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.

 

[Doubeleive]

keep it basic fuel-air-spark.
you know you have fuel, so that leaves air and spark
but you should confirm you have at least 50-65lbs fuel pressure with key on (when cold, before first start)

 

[DCT]

keep it basic fuel-air-spark.
you know you have fuel, so that leaves air and spark
but you should confirm you have at least 50-65lbs fuel pressure with key on (when cold, before first start)

Yes, fuel pressure confirmed.

Must be sensor somewhere. TB is clean. Intake boots ok. Maybe MAF doesn’t like cold. It’s the original.

 

[drakon543]

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.

dont need a tech 2 for the basics even with a live data scanner you can buy an innova from most advance auto parts stores under 100 bucks. they work well enough for anything ive ever had to mess with. as far as the sensor itself some vehicles have 1 sensor some have 2 im not sure on yours. your other temp sensor would be your intake air temperature sensor. sometimes they are part of the mass air for sensor. they can also just be a separate sensor somewhere else on the filter housing or the intake tube or even somewhere on the intake manifold. on your truck it appears to be a part of your mass air flow sensor. i suggest getting a can of maf specific cleaner from your local autoparts store. remove the maf and spray it down heavily. leave it inside the house to dry for atleast an hour before you attempt to reinstall and plug it back in. while your doing this unhook your battery to allow the ecm to clear its tables. when you go to start the truck up if it does start it might stall the first time or stumble. just let it stall or stumble restart if needed and let it relearn with a clean maf and it will smooth out on its own.

 

[Doubeleive]

Yes, fuel pressure confirmed.

Must be sensor somewhere. TB is clean. Intake boots ok. Maybe MAF doesn’t like cold. It’s the original.

When you cleaned the throttle body did you also clean the iac? (it is attached to the drivers side of the throttle body)

 

[DCT]

When you cleaned the throttle body did you also clean the iac? (it is attached to the drivers side of the throttle body)

Yes.

I haven't tried swapping out the MAF.

 

[jasonb100272]

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.

crank shaft sensor. Any auto store or rock auto . I would use a Delphi about 55 shipped. Google replacement. If you are fairly mechanical you can do it. This is comon especially if its a hit / miss starting problems but they can fail completely. But see if you hold the gas pedal down when starting if it starts faster? Then it could be a fuel or emissions problem. coil packs? Are there any codes? vapor canister purge valve. Good luck.

 

[DCT]

crank shaft sensor. Any auto store or rock auto . I would use a Delphi about 55 shipped. Google replacement. If you are fairly mechanical you can do it. This is comon especially if its a hit / miss starting problems but they can fail completely. But see if you hold the gas pedal down when starting if it starts faster? Then it could be a fuel or emissions problem. coil packs? Are there any codes? vapor canister purge valve. Good luck.

I’ll try the gas pedal. Spark and fuel are good. I will research the vapor canister. Thanks

 

[Jeff Shriner]

OK HERE IS A THOUGHT, HAVE A CAN OF STARTING FLUID READY FOR WHEN IT CRANKS AND DOES NOT START, WHEN IT HAPPENS GIVE IT A SQUIRT. THAT IS THE ONLY, REPEAT ONLY WAY TO KNOW THAT IT IS NOT FUEL RELATED IN ANY WAY. IF IT STILL DOES NOT START THAN YOU CAN MOVE TO SPARK BUT THERE IS VERY LITTLE IN THE WAY OF SENSORS OTHER THAN CAM / CRANK THAT CONTOLS SPARK. IF IT DOES START WHICH WOULD BE MY BET THAN YOU ARE STILL A WAYS FROM FIGURING THE PROBLEM OUT AND IT IS HONESTLY VERY UNLIKELY TO BE A SENSOR. I HAVE CHASED THESE ISSUES DOWN ON MULTIPLE BRANDS AND ALMOST ALWAYS ENDS UP AT A BAD CONNECTION OR BAD GROUND.

EITHER WAY THROWING PARTS AT IT WONT HELP IF YOU DONT KNOW THE DIRECTION TO GO.

OR SELL IT TO SOMEONE THAT LIVES IN ARIZONA LOL

 

[ScottieTooHottie]

I like the temp sensor diagnosis.

Turn the key to run and listen for the fuel pump to spin. Try that ten times. Better spin every time. Don't start the engine.

If the pump spins, check for spark at one spark plug. If no spark, my first guess is the camshaft position sensor at the top rear of the engine. But I think that one throws a code. On mine, the wiring to the connector on the harness was frayed just enough to let it start, but not always. Run to Autozone and borrow a scanner if you don't have one.

 

[Doubeleive]

temp sensor is extremely unlikely in my opinion