2008 Aveo5 Delayed Start Overnight in Humid Weather

[drock]

Hi,

Video Here: https://www.youtube.com/watch?v=yhqchwIpeUQ . It finally starts at the end. That thumping you hear is my foot against the pedal.

Appreciate any help/insight on troubleshooting this issue. We recently moved to a house with a garage (we were in an apartment before). It is definitely more humid, and now the car is having trouble starting in the morning. Once it starts - it's fine for the day (even if it sits around for a few hours). The next morning though, it's the same issue.

It seems like the engine doesn't get compression, but finally does and starts (if I throttle the gas pedal). It's similar to when the fuel pump went, but I just changed that six months ago (with an AC Delco pump) and once it does start the first time - it's good for the day.

Things I've checked / replaced:
1. Used a multimeter on the battery, voltage is good and the voltage drop seems fine when starting (drops to ~11), so I think the CCAs are good. It was changed ~2 years ago
2. Checked a bunch of connections and wires (no bulges, no dielelectric grease interfering with connections, cleaned the battery contacts). Don't see any sparks in the dark while it tries to start (see video)
3. Replaced the fuel pump ~6 months ago, also I do hear the fuel pump start if I just have the ignition set to ON
4. General tune-up a year ago (plugs, wires, gasket, pcv valve)

Anyone have any ideas? I was thinking maybe the coil pack, but it "looks" fine (no dust on it), and once the engine starts - it runs perfectly (no misfires, etc.). This started happening the morning after we moved in.

There are no stored codes in the engine.

Thanks for your help!

[avguy]

What were the symptoms that caused you to replace the factory fuel pump?

If this latest problem happens consistently every morning, you can do some testing. Before trying to start it, spray a small amount of carb cleaner into the TB, and then try starting but keep your foot off the gas. If it doesn't fire at all, here's another thing you can try the following morning. Remove the spark plugs before any attempt to start. If they are wet, then you have a direction to diagnose further. But (more likely) if the plugs are dry and look ok, ground them one at a time and turn the engine over just enough to check the spark from each of them.

[drock]

What were the symptoms that caused you to replace the factory fuel pump?

If this latest problem happens consistently every morning, you can do some testing. Before trying to start it, spray a small amount of carb cleaner into the TB, and then try starting but keep your foot off the gas. If it doesn't fire at all, here's another thing you can try the following morning. Remove the spark plugs before any attempt to start. If they are wet, then you have a direction to diagnose further. But (more likely) if the plugs are dry and look ok, ground them one at a time and turn the engine over just enough to check the spark from each of them.

Hi - Thanks for your reply! Good thought on the throttle body. I replaced that about a year ago too (it was popping a code and wasn't running well), but haven't checked it recently, so I'll definitely look into that.

I changed the fuel pump out because of a no start in winter. It was pretty similar to this issue - except that it never would start. Had to have it towed to a garage (since I was street parked in NYC and couldn't really work on it).

[avguy]

Actually I wasn't talking about cleaning the TB (although that's never a bad thing either). It was a suggestion to see if it would fire on carb cleaner, which I prefer to use instead of starting fluid. The idea is to determine if its a fuel or spark issue, and move along from there.