Suburban 5.7L cold start problem

[gorent]

I have a 99 Suburban 5.7L that does not like to start when outside air temperature drops in the fall. This only effects initial morning start and once started it starts and runs fine all day! If i give it a very small shot of either in crankcase vent opening in intake bonnet it starts and runs fine after that! The pump cycles and seems to be fine! Once started all is fine untill the next morning after it sets 12 hours! Could it be the AIT switch?

[jdl]

Use a gage and check fuel pressure, first thing in the morning, key on, engine off. 60--66 psi. If you have the spider fuel system, that system is noted for problems.

[gorent]

I do have the poppet injector system! Is the electric system replacement better?

[MT-2500]

Originally Posted by gorent

I do have the poppet injector system! Is the electric system replacement better?

They are both electronic/electric.
But you have to have fuel fuel pressure to squirt any electric injector.

Like 65 lbs on yours.
Post back your cold key on and cold cranking fuel pressure.

[j cAT]

Originally Posted by gorent

I have a 99 Suburban 5.7L that does not like to start when outside air temperature drops in the fall. This only effects initial morning start and once started it starts and runs fine all day! If i give it a very small shot of either in crankcase vent opening in intake bonnet it starts and runs fine after that! The pump cycles and seems to be fine! Once started all is fine untill the next morning after it sets 12 hours! Could it be the AIT switch?

because this has been going on for years now I would guess it is the Engine coolant temp sensor. ECT is what I would check/replace.many have had this cause a poor cold start in the cold weather. the fuel pump check is good idea also , as when it gets colder the fuel demand is higher on first cold start. the ect reporting a warmer than actual temp will cause the injectors not to open long enough to get the engine running . ect is cheap and easy job.

[gorent]

Engine will not start at all cold without a shot of either! It will then run fine unless it sets for over a few hours. I replaced the fuel pressure regulator and fuel filter with no differance in starting! When I put pressure guage on it only will go to 50# with key on and 58# after running and warmed up with engine shut down! Pressure drop over 1/2 hour is less than 1/2 pound! This has an Airtex pump put in in 2007. I am thinking it is the pump? If poppets were leaking I should smell gas or gas in oil, which I do not and if gas was in cylinder it should not need either? Any thoughts on this? Naturally I have 44 gallon of gas in tank now!

[j cAT]

Originally Posted by gorent

Engine will not start at all cold without a shot of either! It will then run fine unless it sets for over a few hours. I replaced the fuel pressure regulator and fuel filter with no differance in starting! When I put pressure guage on it only will go to 50# with key on and 58# after running and warmed up with engine shut down! Pressure drop over 1/2 hour is less than 1/2 pound! This has an Airtex pump put in in 2007. I am thinking it is the pump? If poppets were leaking I should smell gas or gas in oil, which I do not and if gas was in cylinder it should not need either? Any thoughts on this? Naturally I have 44 gallon of gas in tank now!

Well the fuel pressure is too low. airtex pump lasting this long you lucked out.

with 44 gallons of fuel in the tank why so much ? that is a lot of weight to haul around. with a tank that large I would keep it at 1/2 .

now you must siphon out the fuel. I would use a 5 gallon container . then put the fuel in another vehicle. each gallon weighs about 8lbs.

take out 35 gallons then drop tank. more if posiible.
key on engine off 60-65psi. 50psi is no go.

[gorent]

Thank you! I will try to run tank down before I pull tank! At 11 miles to a gallon that does not take long. It is hard to siphon this vehicle with all the restrictions in the fill pipe! Which pump is the better : AC-Delco or Delphi ???

[777stickman]

I would go with the AC-Delco matched to your VIN. Go to the site below and send them your VIN. They'll give the correct part # and then you can check the price.

http://www.gmpartsdirect.com/

[j cAT]

Originally Posted by gorent

Thank you! I will try to run tank down before I pull tank! At 11 miles to a gallon that does not take long. It is hard to siphon this vehicle with all the restrictions in the fill pipe! Which pump is the better : AC-Delco or Delphi ???

most here have used the delphi. not saying its better than ac pump. cost is also a factor on why delphi seems to be the choice.

if you to slice in some new connectors , make sure the wires are soldered and sealed with heat shrink to protect from damage.

replace the fuel pump relay.