Carburetor advice

Electron1

Electron1

Expert Member
Joined
Jan 29, 2009
Messages
4,229
Reaction score
199
Location
Joburg
I have a 1989 Toyota Corolla 1600 4A-F
It suddenly has stopped idling when hot. It will idle just after starting for a few minutes and thereafter will die whenever it should idle. I can restart immediately and it runs fine. If i carefully add throttle after restarting it may then idle for a bit but hunts between 800 to 1500 rpm. It seems that there is no fuel

I have tried replacing the fuel and air filters, cleaning the carb with carb cleaner, checked the sight glass to see that the float level is fine, but cannot get to the root of the problem. It's got a sophisticated vacuum system (vacuum diagram)

Any suggestions?
I think I may have to take it in to a carb specialist - does anyone have any recommendations for one in Joburg?
 
Electron1 said:
I have tried replacing the fuel and air filters, cleaning the carb with carb cleaner, checked the sight glass to see that the float level is fine, but cannot get to the root of the problem. It's got a sophisticated vacuum system (vacuum diagram)
Click to expand...

Did you remove the carb to clean it?

Is it properly fastened to the inlet manifold? If it is, maybe remove the carb from the manifold - there should be a paper gasket in between carb & manifold. Take a look at whether the gasket is torn, maybe it's letting air in after the mixture was made, with a gap that gets bigger when your engine gets hot...

If it's in the vacuum system it could get interesting, but it's worth checking the pipes for obvious cracks, breaks, pinches etc.
 
klaas said:
Did you remove the carb to clean it?

Is it properly fastened to the inlet manifold? If it is, maybe remove the carb from the manifold - there should be a paper gasket in between carb & manifold. Take a look at whether the gasket is torn, maybe it's letting air in after the mixture was made, with a gap that gets bigger when your engine gets hot...

If it's in the vacuum system it could get interesting, but it's worth checking the pipes for obvious cracks, breaks, pinches etc.
Click to expand...

No, I haven't removed it at all, just sprayed the carb cleaner with it bolted in place.
should I buy a new gasket if I remove it form the manifold?
Must check maybe bolts could have loosened. although it works perfectly except for idling, responds to throttle immediately.
 
Electron1 said:
No, I haven't removed it at all, just sprayed the carb cleaner with it bolted in place.
should I buy a new gasket if I remove it form the manifold?
Must check maybe bolts could have loosened. although it works perfectly except for idling, responds to throttle immediately.
Click to expand...

You should be fine with the old gasket if it's undamaged, but I've never seen a Toyota's setup, so it may be necessary to get a new one. Ask your local spares shop for advice about this. Maybe get some gasket paste to apply to both sides of the gasket before reassembling to create a nice seal.
 
I've never worked on that particular carb but the ones I have worked on had two sets of jets. A main jet(s) and an idle jet.
On two occasions I had an engine that would not idle properly (hunting) or the engine would just die when no throttle was applied and in both cases it was dirt stuck in the idle jet.

Open the carb, clean it carefully (no poking around with hard objects like pins/needles/nails as this can damage the jets) and reassembled with new gasket set.
 
Paul_S said:
I've never worked on that particular carb but the ones I have worked on had two sets of jets. A main jet(s) and an idle jet.
On two occasions I had an engine that would not idle properly (hunting) or the engine would just die when no throttle was applied and in both cases it was dirt stuck in the idle jet.

Open the carb, clean it carefully (no poking around with hard objects like pins/needles/nails as this can damage the jets) and reassembled with new gasket set.
Click to expand...
So you recommend that I remove the carb and check the jets or can I do this while it is still in place?
 
Electron1 said:
Is a leaky gasket likely to be the problem?
Click to expand...

That could be a problem. More air = leaner mix = bad combustion.
The idling is usually when the engine is shaking the most which could aggravate an air leak.
Spraying around the inlet/carb joints with an engine starter aerosol and listening if the engine changes speed is one way of trying to find air leaks.
 
Electron1 said:
So you recommend that I remove the carb and check the jets or can I do this while it is still in place?
Click to expand...

You'll need to unbolt the carb from the inlet manifold and open it up on a clean, level, working surface.
There are all sorts of goodies that like to jump and fall out and then roll away when you open up a carb. :)
Spring loaded ball valves, floating ball valves, spring loaded plungers, etc.
 
ponder said:
/looks at diagram and suspects he will have nightmares tonight
Click to expand...
Been having nightmares already - you should see the vacuum tubes connected to this thing!

Paul_S said:
You'll need to unbolt the carb from the inlet manifold and open it up on a clean, level, working surface.
There are all sorts of goodies that like to jump and fall out and then roll away when you open up a carb. :)
Spring loaded ball valves, floating ball valves, spring loaded plungers, etc.
Click to expand...

I think I better take it in to a specialist - any suggestions for one in JHB?
 
Check that the electrical connector of the idle cutoff valve is connected. Item 21934 on the carb diagram.
 
Last edited:
Stokstert said:
Check that the electrical connector of the idle cutoff valve is connected. Item 2394 on the carb diagram.
Click to expand...
Cool, will check that. I assume you mean 21934.
Will also check the bolts to the manifold are tight.
 
A dying carb is an absolute nightmare. You fix it for a while then it springs another hole somewhere else. If it starts doing this sort of thing regularly my advice is just replace it. You'll save a ton of pain. I'm speaking from experience here. We had a 316 carb-fed bmw, and it took us about a year of constant back and forth trying to fix the carb before we just chucked it and replaced it with a VW. From then on the car never gave us problems until the day we sold it.
 
I have tried unplugging and reseating the electrical connector.
The bolts to the manifold also seem tight.
Still cutting out on idle.
I am considering pulling it off and cleaning it out properly, just have no experience with doing this.
Budget is quite tight right now, so maybe this is the best option.

Any tricks I should know, before attempting, or should I go to professionals?
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X