2001 Suburban - cold start problem

[DCT]

Need help please. I searched the forums but no luck.

When the weather is below 50 degrees, engine will keep cranking but not start. This happens only in the winter. The rest of the year the motor runs perfect.

After about 10 tries, the motor will finally turn over and start. Once the motor is warm, it will re-start no problem.

Engine is a 5.3L, 300k miles, but has a new starter, 3 year old fuel pump, new intake manifold gaskets, new plugs and wires, and new air filter. No mods to the engine, all stock.

No vacuum leaks, I changed all vacuum hoses. Catalytic converters and O2 sensors all good, I just passed smog check. I checked fuel pressure, no leak down overnight, and pressure is good during start up in the cold weather.

I don't know what else to check or replace. Thanks for the help and suggestions.

 

[Fless]

Are you running gas, not some mix of E85?

More details on your rig, please.

 

[DCT]

Gas. 87 octane. No E85.

 

[drakon543]

im not 100% with the whats and where's but it sounds like you a a temp sensor sending incorrect values to the ecm. ecm isnt seeing the correct temperature somewhere so its not making the correction for cold weather start. if the temperature sensor is sending values within spec but wrong it wont show a fault but can still cause problems. so anyway im not sure where your intake air temperature is but that could be a problem with that. also you are going to have 1 or 2 engine temperature. if you have 2 the one is dedicated to sending temperature readings to the ecm. your best option is to use an advanced scanner of some kind that can do live data readings. it will tell you what your intake air temperature reading is showing. with the truck cold the reading should be close to whatever the current ambient temperature is. if you have 2 engine temperature you should be able to see 2 different readings for your engine temperature shown. again with engine cold if the readings are far off from each other that sensor is faulty. probably an ohm reading you can pull off the sensors but im not sure what the reading should be.

 

[DCT]

Thanks. Other than the coolant temp sensor, where are the other sensors? I want to replace if not too expensive.

 

[Doubeleive]

I am just guessing here but I would check to see if you have spark and I would check it on that first try when it is cold in the morning, it could be a harness connector is not making good contact when it is cold, corrosion or something, which brings me to the battery cables I would definitely pull the cables off and give them a clean up (wire brush) and re attach just to see if it makes any difference.

 

[DCT]

I was thinking ignition too. I checked and replaced all those things.

Strange thing is I searched regional forums with colder weather year round and no luck. I figured it would a more common problem for them.

I called GM shops and no one has heard of this starting issue. Last resort will be the dealership, which I want to avoid.

 

[George B]

I was thinking ignition too. I checked and replaced all those things.

Strange thing is I searched regional forums with colder weather year round and no luck. I figured it would a more common problem for them.

I called GM shops and no one has heard of this starting issue. Last resort will be the dealership, which I want to avoid.

You should be able to avoid the dealership. Some of the troubleshooting would be easier with a Tech2 but there are ways.

You replaced ignition parts but have you physically confirmed there is spark? Confirmed fuel pressure and injector pulse? Confirm what temperature the ECM thinks the engine is. This is based on the sensor in the head on the drivers side near the front I believe. Make sure the throttle body is clean and able to open easily. Make sure all your intake manifold bolts are snug.

 

[drakon543]

Thanks. Other than the coolant temp sensor, where are the other sensors? I want to replace if not too expensive.

woah killer im no gm guru just making a suggestion on what the problem could be. throwing parts at a problem is just wasting money and an advanced scanner to do what i suggested really isnt too expensive. i know your probably dieing to get it fixed at this point but getting some other opinions and doing some diagnostics would help. if your still just going to throw the parts at it i wouldn't be able to help you with the where's anyway. I just know it can happen so im just trying to pass some suggestions along.

 

[DCT]

Unfortunately I don’t have access to a Tech2.

Are you talking about the coolant temp sensor? If so, I replaced recently with an AC Delco.