DarkFlame

We replaced the bad distributor on my '98 Civic LX, and it started right up. We went to the trouble of setting the engine at TDC before removing the bad unit, & it was still there when I installed the new distributor.

As a point of reference, the distributor has a drive shaft with tabs on it that fit into slots on the end of the camshaft, resulting in a 1:1 rotation ratio - wherever the camshaft is, that's where the distributor is. To make it foolproof, the tabs on the distributor drive shaft are off-center, making it impossible to fit the distributor tabs even 1 degree off the camshaft slots, and definitely not 180 degrees.

So, if the distributor drive shaft only fits into the camshaft one way, what difference does it make for the engine to be at 0 degrees TDC? Won't it work just fine, as long as the tabs fit the slots?

Jakester9500

Yes. I've never cared about TDC when just pulling the distributor and never witnessed ill effects from doing so.

24TEN

iTrader: (2)

You pretty much answered your own question with the second paragraph.

B serious

iTrader: (1)

You don't need the engine at TDC to install the distributor. But it's nice to have the rotor slot at a finite position before installing.

Its not IMPOSSIBLE to install it 180° off. I've bought a few "non running" cars that had it upside down and forced on. One of them had a cracked distributor mount as a result, and the other had a cracked distrubutor rotor driver.

One of them, however, had the rotor driver 180° off and the previous owner then took the rotor and also placed it 180° off...which cancelled each other out. The car ran fine till I got a hold of it and put the distributor on correctly after removing it to perform another repair. I had no idea the rotor was on backwards. I was chasing ghosts till I took the cap off, put the engine at TDC and saw the rotor was pointing at the #4 cylinder. Pure fu#&ing insanity.

DarkFlame

I was thinking I had it 180° off. I knew the tabs were off-center, so that should prevent me from getting the distributor 180° off. But, I had left the old one exactly in the same position as when I pulled it out, and it was 180° off from where I had to put the new one. I tried both of them again and found that they both easily fit only the same way. I figured that was a sign.

I thought about how far off the tolerance would have to be to allow both tabs to adequately fit backwards. And, if it were that loose but still installed correctly, the amount of play would have provided an added noise, and it makes me wonder how far off the ignition could have been wandering, coughing, & sputtering. That would be a worn camshaft.

Let me note this critical point. I said "they both only fit the same way." When I turned each distributor 180°, I could get one tab to fit into one slot, and the bolt attachment nearest that tab would appear to flush up. However, the other tab would only start to go into the slot, and that amount of off-kilter is enough to make a forceful attempt to attach in that position result in something breaking. The instructions that came with the new distributor even said not to force it into place by using the bolts to pull it flush. I merely tried it both ways by hand, found one way it flushed up easily, but not so much the other way. So, I chose the easy way.

THEN, I reconnected the plug and the battery connections, sat in the driver's seat and turned the key. ...

It fired one cylinder and then just turned over. I won't say it even was cranking because the rhythm was different from before.

I started this installation with all the spark plugs in place, each of the wires attached at both ends, the plug and the original distributor cap. We had removed any wires from the distributor during the troubleshooting process, so they were still in original position, I thought. I did not mark them at any time. When I moved the wires from the old cap to the new one, I moved them one at a time, making sure it went onto the same position as the one from which it was removed. But, I figured something in the wiring was wrong.

I got online & found a diagram & interpreted what it was telling me, and the wires on the distributor were apparently wrong. So, I swapped them out to match the drawing. That didn't work. I went back online & looked at another drawing and that had another diagram for which cylinders went to which points on the distributor. So, I switched the wires, and that time the car started.

I wish I had marked the wires on the original distributor - it would be nice to know if I had it right the 1st time. Oh, well. It works, and that's the important thing.

Now that I re-read what you wrote, the first diagram I found showed the distributor off by 90°. The 2nd one showed it correctly.

B serious

iTrader: (1)

Yep. So basically the reason for putting it at TDC is to use the rotor position as a double check. If you have to force it on, it's a good sign that it's 180° off. Some aftermarket rotor drivers and worn parts have more slop. So 180° off position goes from force fit to marginal tight fit....which uninitiated people may not notice.

So if you set the motor to TDC with the cam marks pointed at each other, you can put the distributor on and then remove the cap to check that the rotor is pointing at cyl 1's prong position.

B serious

iTrader: (1)

Not necessary for function. But a good double check procedure.