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Discussion Starter · #1 ·
Seeking help. My '83 sj410 with Aisan carb cannot start, run, or idle without choke regardless of how warm engine is. The moment I open the choke, the engine dies. It also cannot run with or without throttle opening. With the choke on, it will run at high rpm, oscillation evenly between 2000 to 3000 rpm. Suspecting something to do with vacuum leak and/or blocked air jets.

Fuel supply is fine (new fuel pump) and ignition is fine. Battery is new. Engine was not used for 2 years and I am now trying to revive it.

Thank you for any tips on how to troubleshoot or fix the problem.
 

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There are no "air jets" - the carb is either incorrectly adjusted, the idle jet (fuel) may be blocked, or the carb may have an anti-diesel solenoid that is not opening.

If the engine has been sitting for two years I would suggest you get a carb kit and do a thorough cleaning of the entire fuel system, including replacement of the filter - maybe add a small inline filter between the pump & the carburettor - you may find that you have frequent blockages of the various jets until such time as all the debris in the system is cleared.
 

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I agree with Fordem, sounds like the slow running circuit us clogged with old fuel deposits. It may take several soakings of the carb body in cleaner to get it all cleared out.
 

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Discussion Starter · #4 ·
There are no "air jets" - the carb is either incorrectly adjusted, the idle jet (fuel) may be blocked, or the carb may have an anti-diesel solenoid that is not opening.

If the engine has been sitting for two years I would suggest you get a carb kit and do a thorough cleaning of the entire fuel system, including replacement of the filter - maybe add a small inline filter between the pump & the carburettor - you may find that you have frequent blockages of the various jets until such time as all the debris in the system is cleared.
Thank u for your suggestion. I will try to clean once again and replace the inline fuel filter. Yes, I meant fuel jet. But is there a way to test the anti dieseling solenoid? How is it triggered? There is no ECU in this model, I think. The engine dies immediately once I release the choke!
 

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If its dying immediately you release the choke ill put money on a blocked idle / slow running circuit blockage. Cleaning the jets is only 1 part, theres all the air bleed passages and fuel passages to get as well. You might be in for a strip down and soak fir a few days in a tub of carb cleaner

Checking the anti diesel solenoid us easy, it gets 12V from the ign switch at ign and start positions and pulls in with an audible click usually. If that's not working you will be hard pressed to get the car to run, even with the choke on usually.
 

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Discussion Starter · #6 ·
I will take your advice, time to strip it down again for a thorough cleaning.

Your comment about the solenoid makes a lot of sense. If default is shut, then no fuel into the manifold regardless of choke position.
 

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I will take your advice, time to strip it down again for a thorough cleaning.

Your comment about the solenoid makes a lot of sense. If default is shut, then no fuel into the manifold regardless of choke position.
Effectively yes, its a flow restriction not a full shut off on most carbs of that era. Symptoms of a shut one are engine cranks, fires, dies immediately, repeat

Yours starts and runs with choke so that says the anti diesel solenoid is working.
Its always possible its got dirt under it restricting flow but unlikely, unscrew it and have a look. Give the end of it a sniff, if it smells rank and like old varnish then you know where the issue is likely to be.

Your fuel sitting inside the carb was 2 years old, thats varnish deposit territory after sitting a couple of months, let alone 2 years.
 

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After two years the carb would have been bone dry - no fuel inside - and the anti-diesel solenoid, if there is one fitted (not all carbs have them, but they were used on Aisins) will completely block the idle circuit - the engine will still start when choked, because the action of closing the choke plate increases draw on the main jet to richen the mixture whilst starting.
 

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Discussion Starter · #10 ·
Latest update. After cleaning out the gunk in the jets and replacing the fuel filter, it can run without choke but still not idle. So, I think I need another round of cleaning.
 

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Yep, idle passages in the carb body will be crudded up. Did you clean the emulsion tube or only the jets?

At least you're making progress
 

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Discussion Starter · #12 ·
Yup, cleaned the emulsion tube. But I need to get a cleaning kit to get to all the tiny orifice. Have been using a strand of copper wire from wire wheel but can't reach all the orifice. Also the gasket is torn.
 

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Don't use wire. Scratches in those orifices cause bigger issues.
Soak in carb cleaner solution is the only option, carb on bench, fill float bowl till over flowing, walk away for 24 hours, empty, blow everything out with air. Repeat
That will get the cleaner to where the fuel usually sits.and gums things up.

Which gasket? If its the sealing one on the carb body top you might be ok, if its the carb to manifold then it will never idle properly
 

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Discussion Starter · #14 ·
Don't use wire. Scratches in those orifices cause bigger issues.
Soak in carb cleaner solution is the only option, carb on bench, fill float bowl till over flowing, walk away for 24 hours, empty, blow everything out with air. Repeat
That will get the cleaner to where the fuel usually sits.and gums things up.

Which gasket? If its the sealing one on the carb body top you might be ok, if its the carb to manifold then it will never idle properly
Thank you for your advice. Will do as recommended.

Yup, it's the gasket to the manifold and I think this it is the reason it is not idling. Previously, it was blocking the fuel passage!

Thanks for all the feedback.
 

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Two comments ...

- first - the only way a gasket will block a fuel passage is if it's the wrong gasket, or it has been incorrectly installed
- second - it's highly unlikely that a gasket between the carb and the manifold will be blocking a fuel passage, I've yet to see a carb that had fuel flowing through the manifold - coolant, yes - fuel no.
 

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Discussion Starter · #16 ·
first - the only way a gasket will block a fuel passage is if it's the wrong gasket, or it has been incorrectly installed
The entire passage was blocked by sediment. I had to clean it with toothbrush and carb cleaner! It was correctly installed, I can't see how it can be wrongly installed. Anyway, I can get the car running now without the choke, but can't reduce the idling below 1000 rpm without it dying.
 

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It was correctly installed, I can't see how it can be wrongly installed.
Some gaskets can be incorrectly installed, most can't - my point was that the correct gasket, correctly installed can't block a fuel passage - which you're now telling us was blocked by sediment.

Yup, it's the gasket to the manifold and I think this it is the reason it is not idling. Previously, it was blocking the fuel passage!
Not idling below 1000 rpm - go right back where we sent you before - clogged slow running circuits, idle jets, anti-dieseling solenoid and incorrect adjustments - all are still possibilities.
 

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Discussion Starter · #18 ·
I was careless in stating it was blocking the fuel passage. What I meant was sediment in the passage under the gasket, not the gasket itself. I only saw the clogged passage after prying off the gasket. My bad!

Hoping to buy a new set of gasket and then do a thorough cleaning once again.
 

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The slow running passages you won't get to with brushes etc, strip the carb, and soak the whole body in a bowl of carb cleaner for a couple of days. Blow out with compressed air

Do not use wire to clean out passages.

Depending on how much varnish is built up in the idle circuit, You may need to do this a few times.
 
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