do fine with that.

Any ideas and pointers are helpful and appreciated, thanks very much!
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Petros
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Re: Troubles after carburetor rebuild

Post by Petros »

check your spark timing is correct (about 10 deg BTDC is good), too much advance will make it backfire.

you may want to adjust your idle mixture, though I do not think it wild cause back fire if it is off. You can do it by "ear", by screwing the mixture screw in and out a little at a time (at the correct idle speed) until it runs smooth. Engine must be warm and choke fully open.

Sometimes too lean can also make it run weak and back fire, usually just a "pop" out the exhaust. keep looking for any vac leak, it will make it run lean. Use a can of carb spray and with it running, give it puffs around different parts of the engine/vac lines, if the speed changes at lone location, that is where the leak is located.

Also, I can not usually get the fine tuning of the adjustments correct unless I install the airfilter housing with a good filter element in it. I think it changes the air flow/mixture a little with the air filter assembly in place.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
xirdneh
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Posts: 2121
Joined: Thu Aug 04, 2005 11:38 am
My tercel:: 87 tercel 4x4 wagon w/reringed engine, 83 tercel 4x4 wagon w/salvaged engine and 4.1 Diff's
Location: seabeck, washington, USA

Re: Troubles after carburetor rebuild

Post by xirdneh »

the original needle seats has a small very fine mesh screen on inlet side
kit does not come with one
they sometimes break when removing them or when trying to install on new needle seat
they are delicate
did yours have one?
Love those Tercell 4x4 wagons but they sure suffer from road noise.
Q23456789
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Posts: 17
Joined: Sat Sep 30, 2017 6:06 pm
My tercel:: 1984 4wd Tercel, stock

Re: Troubles after carburetor rebuild

Post by Q23456789 »

It had a filter on the seat, but it was broken and had a hole in it. I ended up putting it all together without the filter. I checked timing without pulling the vacuum advance hose, and it was sitting around 20 degrees. I need to pull the hoses off and see what its at. I messed with the idle mixture screw a little bit, but I didn't notice any real change in how it was running. I am guessing it's just because the idle is too rough to really see any change. I still think I might have a small vacuum leak, but I sprayed like a can and a half of carb cleaner all around and couldn't find anything. I might try and smoke test it later and see if I find anything. Thanks again for the help.
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