Screwed up when I replaced my Tstat/water pump?

[ColJessip]

The water pump went out a few weeks back. I replaced it and the T-stat following the "standard protocol."

Anyway, I've noticed the car takes longer to start when the engine is at operating temperature. In the morning/after work it starts immediately after turning the key. If I'm only gone for a few minutes, the car needs to be cranked for a good 7 seconds. I didn't notice this before the water pump issue, so it leads me to believe they are related.

[theholycow]

Which car?

[ColJessip]

That would be helpful . The GTO

[theholycow]

Coolant temperature sensor seems likely. I can't say that I understand why the CTS causes starting problems, but I know that GM V8s with a bad CTS won't start even with sufficient fuel pressure and such.

If you hadn't just done things with the cooling system I would have used this prioritized list:

1. Fuel pressure bleeding back into tank while vehicle is off. Try priming by turning key to "On" for a couple seconds (listen for fuel pump to run and stop), 3 times in a row, before starting. Confirm with fuel pressure gauge. First suspect is fuel pump check valve, but fuel pressure regulator is easier. After that, stuck-open injector or leaking fitting/tube.

2. Check spark

3. Check fuel again, try spraying some gas or starting fluid in throttle body before cranking, try (if easy) removing a fuel injector and see if it sprays while cranking

4. Coolant temperature sensor

5. Crankshaft position sensor (like the CTS, I don't fully understand why this prevents starting but it does)

6. Aftermarket anti-theft. GM's OEM anti-theft allows it to fire up but then makes it stall immediately, if false-alarmed from a malfunction, so that wouldn't be it.

7. Throttle position sensor; if it's providing false WOT signal then computer engages flood clear mode

...eh, like 5 edits later, I realized that some of those wouldn't be useful for this problem where it starts dependably after extended cranking...

[ColJessip]

I think it is a combo. When I let the fuel pump go for a few seconds before cranking, it cranks much faster. I guess the CTS is also causing problems though, as it still starts slower than when the engine is "cool."

[MustangFan424]

Don't go replacing things. Just drive it the way it is. If there is a problem, eventually it will show itself and throw a CEL. When you get the CEL you go from there. To throw parts at things for something thats not even a problem is just dumb. Don't waste your money.

[watkins]

Not every problem will cause a CEL, and not every CEL DTC is a real problem.

[theholycow]

I would think that "If I'm only gone for a few minutes, the car needs to be cranked for a good 7 seconds" qualifies as a problem showing itself.