Cold Start/Warm Start Problem

**I'mLS1John** · 02-22-2007, 05:42 PM

Hello everyone. I'm new and haven't got to post anything in the new member forum yet but will. I have a 98 TransAM that I bought in 2001. It only has 22,000 miles and is kept in the garage and is never driven in bad weather. Runs like an LS1 should until lately. Went to start it and it turns over fine but won't fire. I crank on it for about five seconds at a time and then let off the key and try again. May have to do this 12 or 15 times and then it may start. Once it starts it doesn't miss a lick. Took it out and drove the you know what out of it, triple digits no problem, no misses, no sputters. Put fresh gas in it, no help. It runs at normal operating temperature. You can shut it off for about 3 or 4 minutes and then it may do the same thing again. So at first I thought it was a cold start problem but now I know it does it when the engine is at normal operating temps.

I haven't got to try any old school tricks yet as far as trouble shooting goes but has anyone had a problem similar to this? Sounds to me like some kind of sensor problem, or maybe something in the computer not sending a right signal. It's got the power antenna so when I hit the key the antenna goes up and I can't tell for sure if the fuel pump is energizing or not so I'm going to pull the fuse on it next time I try. Could it be a coolant sensor gone bad? I changed the coolant for the first time in December 2006 although it looked fine it was past time. Don't want to get shafted at the dealer, any help is appreciated. Thanks

**juiced99ws6** · 02-22-2007, 05:54 PM

is your car throwing any codes.. I was thinking fuel while I wasreading that.. you would be able to shut off your radio and have the antenna not go up so that you can listen for the pump. is your gas cap on tight? maybe a pressure problem..

**YoMommasTA** · 02-22-2007, 06:47 PM

1st thing is check fuel pressure BEFORE you start it,put the gauge on the fuel rail and record the reading.Then turn the key on without starting the car and record the reading.Then watch the gauge and see what the pressure does with the key off.Next try starting the car and watch the gauge.Cold after sitting a few hrs the pressure will be low,After turning the key on the pressure should go to 55+and hold while the key is off.Cranking the pressure should be 55+ and stay there after it starts.Start with this test before you do anything else.One more thing before you do this test replace the fuel filter and see if that solves your troubles before chasing your tail.

**I'mLS1John** · 02-22-2007, 07:43 PM

Originally Posted by juiced99ws6

is your car throwing any codes.. I was thinking fuel while I wasreading that.. you would be able to shut off your radio and have the antenna not go up so that you can listen for the pump. is your gas cap on tight? maybe a pressure problem..

Forgot to mention, it's not throwing any codes. I thought antenna went up whether radio was on or not??? I think cap is ok, may be a pressure problem. Thanks!

**Red4Mula** · 02-22-2007, 07:47 PM

Originally Posted by I'mLS1John

Hello everyone. I'm new and haven't got to post anything in the new member forum yet but will. I have a 98 TransAM that I bought in 2001. It only has 22,000 miles and is kept in the garage and is never driven in bad weather. Runs like an LS1 should until lately. Went to start it and it turns over fine but won't fire. I crank on it for about five seconds at a time and then let off the key and try again. May have to do this 12 or 15 times and then it may start. Once it starts it doesn't miss a lick. Took it out and drove the you know what out of it, triple digits no problem, no misses, no sputters. Put fresh gas in it, no help. It runs at normal operating temperature. You can shut it off for about 3 or 4 minutes and then it may do the same thing again. So at first I thought it was a cold start problem but now I know it does it when the engine is at normal operating temps.

I haven't got to try any old school tricks yet as far as trouble shooting goes but has anyone had a problem similar to this? Sounds to me like some kind of sensor problem, or maybe something in the computer not sending a right signal. It's got the power antenna so when I hit the key the antenna goes up and I can't tell for sure if the fuel pump is energizing or not so I'm going to pull the fuse on it next time I try. Could it be a coolant sensor gone bad? I changed the coolant for the first time in December 2006 although it looked fine it was past time. Don't want to get shafted at the dealer, any help is appreciated. Thanks

I have the same problem, only when my car finally starts in the morning, it will easily turn back on when I turn it off.. So mines most likely a fuel pressure problem.. My coolant sensor is also

bad for sure, because my coolant light stays on even though my radiator and rsvr is full..

**I'mLS1John** · 02-22-2007, 07:51 PM

Originally Posted by YoMommasTA

1st thing is check fuel pressure BEFORE you start it,put the gauge on the fuel rail and record the reading.Then turn the key on without starting the car and record the reading.Then watch the gauge and see what the pressure does with the key off.Next try starting the car and watch the gauge.Cold after sitting a few hrs the pressure will be low,After turning the key on the pressure should go to 55+and hold while the key is off.Cranking the pressure should be 55+ and stay there after it starts.Start with this test before you do anything else.One more thing before you do this test replace the fuel filter and see if that solves your troubles before chasing your tail.

Thanks for the ideas. Where can you get a fuel pressure gauge to do the type of testing you are describing? Once it starts it runs like the scalded dog it always has. Would a stopped up filter maybe keep it from starting and then once it did start the fuel pump would provide the correct pressure? (it probably has never been changed). Thanks

**I'mLS1John** · 02-22-2007, 07:56 PM

Originally Posted by Red4Mula

I have the same problem, only when my car finally starts in the morning, it will easily turn back on when I turn it off.. So mines most likely a fuel pressure problem.. My coolant sensor is also

bad for sure, because my coolant light stays on even though my radiator and rsvr is full..

Thanks, maybe my coolant sensor is OK, my light is not on, no codes at all. BSounds like a pressure problem from what everyone is saying. Thanks again

**z28punk** · 02-22-2007, 09:08 PM

is it hesitating at all when it first starts up?

**0rion** · 02-22-2007, 10:08 PM

Originally Posted by YoMommasTA

1st thing is check fuel pressure BEFORE you start it,put the gauge on the fuel rail and record the reading.Then turn the key on without starting the car and record the reading.Then watch the gauge and see what the pressure does with the key off.Next try starting the car and watch the gauge.Cold after sitting a few hrs the pressure will be low,After turning the key on the pressure should go to 55+and hold while the key is off.Cranking the pressure should be 55+ and stay there after it starts.Start with this test before you do anything else.One more thing before you do this test replace the fuel filter and see if that solves your troubles before chasing your tail.

excellent advice

You can get a pressure gauge at pretty much any parts store for ~$20.

**YoMommasTA** · 02-23-2007, 07:04 AM

ty ,i would also be wary of the fuel pump relay.it could have bad contacts and would make the car act like this.But until you do some testing lets not assume anything.

**I'mLS1John** · 02-23-2007, 07:09 PM

Originally Posted by z28punk

is it hesitating at all when it first starts up?

No, it runs smooth once it starts. Never misses a lick.

**I'mLS1John** · 02-23-2007, 07:11 PM

Originally Posted by YoMommasTA

ty ,i would also be wary of the fuel pump relay.it could have bad contacts and would make the car act like this.But until you do some testing lets not assume anything.

Thanks, i'll check that too