For a little while I had noticed that my civic would very intermittently have a long crank time. This bothered me since it was so rare. It did this like once or twice every few months. Lately it started to get more consistent.

I needed to know if this was a fuel or spark issue. I have a fuel pressure gauge mounted right near the fuel injectors- and I started literally opening the hood every time I would crank it to check fuel pressure when I cycled the key- and it showed good every time. I started thinking it was spark.

I then started bringing my little hand-held scope with me everywhere I went. When I started the car- I would open the hood and inductively measure the current draw on the feed wire going to the coil inside of the distributor. This way I would be able to check and see if the coil was trying to produce spark, and obviously if the inputs to the PCM were right allowing it to be triggered by the ignition module...



Good photo showing coil control and current draw

Finally - one day I had caught it after about a month of trying. I cranked the car and it didn't want to start and I saw first hand that I did not get coil control consistently. I immediately pulled a wiring schematic with the input wires coming from the distributor, so I could measure these. For this- I need to use my 4 channel laptop scope (picoscope 4425)



Here you can see the connections at the distributor. There are 3 pickups inside of the distributor. they all make thier own voltage by passing a magnet near a coil of wire.

Here is the 4 channel scope. This is a picture of the car running with the suspect distributor. The 4 traces are as follows: blue: CKP sensor red: TDC sensor green: 720 of crank / 360 of cam gold: coil control current ramp

Here is a picture of my setup.

The problem I was having was that as soon as I connected my test setup- the problem went away. I waited another day and let it completely cool off.

The next day or so I was totally able to re-create the long crank on the 4 channel scope. I could see that I was missing the gold pulse most of the time. The CKP signal was really week (like less than 2 volts range!). The 720 and tdc were not that great either.

Here is get intermittent coil control. Look how weak the ckp (blue) is especially.

I was then confident to take apart the distributor. I wanted to make sure nothing was funky inside before I ordered a new distributor.

Everything looked OK. I had this apart a few years ago when I was planning to replace the seal. I wanted to make sure the pickups had not moved.







I replaced the distributor and checked/set the timing. The car starts right after you turn the key every time now. When I measured the new voltage- I am getting about a 5 volt range during cranking on the ckp. The car started so fast that I couldn't really get regular cranking scope pictures to compare- so I disabled the fuel injection by pulling the fuse out so it would not start.




Here you can see how quickly it starts. In fact the voltage jumps so high on the ckp when it starts running that I went past the 10V scale.

 

Excellent post showing your troubleshooting method. Thanks for sharing!