Distributor vacuum advance diaphragm adventures

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oldfaithful
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Re: Distributor vacuum advance diaphragm adventures

Post by oldfaithful »

You don’t need them anyway, set your initial timing at 10 degrees BTDC and plug the lines use supreme gas and they work great.
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dlb
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Re: Distributor vacuum advance diaphragm adventures

Post by dlb »

oldfaithful wrote: Sat Sep 10, 2022 12:39 pm You don’t need them anyway, set your initial timing at 10 degrees BTDC and plug the lines use supreme gas and they work great.
I know they can run ok without them but I find they run better with them and get better fuel economy. Plus I've never wanted to pay for supreme gas, even less so with current gas prices. Plus I just like it when things work like they're supposed to.
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Mark
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Re: Distributor vacuum advance diaphragm adventures

Post by Mark »

I looked around my spare parts hoard and couldn't find my original butchered vacuum advance housing that I took apart. I assume I threw it out when I replaced it with a working spare from another distributor (I think I remember buying a distributor off ebay since there was something wrong with mine where sometimes it wouldn't provide spark when I tried to start it when warm. Anyway, the home-made one that I made on a lathe from aluminum I still have. It was for the original distributor on my 1st gen Tercel. It was the old points-type 6-volt distributor. I ended up replacing it with an electronic one from a 2nd gen Tercel. The aluminum disc-looking things are hollowed out inside. The diaphragm was cut from a Zodiac boat patch. I don't remember how I attached/sealed the diaphraghm to the rod. It worked fine, but I was semi-concerned about the length of travel of the rod vs the vacuum applied. I didn't do any calculations or measurements. It seemed to work fine when tested at idle, but I had no idea if the spark advance at different speeds was at factory spec.
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Nordical25
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Re: Distributor vacuum advance diaphragm adventures

Post by Nordical25 »

That is also a very nice idea Mark. It is great to see several ways of dealing this issue. I have also single port vacuum advances. I have noticed that Suzuki Samurai vacuum advance fits into Tercel 4wd single port model distributor. I have rebuilt a couple of spare distributors but never used them. So I would need to test that. However there will be time when these vacuum advances are neither available so it is great to do this kind of inspection beforehand.

This is the part I mean.
https://www.ebay.com/itm/191958940669

I attached also a separate picture of that unit so the info will last longer than Ebay-link.
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dlb
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Re: Distributor vacuum advance diaphragm adventures

Post by dlb »

Well, I made a few attempts but they all failed. I got it back together but it was leaking from around the crimp so I took it apart and gooped both diaphragms up on both sides of those and that was better but still no good. So, if someone has a good 2- or 3-port vacuum advance unit they'd be will to sell me, please let me know!
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rer233
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Re: Distributor vacuum advance diaphragm adventures

Post by rer233 »

Good luck finding a "good" one- I've got plenty of bad ones.
if it aint there, there's a good chance it won't break!
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Mark
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Re: Distributor vacuum advance diaphragm adventures

Post by Mark »

Bummer that didn't work. I think many of the Tercels came with single-port vacuum advances on the distributors. Judging by the emissions vacuum diagrams, one port comes from manifold vacuum and is to advance the timing at idle. The other hose comes from the throttle body (ported vacuum) and is to advance the timing at part throttle conditions. The single diaphragm vacuum advance version had the hose routed to the "ported" vacuum so there was no spark advance at idle. My 1st gen has the single diaphragm model. I've played around with switching the hose between ported and manifold vacuum advance and finally decided that drivability is best when it's hooked up to ported vacuum at the throttle body like it's supposed to be from the factory. Basically, a single-diaphragm advance should work fine for all models of Tercel (as long as you plug the other hose). You just won't have spark advance at idle so the idle speed will be slightly lower and you'll have to adjust it higher. I think the 3-hose version actually retarded the timing during certain conditions for emissions reasons.
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Nordical25
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Re: Distributor vacuum advance diaphragm adventures

Post by Nordical25 »

There are still then a couple of alternatives if these fixes do not work.

First option is to order a distributor rebuild service from Rockauto or to buy a complete rebuilt distributor. The distributor bearing can be a bit worn too so it may be worth of investment. Rebuilt distributors have according to my experiences a repaired vacuum advance diaphragm.

Second option is to get and try that Samurai vacuum unit. I did attach a picture of EU spec. vacuum lines.There is only one vacuum from distibutor to carb. And one vacuum at TVSV is capped already at Toyotas production line. So it seems as Mark says that second vacuum line is to make smoother idle.
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Petros
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Re: Distributor vacuum advance diaphragm adventures

Post by Petros »

that is interesting and good to know the Samari vac advance fits the same (I wonder if the whole distributor will also interchange perhaps?).

you can connect both the idle port and manifold port to the same vac port on the diaphrame with a simple T fitting, since they go to the same side of the vac diaphragm as the factory one.

the type with the third port I think is for the later emissions quipped cars, at certain driving conditions it retards the timing to reduce NOx emissions. It reduced max power output and economy, leaving it off (capping it) will just have the emissions the same as the early models. No harm will come from it, and frankly I think it may be questionable if it really helps emissions. Increasing fuel consumption to get slightly lower Parts Per Million of NOx may not result in less emissions over all.
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dlb
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Re: Distributor vacuum advance diaphragm adventures

Post by dlb »

Petros wrote: Thu Sep 15, 2022 6:22 pm the type with the third port I think is for the later emissions quipped cars, at certain driving conditions it retards the timing to reduce NOx emissions. It reduced max power output and economy, leaving it off (capping it) will just have the emissions the same as the early models. No harm will come from it, and frankly I think it may be questionable if it really helps emissions. Increasing fuel consumption to get slightly lower Parts Per Million of NOx may not result in less emissions over all.
Are you talking about the third port on the vac advance? Isn't it for high altitude compensation?
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