Rep Power: 0

My '02 Civic suddenly wouldn't start the other morning. It cranks strong. I have spark on all four cylinders. I can hear the fuel pump and smell fuel after trying to start, so I believe it is getting fuel. All pass from the computer. Sensor outputs all look reasonable except for the O2 sensors that are both reading 1.275 volts, even with both sensors unplugged. Is this 1.275 V reading the normal pre-start state for these O2 sensors, or does indicate something to look further into?

 
Rep Power: 211

o2 issue shouldn't prevent it from starting unless possibly a clogged catalytic converter. Could be a flooded fuel situation? Try starting it with gas pedal fully depressed as that will disable the fuel injectors and allow maximum air into the cylinders.

If that doesn't work try starter spray or TB cleaner in the throttle body while starting.
How did you determine it's getting spark on all cylinders?

 
Rep Power: 0

I tested spark with my spark tester. Remove each coil from each plug one at a time, connect to spark tester, ground spark tester, turn engine over and observe spark in tester. It jumps the 30k Volt gap, so the spark is there and is as strong as it ought to be.

Will try some starter fluid.

 
Rep Power: 224

If you verify fuel and spark the next step would be compression and timing.

 
Rep Power: 211

Any update?

 
Rep Power: 0

Sorry, weather and work have been a bit unconducive for tinkering on the car. Haven't had a good chance to test it.

 
Rep Power: 0

Well, now I am confused. I sprayed a good amount of starter fluid into the intake and it started. I let it idle, figuring it would burn up the starter fluid and then stall, but it kept idling for a good 5 to 10 minutes, while I rounded up my scanner, hooked it up, and played around. O2 sensors were still unplugged, so I got O2 heater ckt codes, and the O2 sensors were still reading 1.3 V. Plugged the O2 sensors back in and the O2 sensor voltages dropped to 0. At this point, it is idling smooth, as if it was completely unaware of its stubbornness of the last week or so.

After idling several minutes, I shut it off, then immediately restarted it. It started easily.

So, now, I guess I wait a while and try starting it again later and see if it starts or not.

One way or another, I am confused. I generally don't believe cars fix themselves, but....

 
Rep Power: 223

Intermittent electrical issues are the hardest to diagnose. Checked batt voltage with the engine running and off?

 
Rep Power: 211

If it starts and runs normally in the coming days you can likely chalk it up to fuel flooded cylinders. Did you ever try starting it with the gas pedal fully depressed as I mentioned a few replies ago?

 
Rep Power: 0

So far, it is starting and running fine. I guess we'll chalk it up to flooded cylinders. I did not try starting with the pedal to the floor, but I also would have expected too much gas in the cylinders to dissipate over a day or too rather than a week or two.

Thanks to all for the interest and the help.

 
Rep Power: 211

Some flood situations can be difficult to solve. Pedal fully depressed is the first place to start. From there it can involve fixes such starter fluid, removing spark plugs and blowing compressed air into the cylinders and/or plugs removed and cranking the engine using the compression to blow the fuel out of the cylinders (engine sneeze..lol). Past that adding a an ounce oil into the cylinder, install plugs and crank. The oil will increase compression to help ignition.

Could be a possibility of worn fuel injector O-ring(s) causing a leak into the cylinder(s). However, unless the issue comes back soon that may not be a concern. Here's a read https://www.injectorrx.com/fuel-inje...uel-injectors/