2000 bonneville engine cranks over but will not start when cold

The fuel pressure regulator has a check valve in it ti keep up fuel pressure when the engine is not running. There is a test port on the regulator to connect a fuel pressure test gauge.

Watch the temp gauge when the electric radiator fans come on. The temp sensor that controls when the fan comes on may be faulty.

Have you checked your battery? Does the dashboard light up?
Check your fuses first, then check your battery. Check that the battery is connected properly. A loosely-connected battery is usually the cause of a car not cranking at all.

Sounds like the fuel pump one way valve is bad.
The pump has a valve that is supposed to hold fuel pressure when the engine is off.
Could also be a problem with the fuel pump relay.
I would check fuel pressure before and after you crank the engine.
It should be around 25-35psi before and higher after you crank it.

My 2000 Bonneville did the exact same thing. It's the mass flow air sensor I'm almost 100% sure this is what your problem is.

First thing to do is replace you fuel filter, If there is a check engine light have the code read, Most parts store will do this for free. Get the code number type that into google for further advise.

Check the egr valve by located it and the vacuum hose connected to it. pull of the hose and check it for wear like cracks or hardening of the rubber. If it looks ok, reconnect it to the egr and start the engine while it is cold and with the engine idling, remove the hose from egr valve. If the engine sputters and then dies, pull off the vacuum hose one more time and try to start the car. If it runs fine with the hose disconnected, replace the egr valve.

not always a diy and due to possibe dangers not recommended

check the crank sensor. this is a very common failure on these vehicles. hope this info helps!

you need to get it scaned.auto zone will do it for free but most of the time it a o2 sensor or coolant sensor