My 99 yukon wont start when its cold, I can spray carb cleaner in the throttle body and it will fire,but other wise it wont start unless its warm.

Battery has full crank power?battery connection.

No start, no spark ? Spray, carefully, carb cleaner into throttle body to see if it is a fuel issue. The burst of carb cleaner should make it crank for a moment if it is lack of fuel. Wear safety glasses and keep a fire extinguisher nearby.

First thing I would check it the fuel pressure at the rail. You can spray some starting fluid or carb cleaner into throttle body. If it want to fire it is most likely the fuel pump. If it doesn't try to fire it is most likely ignition related. Good luck

Your model should be a throttle body injected engine.
So no float and no jets like a carb.
Have you checked fuel pressure before and after cranking ?
Are the injectors spraying fuel when you crank it ?
If not, do you have power and a ground signal for the injectors ?

You need spark at the right time, fuel pressure at the injectors, and normal compression.
Have the spark plugs been changed in the past couple of years ?
Have you checked the fuel pressure to see if it is enough ?
Have you sprayed carb cleaner into the throttle body to try to make the engine try to start ?
Does it sound like it has normal compression when cranking ?

Did you check the fuel pressure before you replaced the pump ?
Can you spray carb cleaner or starting fluid into the throttle body and make the engine want to start ?
If it is throttle body injected, can you see the fuel spray when you crank it hot ?

low compression or spark plugs need to be changed.

EATHER IS NOT GOOD , ITS FOR COLD COLD MOTORS.. CHECK YOUR FUEL PRESSURE AND GAS FILTER .YOU MIGHT HAVE A BAD FUEL PUMP ITS IN THE GAS TANK!!! . USE CARB & CHOKE CLEANER ..PARTS MASTER # 1736 ..ITS NOT AS HOT AND WONT POP A HEAD GASKET .IF'N I WAS ANY HELP AT ALL PLEASE VOTE.. JAY

severe vacuum leak possibly or IAC isn't functioning. Try cleaning throttle body and IAC with carb cleaner and see if it helps. Always be very careful with carb cleaner, if you have any spark leaking around plug wires you will have a engine fire on your hands also if engine backfires same thing. always install air cleaner before trying to start engine after spraying a bunch of carb cleaner down the throttle body.

It's the automatic choke!

The choke is "closed" or barely open... When cold, the engine needs a RICH mixture (more gasoline, less air). When the engine warms up, it requires a LEAN mixture (less gas, more air).

It is probably creating BLACK tailpipe smoke ... that means unburnt gasoline. (Blue smoke is OIL, white smoke is WATER).

Put the parking / emergency brake ON.
1. Remove air cleaner assembly from intake, use a carb cleaner spray or throttle body spray cleaner and spray just a little. (AutoZone $5)
2. Find the accelerator arm under the hood.
3. start car, rev the engine to make sure how to operate the accelerator from under the hood.
4. Carefully spray into carb / throttle body and work the accelerator ... don't let the engine die...
5. Watch out for "backfire"... it may create a small flame out of the carb. It will extinguish itself in one second.

6. You may need to do this two, three times.
7. Add a "complete fuel system cleaner" to your next tank of gas ($8).

That's it! ... pretty cheap, too.

Hope this helps!