Where to begin, two weeks ago i had the same problem as I do now. I checked the oil and cleaned the air filter. I didn't disconnect anything or unplug anything. I go to start it and the motor cranks, but does not start. I replugged in connectors around the intake, gave it a little throttle while starting it, checked fuses and tried several times to start it. But it would not start. After 20 minutes of trying, what "fixed it" was removing the pcv return to the intake, it started right up. I plugged in the pcv and not problems. That was two weeks ago and about 400 miles with no problems until last night.

Last night I go to start the car, and the same problem as before. It cranks, but doesn't start. I checked the fuses again, moved relays to different positions to see if the problem moves, unplugged the pcv again, released the pressure in the gas intake rails, checked plug wires, and still nothing.

What i can tell you is the fuel pump turns on, the starter works, the battery is good, fuses and relays good, good fuel that I know of, plugs replaced 3000 miles ago, other than routine maintenance nothing has been replaced swapped installed or moved in two years. My thoughts of what it could be are MAF or intake sensor problems or something with fuel.

Other than that, I have no idea and I need to get it home, any ideas or help is appreciated.

 

this is a stretch, do you have a k&n, did you reoil the filter? maybe the maf got soaked, usually just makes it idle high and run ruff but might cause the no start.

 

i di clean it, but afterwards i cleaned the maf. im thinking it is a fuel issue and will change the fuel filter tomorrow. hopefully thats it

 

Might get better responses on LS1 Engine Tech forum. Do you want me to move it there?

 

I would just test the simple things first. Engine needs air, fuel and spark to run. Put a spark plug tester on a wire and have someone crank it to see if you are getting spark. If you are getting spark then I would check fuel. I hate spending money on parts if not fixing the problem. Check the spark before you take time to replace fuel filter. Spark tester is only a couple of bucks in the auto parts store. Good luck. Let us know what you find. Good luck. I have been chasing a miss fire issue and think I just found the source of problem. Only took me 2 months of on and off testing.

 

Well, i changed the fuel filter, got allot better fuel pressure according to spray out of the fuel rail. Checked and cleaned all the connectors fuses and relays in the engine bay except for the PCM, reset the PCM, tested the MAF, throttle body sensor, throttle body air sensor and temp sensor, and still it wont run. It seems that if I leave it overnight, it will start right up. If I dont let it warm up, turn it off, then restart it soon after, it wont start and the whole process starts over. Im confident its not fuel pressure or the pump. Maybe injectors clogged, but all of them? I will check the ignition next and see what happens.

 

I'd check the fuel pressure, just in case. My car had the same symptoms, except it's an LT1, and it was the fuel pump.

 

I'm no expert by a long shot but someone told me that if you aren't getting 40 psi of fuel pressure then your not going anywhere. Maybe your fuel pump is on it's way out. I would get you a tester and hook it up to the shrader valve on the fuel rail and see what you have.

 

Ok, solved the problem. the easy answer was spark plugs. Heres the full story. Last year, I saw a bulletin that GM put out (2003) about new standards for spark plugs for LS1 motors. It said to use ACDelco iridium ones that are pregapped at something like 0.04 when the original recommended gap was 0.06. So i I paid the $60 dollars for these 100000 mile spark plugs.

Last night I pulled the drivers side plugs and two were good, two were a little oily, but not bad. So I bought some NGK copper plugs, gapped them to 0.06, and installed only 4 on the drivers side. I worked all day to get the car started and it wouldn't, I replaced only 4 plugs and it started right away. I put in all new plugs and it runs like a champ.

My theory is the small gap over time with a little bit use doesn't ignite like a bigger gap does. I think that when the iridium ones are warmed up, no problems, but when they are cold, it is harder for them to spark when they have been used. With the iridium ones, the car ran very well with no sputtering or loss in MPG, it just wouldn't start. Ive never had a problem with the standard gapping and copper plugs so will stick with these.

 

The LS1 fuel system runs at 58psi.

 

Yah, sorry mine is a lt1. Like I said, no expert.