My 99 Tahoe 4x4 won't start

[mario.jr]

Hey guys, i had been reading other posts and seen how you help each other out on problems with your vehicles and thought i should sign up. i drive a 1999 Chevy Tahoe 5.7l v8.
My Tahoe does not want to start. i have done a few things to it already such as replacing the spark plugs and wires, battery, starter, fuel filter, and fuel pump. It cranks over and sounds like it wants to start and will sometimes almost start but never does. if you have experienced this or have any ideas that will help it will be greatly appreciated! I already have already checked the Factory security system and it was not that.
Thank you for all and any help.

 

[lesterl]

Have you pulled any codes?

Unplug the MAF sensors electrical connector, see if it cranks then.

If it does you have a bad MAF sensor most likely.

What is fuel pressure?

Will it start right up with a shot of carb cleaner?

 

[mario.jr]

It already cranks but wont start. I'm going to check for codes today.

 

[Jimmytahoe]

Bet it's the ignition coil under the distributor cap, my 99 did the same thing and sure enough, that's what it was.

 

[mario.jr]

how much would that ignition coil cost?

 

[Jimmytahoe]

Less then $100

 

[lesterl]

Pickup coil is under the distributor cap, Ignition coil is mounted to the Passenger side of the intake....

 

[MO Viet Vet]

Do you have spark at the plugs when cranking? Basics. If was cranking, why the starter?

 

[mario.jr]

i have spark and the ignition coil good. i changed the distributor cap and rotor and all the wires are in the right order. still doesn't start. any other suggestions?

 

[lesterl]

Spark at the plugs I would try a shot of carb cleaner into the intake, if it fires up for a second, then try unplugging the MAF sensor electrical connector and repeat, also check fuel pressure-ESPECIALLY if you used a junk auto parts store pump instead of an AC Delco/ Delphi pump......

 

[remauto1187]

Is the spark bright blue or white or orange? If its anything other than bright blue then you have a ignition coil and/or ignition control module problem.

Then check fuel pressure. Is it up to spec? If not then you may have introduced a problem fuel pump into the mix OR the fuel pressure regulator which is under the upper intake manifold could be the culprit.

Next? let us know how these pan out first.

 

[lesterl]

Bump....

 

[mario.jr]

the shot of carb cleaner didn't work. what else could it be?????

 

[lesterl]

Did it try to start off with the carb cleaner? No- bad coil/ wires/ cap/ rotor. Yes- check fuel pressure, MAF helps with fueling also.....

 

[remauto1187]

the shot of carb cleaner didn't work. what else could it be?????

It could be alot of different things and you'll never narrow it down to the culprit until you stop guessing and/or throwing parts at it. Troubleshooting is an art it in itself which requires nothing more than being systematic.

Suck squeeze bang blow is all you need to remember which the 4 basic cycles of an engine.
Intake compression ignition exhaust in a gasoline engine and a jet engine too.
Hows that spark look? Is it bright blue? 5.7l distributor caps are notorious for needing to be replaced EVERY year especially using aftermarket ones. I have a 99 GMC Sierra with a 5.7l with 256k on it now and still running. I've gotten aftermarket caps that had tiny cracks in them and gave me the same symptoms that you have on yours. They also do the same thing when they get around a year old. Pop the cap off and see if its got a bunch of white carbon all over the terminals and mounded up. If it is, replace it preferably with a ac delco part.

 

[mario.jr]

the cap and rotor are brand new. i have 180k on my 5.7l ive tried disconnecting the maf sensor and it still didnt start. i tried the shot of carb cleaner and it still didnt start. it cranks and wants to start. it almost does but then just continues to crank.

 

[MO Viet Vet]

Try more than just a shot of carb cleaner and see if fires off. Fuel delivery problem then. When you say a "shot" is hard to determine how much.

 

[lesterl]

Yeah, a shot with a small engine, a 5.7l you need to kinda hose it down, then it will still start then die, almost need someone to crank it over while you shoot it in.

Unplugging the electrical connector on the MAF sensor disables the sensor in the PCM and it runs off the MAP sensor only (speed density). If the MAF is bad and not indicating enough airflow the PCM wont inject enough/ any fuel, unplugging it the PCM will "ignore" it....

P.S. I have a 1998 GMC Sierra now, sold my 95 Tahoe..... miss it....

 

[mario.jr]

the check engine light is on but it reads no codes!! could it be my ECM computer that is fried???

 

[lesterl]

Yeah, a shot with a small engine, a 5.7l you need to kinda hose it down, then it will still start then die, almost need someone to crank it over while you shoot it in.

Unplugging the electrical connector on the MAF sensor disables the sensor in the PCM and it runs off the MAP sensor only (speed density). If the MAF is bad and not indicating enough airflow the PCM wont inject enough/ any fuel, unplugging it the PCM will "ignore" it....

P.S. I have a 1998 GMC Sierra now, sold my 95 Tahoe..... miss it....