Brandon Dawson

First off, I've read several posts about this same thing but they all seem slightly different or were solved using methods that aren't working for me.
Car: 2000 Honda Civic EX.

Last year my car started doing this thing where it wouldn't start when it was hot outside. It was super annoying and caused some problems but summer was almost over and the problem ended up going away and I happily forgot about it. Fast forward to a month ago. I'm in AZ and things started heating up. My car was not only refusing to start when it was hot outside but it was also dying while I was driving. The engine would die and electrical would shut off. The electrical came back on almost instantaneously but the engine wouldn't start for 10-15 seconds. I take the care to my mechanic and he replaced the ignition switch. The car no longer dies when I'm driving. However, it still wouldn't start when it was hot outside. I research a bunch and talk with my mechanic and we both think it's the main relay so we replaced the main relay.

A few days later the car is parked outside all afternoon while I'm in a meeting and when I come out it won't start. This has happened a few more times. Reading online I decide to clean the G101 (which already looked really clean) but that hasn't helped. From what I'm seeing online few people have said the ECU or even the vapor lock and I don't know where to go. Heck, as far as I know it could be the wire from the main relay to the fuel pump.

Recap, new ignition switch, main relay, and clean G101 ground. Thoughts?

Nedrobmas

On the next hot day, get in the car and rock it back and forth or shake it from the outside then try to start it.

Brandon Dawson

So it has been sitting in front of my house for several hours now (to purposely cause the problem) and it isn't starting, even though it is getting nice out now as night is coming. I just went out, and shook it as hard as I could (great stress reliever) and still nothing.

Nedrobmas

Questionnaire
Fuel pump and spark plugs, When did you last change your spark plugs? Did you get gas from the places you normally get gas from? Does it come on when it's cooler? Do your car make a sound when you turn the key to on before you start it?
Check all the fuses for broken links and corrosion.

Also, what is it doing, does it crank but won't turn over?

Oh yea, battery voltage?

Brandon Dawson

Nedrobmas

Why was the fuel pump changed? What does the spark plugs look like is what I meant to say, is the tip rounded or flat? If its still flat, check the gap size. You said the battery checked good, what you mean by that?

I would check the battery voltage when its cold & hot when its not starting with a multi-meter. In thinking it could be the stator going bad, ecu, alternator, something electrical or fuel pressure related.

NVturbo

coil ignitor inside the distributor

civicservice

Similar symptoms for me on the same vintage - it turned out to be a dirty IAC. Here's how to diagnose it. When the car won't start, press the accelerator. If the car starts then dies when you release the accelerator, you may have a dirty IAC. A similar test would be to disconnect the brake booster hose and start. Either test will bypass the IAC. Cleaning the IAC and throttle body fixed the problem.

If the car doesn't start with accelerator down or brake booster pulled, it's probably not IAC.

collkid

Absolutely the main rely.