He means top dead center on compression and top dead center on exhaust. This is a term relative to cam position. Dowels up you are top dead center on compression on number one. Was there a question in that post? Depending on what you're doing it may not matter which tdc.

I guess I was more stressed out than I thought. Honestly don't remember typing the f word. Sorry

I know that, but don't the cam gears dictate which stroke phase it is? For example. If I did a timing belt, and I lined up all the marks, with the red marks on the cam gears on the inside. Then the first stroke is induction, but if I put the cam gears with the black marks on the inside, then it would be the exhaust stroke with injectors spraying fuel into closed intake valves. Correct or wrong?

This might be a stupid question. But does the 90 4g63 have a crank sensor?

Yes cam gears dictate which stroke it is. With crank sprocket on it's mark, and both cam sprockets dowel pins up (at 12:00 not 6:00), and cam marks lined up exactly opposite each other (exhaust at 3:00, intake at 9:00), then cyl 1 is at tdc between compression and power strokes (when spark plug fires). [When cam dowel pins are down (6:00), cyl 1 is at tdc but between exhaust and intake strokes].

wolf alchemy said:

This might be a stupid question. But does the 90 4g63 have a crank sensor?

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No. It has a CAS which supplies both tdc and crank angle signals. Only 2g's have CPS (and a different type of CAS).

That's exactly what I thought. Now what he said may apply to a single over head cam set up. Thank you for clearing that up for me.

Haha! But that all means I'm still stuck with no spark for no apparent reason....thanks every one.

All four stroke engines have intake, compression, ignition and exhaust. Doesnt matter one cam or two cams.

pauleyman said:

All four stroke engines have intake, compression, ignition and exhaust. Doesnt matter one cam or two cams.

Click to expand...

Yes I know that.....best way to explain it is. That the mechanic told me tdc of piston one has two setting. Combustion or compression, but that doesn't apply to these cars, because the crank doesn't determine that. The camshafts do. But if we took into account a single over head cam, then what he is saying is kinda correct. Because there's only one shaft operating all valves. So you could put the camshaf on upside down with the cam sensor upside down. That way 1st piston starts the opposite phase........this is resolved. My camshaft dowel pins were pointing straight up when I did the timing. Its all correct. You all helped me, and that mechanic is mixing our engine format with some other engine. End of story.

Single cam or multiple makes no difference. On a four stroke engine each piston reaches TDC twice in one cycle. That's what your "mechanic" was trying to explain.

You're correct in that it's the cam timing that determines which stroke of the cycle the cylinder is in when its piston is at TDC.

We imply TDC compression stroke when we say TDC.

Back to the problem.

To get spark the CAS need to tell the ECU where in the cycle it is.
The ECU has to work.
The ECU tells the Power Transistor to charge a coil.
The Coil has to have have power.
When the ECU turns off the Power Transistor the coil generated the high voltage needed to create a spark.

I believe you have tested the PTU and Coils. Have you checked at the Coil to PTU side of the ignition while turning the CAS to see the switching going on? At the PTU to ECU side?

That last paragragh to find out if my cas is working horribly confused me. Am I testing plugs, the parts?

The procedure is documented in threads here but you probe the two signal pins (perhaps at the ECU to get easy access to the signals) while the CAS is powered and someone turns it. You'll see the voltage swing from 0v to 5v as it is rotated.

How to test 1g CAS?

I have a possibly stupid question. If I did the timing, but put the cas on qmwith the fin spun 180°. Will it start if I remove it and set it correctly. Or will I have to rotate the engine, back to the correct tdc, then fix the cas?