I have a 2000 Mustang and I have had this problem for about a month now. When it is a hot day outside, the car will crank but work start. On a cloudy day, in the morning, and at night the car starts up fine. I have had both the fuel pump and fuel filter replaced after this and it was fine for about a week and now its doing it again. Someone I talked to said something about Vapor Lock ? Please Help me out ASAP.

 

it could also be a radiator problem. im sure you woulda noticed if it was leaking or not but is the coolant clean and is there enough in there because i had the same problem with my 96. turned out my coolant was brown

 

I don't think vapour lock happens on injected cars,, the pressure's too high.

your problem sounds ignition related to me

 

You can vapor lock a fuel injected car due to the fuel tank vent being clogged.See if the car will start with the fuel filler cap off.This will cause a Check Engine Soon light but it will give you a clue as to what to look at.You can reset the light by removing one of the battery terminals for a few minutes.

 

any other things it could be ?

 

When it happens again see if you can find your fuel line. If you can find a spot (after the pump, I am not that familiar with newer mustangs so I don't know where the pump is) that you can remove. If gas doesn't immediately flow out you may have vapor lock or something clogging your line(make sure you keep the gas from getting on your paint job). If there is gas that comes out then let someone crank the engine over for a small amount of time (5 - 10 seconds) and see if fuel comes out in a steady flow. I would actually have it flow into a clear empty (clean) bottle so you can see if the gas is clear or cloudy. If it's clear then you are fine. If it's cloudy, you may want to drain your tank and put in a fresh supply of gas from a good gas station such as Chevron or Texaco. That's my idea anyway..... Has the car been sitting for any amount of time at all before you started having this problem? Another thing, when you replaced your fuel filter did you blow through it to check how easy the flow is?

 

Those are the worst answers Ive ever heard.Sorry.ITS NOT VAPERLOCKED........Is the car sparking??????I bet its the ignition.How would a radiator keep a car from starting????How would it bevaperlocked and then not cause its cloudy or dark???????Pull off a spark plug wire and stick a screwdriver in it and hold it near metal and see if the spark jumps.Oviously do this when its not starting.start there bet you'll find your problem

 

How does cloudy or dark effect the ignition coils?

 

This is the weirdest thing Ive ever heard!!!!!!!!!!!!!!!!What does that have to do with anything??????????Please dont answer tech ?s when you dont know the answers