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 Post subject: Intermittant misfire - 1986 Swift G13A (carb)
PostPosted: Wed Jul 12, 2017 11:46 am 
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Joined: Wed Aug 31, 2016 3:54 pm
Posts: 6
Location: New Zealand
Hi gang,

We are in New Zealand. We have a 1986 Swift 1.3, 3 door manual with a G13A. The headgasket was replaced about 12,000km ago by my son, who is a competent mechanic. The car has done 192,000km.

Recently, it has started dropping down to three cylinders - maybe fewer - whilst being driven. Sometimes 5 minutes after starting, sometimes 25 minutes - sometimes it doesn't happen at all.

Each time, my daughter (who is the only driver) says that stopping the engine and restarting it, immediately resets the engine back to normal for another 5+ minutes.

I have changed the plugs. The old ones looked identical to each other.

I have changed the leads for a new set.

I have changed the distributor cap.

I have changed the coil.

I have NOT changed the rotor arm.

I have NOT changed the distributor - which has an electronic pickup.

Any ideas folk, other than change the dizzy?

I'm not convinced that it drops only one cylinder. The plugs don't seem to show that. And it hasn't done this fault with me in the car. I'm wondering if it's just dropping LOTS of sparks when it happens, and all cylinders suffer equally.

I'm sure that it's on the electrical side, because of it going away when the engine is turned off/on.

Any thoughts on further fault-finding, folks?

Adrian


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 Post subject: Re: Intermittant misfire - 1986 Swift G13A (carb)
PostPosted: Thu Jul 13, 2017 8:56 am 
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Joined: Mon Aug 25, 2003 12:00 am
Posts: 17515
Location: ACT
The issue could be fuel-related. Maybe an issue with the pump or fuel cut solenoid?

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 Post subject: Re: Intermittant misfire - 1986 Swift G13A (carb)
PostPosted: Fri Jul 14, 2017 11:16 am 
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Joined: Wed Aug 31, 2016 3:54 pm
Posts: 6
Location: New Zealand
Thanks for the idea! I hadn't thought about fuel delivery. I'll investigate.

Cheers!


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 Post subject: Re: Intermittant misfire - 1986 Swift G13A (carb)
PostPosted: Fri Jul 14, 2017 5:22 pm 
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Joined: Mon Aug 25, 2003 12:00 am
Posts: 1526
Location: Londoninium
Ignition module in the distributor could be your culprit. Mine suffered the same symptoms at about the same distance travelled. Its the Crescent shaped electrical bit in the distributor. Mitsubishi part. Try and find a mitshibishi part not a Suzuki part as at the time Suzuki wanted $400 mitsibishi wanted less than 100. Aftermarket may be available today. The original part is a Mitsubishi part.
Change rotor arm at same time.
Hope that helps.
GTP


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 Post subject: Re: Intermittant misfire - 1986 Swift G13A (carb)
PostPosted: Sun Jul 16, 2017 4:54 pm 
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Joined: Wed Aug 31, 2016 3:54 pm
Posts: 6
Location: New Zealand
Thanks GTP - you're actually the second person to suggest that to me, today - so I'm inclined to think it's likely. I'll follow up.

Cheers!


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 Post subject: Re: Intermittant misfire - 1986 Swift G13A (carb)
PostPosted: Mon Jul 17, 2017 9:45 pm 
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Joined: Mon Oct 12, 2015 11:30 am
Posts: 81
Location: Wellington
The ignition module is the only item in the ignition system that you have not replaced, otherwise I would have suggested the other items you have replaced already.

Mine did similar, it was the frost plug on top of the head that was leaking coolant down into the spark plug chamber causing it to short out. But mine is twin cam efi, so you probably would not have that issue.

As mentioned, fuel delivery, fuel pump (sock too), filter, lack of fuel with a sticky float in the carb or something funny? I'm not too flash with carb knowledge....

Also, props on writing a detailed post. Much easier when you have all the info!
Make sure to post back here when fixed, we love to hear the results :D

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A Kiwi learning to fly in a Mk1.


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 Post subject: Re: Intermittant misfire - 1986 Swift G13A (carb)
PostPosted: Sun Jul 30, 2017 10:01 am 
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Joined: Wed Aug 31, 2016 3:54 pm
Posts: 6
Location: New Zealand
Thanks for the comments, mate! :-)

Some more info has come to light, from my daughter. (She changed the fuel filter, which was full of crud, but that made no difference.)

The misfire seems to happen when she decelerates at speed, without touching the throttle for a few seconds, and then tries to speed up again. She pulls over, and has to leave the car switched off for around 30 seconds, and it then fires up normally.

To me - off-throttle deceleration is high vacuum for a few seconds. I'm suspecting that the carb has a vacuum actuator that operates under those conditions, but sticks, and takes 30 seconds or so to let go.

Do the simple carbs on the 1986 G13A manual have anything like an overrun cutoff? I could imagine that when the car "fails", there's something that keeps on restricting the fuel flow, instead of resuming as soon as the throttle is mashed again.

I've asked her that next time, leave the engine running in idle, and see if it cures itself after 30 seconds. I want to see if the switching off of the engine is crucial to it "resetting".

Any thoughts, gang?

Adrian


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 Post subject: Re: Intermittant misfire - 1986 Swift G13A (carb)
PostPosted: Sun Jul 30, 2017 12:58 pm 
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Joined: Fri Oct 25, 2013 6:59 pm
Posts: 16
Location: Brisbane
hi mate:)
i'm not a mechanic, but the problem you are describing is the advance weights in the dizzy.
they are sticking under load and just need to be pulled apart and cleaned and lubed, then you'll
be all good :)
best of luck with the job and have fun :)


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 Post subject: Re: Intermittant misfire - 1986 Swift G13A (carb)
PostPosted: Sun Jul 30, 2017 2:47 pm 
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Joined: Wed Aug 31, 2016 3:54 pm
Posts: 6
Location: New Zealand
Thanks man! Yet another possibility that I hadn't thought of. Thanks for that - I'll give it a go. Can't hurt.

Makes me wonder if it could be the vacuum advance sticking too. But whichever, if I clean and lube all the bits in there, it'd address both possibilities.

I'll report back.

Adrian


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