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 Points Gap and Dwell

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edlithgow
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PostSubject: Points Gap and Dwell   Sun Sep 27, 2015 1:54 pm

The Car (Daihatsu Skywing, Like a G10/G11n Charade) has rather suddenly stopped idling.

It'll start, and run if I keep the revs above about 1500, but it stalls out if I take my foot off the accelerator. Hasn't recently run out of petrol or experienced any other problems that seem especially likely to have introduced dirt to the carburretor.

I havn't adjusted the points since I got it, so I thought I'd better start there. On the Skywing it seems more difficult than I remember.

Firstly, the distributor faces to the rear, so you can't really see what you're doing.

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I tried using a mirror but then all your actions are reversed. This would take a long time to get used to, and you might not be able to walk once you had.

Short of lowering myself head-first into the engine compartment, Mission Impossible stylee,

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my best bet might be to rig up a webcam and laptop so I can see what I'm doing. I tried this but still couldn't see very well. I'll try it again with a light tomorrow.

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The Charade G10 engine manual (distributor seems identical and the points look like a Nippon-Denso design) pretty much ignores the points gap. It specifies the heel gap, and gives the same figure for the points gap as "reference information" . I'm surprised these figures are identical, since it doesn't seem to necessarily follow, but maybe they designed it that way deliberately.

Points gap and heel gap are clearly related, but I'm not sure if its enough just to set the heel gap and assume the points gap will be correct. For one thing, I've lightly filed the points which might alter the relationship a little.

They perhaps ignore the points gap because they tell you to check the dwell angle. I don't have a dwell meter here and would probably have trouble finding anyone who knew what one was, though I suppose I could get one sent from abroad or possibly find a high-end non-automotive meter that did duty cycle. I had a Gunson meter in the UK that did tach and dwell but its probably in landfill by now.

I suppose an ordinary analogue meter reading resistance would tend to average a rapidly oscillating signal like the primary ignition circuit, due to its mechanical inertia, so its indication would be proportional to dwell, but I dunno if it'd be linear or accurate enough to be useful.

Would it be worth measuring the dwell angle "statically" (i.e. with the engine cranked manually) , fitting a pointer to the distributor-arm and directly measuring the angle it moves through while the points are open/test light is off?
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Justwatching
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PostSubject: Re: Points Gap and Dwell   Mon Sep 28, 2015 5:27 pm

I've not had to get very involved with this part of the ignition system, only change points and set the gap with a feeler gauge.

Basically, my knowledge is limited here.

"I suppose an ordinary analogue meter reading resistance would tend to average a rapidly oscillating signal like the primary ignition circuit, due to its mechanical inertia, so its indication would be proportional to dwell, but I dunno if it'd be linear or accurate enough to be useful."

Hhhmmm. I'm not convinced it will work, though I can't tell you why it wont work. I guess the existence of dwell meters and a dwell angle function on automotive multimteres suggests the resistance reading from a regular multimeter wont cut it.

"Would it be worth measuring the dwell angle "statically" (i.e. with the engine cranked manually) , fitting a pointer to the distributor-arm and directly measuring the angle it moves through while the points are open/test light is off?"

I have (somewhat) more confidence in this method. Feel free to try it out, as an experiment if nothing else.
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edlithgow
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PostSubject: Re: Points Gap and Dwell   Tue Sep 29, 2015 12:12 pm

Did the webcam thing again (with a light this time) and got the points gap set more or less correctly, AFAICT. I used 0.018 and 0.020 " feeler guages as a go/no go pair. Didn't seem to make it run any better, but at least it didn't seem to make it run any worse.

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I'll re-visit the dwell angle difficulty later, but for now fuel seems more likely a cause of the bad idle than sparks.

This means I'll probably have to try and understand the carb. Last time I tried that, I got a headache, and my choke stopped working.
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Justwatching
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PostSubject: Re: Points Gap and Dwell   Tue Sep 29, 2015 8:05 pm

Thinking about your problem, the symptoms don't really lend themselves to ignition points. If they're bad, they should affect the entire rev range, unless we're talking an ignition advance problem, but that would cause problems on the upper (not lower) rpm range.

Could always check for vacuum leaks if you want to procrastinate looking at the carburetor.


Last edited by Justwatching on Tue Sep 29, 2015 8:06 pm; edited 1 time in total (Reason for editing : because "point to points" sounds silly.)
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edlithgow
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PostSubject: Re: Points Gap and Dwell   Tue Nov 24, 2015 8:22 am

Passed inspection couple of weeks ago, which I know probably doesn't mean anything here but always puts me in a slightly celebratory mood, due to my past experiences trying to get my old bangers through the UK MOT inspection.

The idle seems to have improved, though I dunno why. I'd blown butane over the plumbing surrounding the carb, and over the intake manifold, but the engine note only changed when the gas was directed at the air intake, so I didn't detect any vacuum leak.

I doubt cleaning the fuel filter (see post in "cleaning air filter" thread) had any effect, but I suppose its possible the partial drain of the fuel tank removed some troublesome sediment.

In the US/Europe this might be more plausible, since water/alcohol phase separation is apparently now an issue there. I don't know if Taiwan petrol contains alcohol, but I'd have thought not, since there's no farmer grain-alcohol lobby, and the sugar industry (which used to produce lots of alcohol) was killed off ages ago by WTO membership eliminating protective tariffs.

There's a judder felt through the steering wheel which seems new but smooths out at higher speeds on the freeway. Initially thought it was tyre flatting, then (when it came back) maybe clu clutch slip/judder, but I noticed that one of the front wheels was pretty hot, so I guess either my brake caliper (just cleaned and lubed) is sticking on, or its a consequence of flipping my brake pads (see "Coke can for brake disks" thread) and I should flip them back again.

I didn't get to see the numbers on the (private) rolling road brake tester machine, and wouldn't necessarily believe them if I did.

I'd HOPE if it was really bad they'd fail it even in Taiwan, but perhaps I can't rely on that.

Options are then to take it to a stricter govt. testing station (but then failure could be inconvenient) or work up a DIY brake-testing protocol.

Watch this space, but don't hold your breath.
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Justwatching
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PostSubject: Re: Points Gap and Dwell   Tue Dec 01, 2015 12:44 pm

So one wheel is hot, but it doesn't pull to that side?

Why did you flip the pads? I'm too lazy to go look at the other thread.
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PostSubject: Re: Points Gap and Dwell   Fri Dec 04, 2015 12:45 am

Justwatching wrote:
I'm too lazy to go look at the other thread.

Oh, go on! Its got pictures, and it elicited even more than the usual level of patronizing pontification when copied to Honest John:). I didn't mention the flipping, though, since I was getting enough flak (though poorly aimed) as it was.

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This problem would give them a more specific target, but I doubt they'll see this thread.

I think I flipped the pads by accident, and then couldn't be bothered to flip them back because I didn't think it would matter. I'd guess the consequences would be:-

Negative

Reduction in clearance (peaks coincide)
Reduction in braking efficiency (reduced contact area)
Increased pad wear

Positive?

Slight "flatting" effect as the pads and disk wear in to each other.

Could be reduction in the drivers side efficiency is causing the passenger side to do all the work, so its getting hot, or it could be the passenger side is sticking on. I favor the latter explanation, though it does suggest my caliper cleanup didn't do any good and may have done some harm (though I don't see why).

The only rubber-compatible grease I could find (bought in a motorcycle shop near Osaka airport just before leaving Japan) is silicone base, and IIRC tops-out at 180C, which isn't really high enough, so this'll likely have melted off the pins. I could wrap the whole pin in PTFE  next time (I just did part of the threaded portion) but this might rumple up and interfere with free movement.

Best guess is a sticking piston. Didn't take these apart last time but I might have to, preferably after I've got a new brake hose so I can replace that at the same time.

Doesn't seem to pull markedly but I was driving in traffic so couldn't really test emergency stops. Might have time to do that this weekend
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PostSubject: Re: Points Gap and Dwell   Fri Dec 04, 2015 10:22 pm

I stopped reading when they said you were putting lives at risk. What, by rubbing the brake disc with aluminium foil? I'll be able to see out my anus if I roll my eyes any harder.

If you think you've flipped the pads, flip them back.

When I said about pulling, I meant drifting off to one side when you let go of the wheel (not under braking). That's if it's sticking on. If sticking off, then yeah, you'll have to stamp on the brakes and see which way it goes. Or, take it to a garage and get them to put it on the brake rollers which will show how much force each side is contributing.
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edlithgow
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PostSubject: Re: Points Gap and Dwell   Sat Dec 05, 2015 2:33 am

Justwatching wrote:
I stopped reading when they said you were putting lives at risk. What, by rubbing the brake disc with aluminium foil? I'll be able to see out my anus if I roll my eyes any harder.

Pity. You missed the "Tile Grouting Trick", which I'd hoped would upset the PPA's even more, but perhaps they were all apoplexed-out by that point.

(It was a coke-can, not foil)

Justwatching wrote:
Or, take it to a garage and get them to put it on the brake rollers which will show how much force each side is contributing.

Call me prejudiced, but involving the pros is for me always something of a last resort, especially here where I'd have to get their bullshit translated.

In this case the fault was noted on leaving a rolling-road tester, so it might not have been detectable (perhaps the gadget is broken) or they might not have wanted the hassle of failing the car (which could lead to loss of repeat business) and communicating the failure reason to me, since I don't speak Mandarin or Taiwanese.
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PostSubject: Re: Points Gap and Dwell   Sat Dec 05, 2015 4:09 pm

edlithgow wrote:
It was a coke-can, not foil

Scrunched up aluminium. Aluminium foil. Inconsequential difference.

edlithgow wrote:
Call me prejudiced, but involving the pros is for me always something of a last resort

I get that, hence why it was listed last.

I can't imagine they'd charge much, if anything, as it only takes a moment to put it on a roller and hit the brake peddle a couple times.

edlithgow wrote:
since I don't speak Mandarin or Taiwanese.

Haven't you been living there for some years now?
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edlithgow
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PostSubject: Re: Points Gap and Dwell   Sun Dec 06, 2015 1:15 am

Justwatching wrote:


edlithgow wrote:
since I don't speak Mandarin or Taiwanese.

Haven't you been living there for some years now?

Yeh, I get that a lot. Sometimes I lie about it if I think I can get away with it.

People seem to assume you just absorb language from the environment, but you have to actually work at it, and laziness, stupidity, inefficiency leading to lack of time, lack of motivation, and perhaps a certain expatriate alienation are all potential obstacles.

Oh, and of course it's F-ING CHINESE! That's a bit of an obstacle too, though most other people don't find it insurmountable.

I don't actually NEED Chinese for daily living, and sometimes (as in this case) its convenient not to have it, though pretending not to have it would usually work as well. When I do need it I can usually get my gf to translate for me.

I also find the teaching job soaks up most of my theoretically free time, which doesn't seem to apply to most people so I must be doing it wrong.
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