truck wont start. bad cat?

[lost in wyoming]

Ok here it is Iam helping a freind with his 97 gmc it brings up a low flow code an the cat #2 bank. ran real bad now wont start at all. will one bad cat couse it not to start? it has two

[z07]

A typical cat failure affects performance at the upper end of the power band first not idle and not starting. A strong sulfer exhaust smell, bogging down under load, and stutter under sudden throttle opening are the normal symptoms of a cat that is failing.

To remove the cats from the possible causes of the no start problem, remove (unplug and unbolt) the O2 sensors that are upstream (manifold side) of the cats. The open holes will releave any pressure problem if one exists.

I doubt the cats are causing a no start.

Check the normal things first.

Does the engine turn over at the normal speed when cranking?
Do you have spark at each plug?
Do you have fuel pressure?/Do you hear the fuel pump run when the key moves to run?
Do the injectors pulse?
Do you see any disconnected electrical connectors or vacuum lines?
Will a sample of fuel from the truck run a lawn mower ok?
Does the voltage from the battery drop below 10 volts durring cranking?

[lost in wyoming]

we pulled the cats it starts and runs but not very well.the owner drove it last night it quite three times. not pulling any codes. going to check fuil next

[leolkfrm]

Are you using a code reader or a scan tool? sounds like you need to read the sensors and anaylze the results

[lost in wyoming]

its a code reader

[mudseeker]

you really should find someone to put it on a scan tool. a sensor could be getting lazy and still not throw a code. i've seen it happen with an IAC valve before. i checked for codes with the scan tool and came up with nothing, but after digging deeper the scan tool finally found the problem.