98civicowner

Need some help saving my 98 civic ex coupe. About a week ago my civic was running fine, then one morning I went out to start the car for work and the car turned over but would not start. So the diagnostics started.

I initially thought I might not be getting fuel since I've been smelling fuel when I first start the car but originally thought this was just due to the engine running rich in the cold weather. So I ran a fuel system pressure test and found every thing was within spec Next started to check spark and found that there was no spark. First checked the ignition coil resistances. Primary resistance was high according to the Haynes manual but after buying a new one I found the new primary resistance matched exactly to the currently installed coil so the coil was never replaced. I next checked voltages within the distributor. Battery voltage was found coming into the distributor BLK/YEL wire and at the primary and at the + and - terminals of the coil when the key is in the on position. When cranking the engine the voltage at the coil primary drops to around 9.5 volts and fluctuates slightly between 9.3-9.6 volts. Also check shorts to ground from the rotor and from the PCM-IGN input signal and no shorts were apparent. Also checked for continuity from the ICM to the PCM and continuity exists. After all these checks I was sure the issue was the ignition control module so I had it tested at Autozone who told me it failed the test. After installing the replacement, along with a new rotor and distributor cap, I was disappointed to find out that nothing had changed and I still had no spark.

Other helpful information, Distributor is turning, CKP/TDC/CYP sensor resistances are within specification. Anyone have any ideas what else could be preventing the spark. My concern is it might be the PCM but there is no check engine light and no codes reported using an OBD scanner.

Former User

How do your coil resistance readings compare with those in the diagram below?

98civicowner

Its a TEC coil and reads 1.3 ohm and 13 kOhm however a brand new coil for the car read 1.3 ohm on the primary as well.

Also saw an earlier thread that spoke about the yellow/green wire coming from the ECU should be 10V with the car in the ON position. I have no voltage under this scenario. What if anything does that mean?

Former User

At what resistance/Ohm scale was your multimeter set when you made the A/B resistance measurement? It should be on the lowest scale. And when set to the lowest scale, what is the Ohm reading when the two multimeter probes are touched together?

How exactly did you do this voltage test? The voltage at the Yel/Grn wire comes from the ICM not the ECU. With the key in ON(II), what voltage do you measure on the Yel/Grn wire with all wires inside the distributor connected?

Are all wires inside the distributor plugged into/attached at the proper locations?

And do the Blk/Yel wire and Wht/Blu wire attached to the ICM have battery voltage with the key in ON(II):

98civicowner

The resistance/Ohm scale on the multimeter was set to 200 which is the lowest above the diode setting. The Ohm reading when the two multimeter probes are touched together fluctuates between .5 and .6 which brings the resistance within spec. Thanks for point that out.

Again thanks for clarifying the test I read in the other post as I misread the thread. After performing the test correctly as you indicated, the voltage at the ICM-ECU wire is 6.5V with the key in the ON position. This test was performed with all wires connected. Blk/Yel and Wht/Blu have battery voltage with the key in the ON position. Also, the ICM was replaced as part of this diagnostic after failing testing at autozone.

Former User

6.5V on the Yel/Grn wire seems low to me. I think it should be 10-12V. But I'm not sure this is the problem.

If the Yel/Grn wire does not have a short or open, then it may be time to try swapping a known good ECU into your car.

00CIVICSITEIN

Any updates on this? I'm actually having the same problem. Car ran great for two years, then all of a sudden it died.

xero_xero

have a tec coil off an obd0 b16 swap in a 1st gen crx. everything is tested, (compression, ground, icm, ecu, wiring, no spark, fuel, main relay)

tested .8ohm on A and B, 11.86kohm on A to Main

what toleraces are within spec?