Distributor Igniter different for manual vs auto trans?

[Mark]

My wagon wouldn't start this morning and eventually I narrowed it down to a bad distributor. I replaced it with one out of my '81 Tercel and now the wagon's fine, but I want to try repairing its original distributor. While it was still on the car, I did a bunch of the tests from the FSM and the coil resistances were good and there was voltage where it should be so I'm guessing it's the igniter. According to the FSM and parts places like Rock Auto, the igniter is internally different for manual and auto trans Tercels. Does anyone have any idea why? Is it an RPM thing (autos idle slightly higher)? Is there any reason why I can't use a manual igniter in an auto trans distributor?

[Petros]

I have never heard of that, I have swapped whole distributors around from one car to another without any issues (even across engine series from other model cars). perhaps there is a slightly different spark advance curve in the auto trans, though I do not know why that would affect the igniter. might be a different part number for some reason, or perhaps a different supplier for auto trans cars. As long as it will mount properly I see no reason it should not work. It is a simple device, it sends a pulse to the coil so it fires at the right time. If it mounts the same, not likely it would make any difference. I have seen a toyota truck where someone adapted an igniter from another car to work, he made a mount and ran clearly non-factory wiring. Perhaps he had an igntier from another car and needed one for his truck, so make it work.

[Mark]

The tests in the FSM say there are different results for resistance/voltage in the distributor between the manual trans and other tercels. The ignitor is just a solid-state switch that acts as the old points in the old-style distributor. The ignitor switch stays open for a certain amount of time like the amount of time the gap in the points stays open (dwell angle). Maybe the manual trans had a different dwell angle? It doesn't make sense to me. I've swapped several distributors between different Tercels (1st and 2nd gen) and they all worked fine, but they were all automatics. On rock auto, the manual ignitor is about half the price of the automatic one even with different brands. I'd rather spend $11 for the manual ignitor instead of $30-something for the auto one if it will work fine.

[Mark]

I wonder if it has to do with the tachometer. I've never seen an automatic with one in the dash. There is a connection coming off the distributor for checking engine speed for maintenance, but it's not normally connected to anything during normal driving. Adding a permanent tachometer to the system may interfere with the millivolt pulse from the pickup coil.

[Petros]

you can put a tach on the auto trans tercels without issue, all the tach does is count pulses, it should work with either one. In fact you can buy aftermarket tachs that work in many different cars, that just need a signal wire.

I suspect it might have to do with who supplied the parts, they may have used different production lines for auto trans and manual trans, perhaps different factories, with different parts suppliers.

I can not imagine what would be different as far as signal requirements, the igniter and spark plug do not know the difference if it is auto trans or manual, it just sparks at the right time. I can see them matching the cam timing and spark advance (and even carb jetting) to better work with the torque requirements for the auto trans vs. manual trans, but that would not affect the igniter signal nor spark plug demands.

[Mark]

So I did the FSM tests on the igniter today when I had it out of the distributor and it behaved as it's supposed to. I re-did the tests on the coils and they still passed. All the tests still showed that there was nothing wrong with it. I took the distributor apart and cleaned it all up (there was some dust and oil residue inside) and cleaned/lubed the centrifugal advance system. I put it all back together and put it back in the wagon and it now works fine. Strange. I guess I don't have to worry about getting a new igniter after all.

[Mark]

Another thought about why an igniter might be different for manual vs auto transmissions is that the Tercel auto is only a 3-speed. On the highway, the engine rpm is much higher than on a standard trans Tercel (5-speed?). At these high speeds, the amount of time that the igniter is allowing current to charge the coil might not be enough to fully charge the coil and give a good spark. Maybe on the auto this electronic dwell angle is set differently to allow the coil to charge more fully at high speeds.

[Mark]

So I did the FSM tests on the igniter today when I had it out of the distributor and it behaved as it's supposed to. I re-did the tests on the coils and they still passed. All the tests still showed that there was nothing wrong with it. I took the distributor apart and cleaned it all up (there was some dust and oil residue inside) and cleaned/lubed the centrifugal advance system. I put it all back together and put it back in the wagon and it now works fine. Strange. I guess I don't have to worry about getting a new igniter after all.

So I said it worked fine, but it would actually take about 2-3 seconds of cranking before it would start. I've never had that happen before on any of my cars. They usually start within maybe 1/2 second or one rotation of the crankshaft. 2 days ago, it wouldn't start again (no spark). It was a cooler, rainy day and I wondered if it was the distributor cap. I replaced the cap with one from a good distributor, but there was no change. I noticed that the old rotor had some play in both directions. I replaced the cap and rotor with an old set I had laying around and now it starts up again immediately. So I guess the problem wasn't the coils/igniter, but a bad rotor and cap.

[rer233]

Had a similar problem years ago with my '84 SR5- turned out to be a bad coil (mine was inside the dizzy.) Car would only screw up on cold damp days. I too changed the cap & rotor, and it seemed to be better for a while, but the problem never really went away 'till I changed the coil.

Good Luck!

[Mark]

Did you do the resistance check on the coil? Mine passed according to the FSM, but I've heard that a coil could still be bad when exposed to high voltages and the test (using a multi meter) might not show this. Just wondering how definitive the FSM resistance test is.

[rer233]

I didn't check resistance on mine- only had a problem in the wet, so I figured the insulation was breaking down.

[Petros]

I have found on other cars that all of the components may pass the resistance test when cold, but still be bad when warm. On our mazda it has two igniters, a main and a back up. we kept getting CEL signal that igniter was bad, but when I bench test it passed (the manual specifically instructed to test it cold). Since it only gave code when on hot days, I decided to run it until hot and than test it again (as quickly as I could get to it anyway after a long up hill hot run). sure enough, it failed when it was warm.

I would expect the same problem with any electrical component. Try them both cold and after they are warmed up, see what readings you get.

[Mark]

This morning was probably the coldest morning I've felt so far this year (about 7 degrees Celsius) and I tried to start the wagon and it started up immediately. This reassured me a bit that the distributor is now fine and it was a cap/rotor issue (maybe saying this out loud is bad luck). I looked back at my maintenance log and the last time I changed the cap/rotor on that vehicle was in 2012, so about 4+ years. The contacts in the cap were crusted over with white deposits and as I mentioned the rotor had play in both directions when installed on the shaft.