Thread: 2003 GT Won't Start when Engine is Warm...have to wait 45 min

Hey guys I am a member on ls1gto.com so I know all about searching for things before I post. I searched for this problem but came up with threads where the person's problem was slightly different. So I ended up making this thread to better describe my mom's Grand Prix and her problem.

2003 GT 90,000 miles

Her problem as she describes to me is that The car will cold start fine and the engine runs fine while driving around.

However, When the engine has reached normal temperature and then she shuts it off, about 80% of the time (started off as once and a while, but has progressively become worse the past 6 months) she can not get the car to start again.

The car will crank (aka the battery is fine) but it will not turn over. or sometimes it will turn over but sputter and then die right away and giving the engine gas has no effect on helping the engine stay running while it sputters...

She usually has to wait 45 min to an hour before it will start again. So she can drive her car to the grocery store, mall, gym etc and be fine but if she is only making a quick errand or one that will be under 45 min she always has to keep her car running while she is in the store...

I do not know too much about the 3.8 engine, but its pretty obvious her problem has something to do with the car not being able to start when the engine is "hot" aka normal operating temp.

Any ideas as to what could be the problem? Her check engine light hasn't come on. I dont think its the fuel filter because I wouldnt think that has to do with heat, and if it was the MAF a code would throw the check engine light on.

sorry for the long post.

Shawn

Sounds to me like your problem is vapor lock. Most likely caused by low residual fuel system pressure from a leaky fuel injector, fuel pump or fuel regulator.

Keeping your gas tank full until the problem is fixed might help. Good luck

thanks for the quick responses guys. can anyone (briefly) explain to me why it would cold start fine but then when the engine is warm it doesnt?

I just had the same problem, My car would shut off after 10 min, I had a faulty Mass airflow sensor. I had no SES light, ran fine while cool

Originally Posted by LS2 GTO

thanks for the quick responses guys. can anyone (briefly) explain to me why it would cold start fine but then when the engine is warm it doesnt?

Liquids under pressure tend to boil at higher temperatures. This is why both the coolant and fuel systems of a car benefit from being pressurized. I don’t have the exact numbers, but I’ll throw out some estimates for you. Gasoline can boil at temperatures as low as120-140F at atmospheric pressure. The same gasoline under pressure, lets say about 30 psig, might not boil until about 300F. As you can imagine the under hood temperatures of a “warmed up” car can easily get to 140F, and I don’t imagine fuel injectors were designed to spray a vapor. Your car is designed to maintain pressure in the fuel system even after it is shut down. I personally believe your car is not maintaining this residual fuel pressure for some reason.

Another tip that might help you get by, until you can have the car repaired, is fill up on gasoline without ethanol it.

where is the fuel pump located? I know on my camaro it was actually inside the fuel tank...

I'm surprised that nobody has suggested the fuel pump resistor yet? Did they not put them on the 2003?