unbobfinch

I have a 2006 Cobalt LT 2.2 with a manual transmission. It has 240,000 miles. My son tried to start it the other morning and it wouldn't start. He came in and said he thought the starter was bad but I found that it was a low battery. I put a charger on it and it started right up. It ran fine for 3-4 days and then on Friday afternoon, my son was driving home from work and called me to say the check engine light came on. I asked if it was flashing. He said, "no." I asked how the car was running. He said, "fine." He drove it the rest of the way home without issue (15ish miles). Before I could get home and check the codes, he drove it to his friend's house that night. It started and ran fine over there but when he left to come home, the car wouldn't start. His friend pulled the code and it was P0300 generic misfire. The battery was also low again and they tried to jump it but it wouldn't start. I went over the next day and checked the spark plugs, pulled the same code, and tried to jump it without any luck. I had the car towed home. After charging the battery, it wouldn't hold a charge so I replaced it. I had already replaced the alternator maybe 3 months ago. I've now replaced the battery, spark plugs, coil pack, ICM, starter and crankshaft position sensor. I've checked all of the fuses. I've cleaned the g105 ground and have checked that I have ground & power to the ICM connector. I don't have a fuel pressure gauge but it sounds like the fuel pump comes on when I turn the key and I've push on the schrader valve and fuel squirts out. The engine will crank but no start. If it sits for a while, the first time you try to crank it almost acts like it's going to fire but after that it just cranks. I'm not a mechanic, just a hack hoping to get this car up and running a bit longer for my son. Anything else I can check or test? Thanks

oilcanhenry

I'd check the fuel pressure.If its nor proper, the injectors wont deliver fuel. 55 to 62 PSI is normal

unbobfinch

Thanks for the reply. That was my next thought and I ordered a fuel pressure gauge that is being delivered today. I appreciate you letting me know the normal expected range.

unbobfinch

I've checked the fuel pressure with a gauge and I'm getting 58 PSI when I turn the key on and when cranking. I've put an in-line spark light tester on it and it lights up on each of the cylinders. My next guess is the timing chain jumped and needs to be replaced?

unbobfinch

I've pulled the valve cover and the timing cover. The timing marks all line up with where they are supposed to be. Cylinder one is top dead center, crankshaft key is at 12:00, intake cam is at 2:00 and exhaust cam is at 10:00. I rotated the crankshaft clockwise to line up the timing marks. I realize the colored chain links won't line up exactly where they are supposed to be but when I rotated the crankshaft all of the colored links lined up one link off of the timing marks. So, it looks to me like the chain has not jumped and I don't see any broken guides. When I first removed the valve cover, the chain was tight between the cam gears. When I rotate the crankshaft, the chain will become loose between the cam gears and then will tighten up as the crankshaft key returns to the 12:00 position. Obviously with the number of miles on this car, the chain set should be replaced but is this the cause of the crank but no start?

unbobfinch

I went ahead and replaced the timing set (both chains, all the guides, gears, and both tensioners) and the water pump while I had it all apart. When I put it back together it didn't fire right up. It was still cranking but no start. A couple of times is kind of had a slight sputter like it wanted to fire up but never would. I let it sit for a few hours and then tried starting it again. I let it crank for a good long time and pumped on the gas and it finally fired up. Once it started up, it sounds great and is running and driving again. Ulitmately I think the problem was a bad coil pack and a bad timing chain tensioner.