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Cold Start problem

jferrell

By jferrell
in Ask A GM Technician

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jferrell Enthusiast

jferrell

Posted
Posted

2002 silverado 1500 with 5.3 gas engine

Problem: doesn't want to start in cold weather - intermittent but colder is worse

New Parts so far: Fuel Pump, Fuel Pressure Regulator and Air filter.

Parts checked and cleaned: Fuel Pump Relay, all fuses, OBD pending codes, IAC valve, throttle body.

Fuel pressure readings (two tests in 40 degree weather, listed in order):

cold before starting: 54 and 57 PSI

running: 49 and 52

shutoff: 48 both times

5 minutes after shutoff: climbed from 48 to 58 and stayed both times

retested with gas cap on and off - no change

After starting: runs like a champ at all times.

Owner: frustrated.

royg Enthusiast

royg

Posted
Posted

That's some pretty incosistant readings. Does the fuel pressure hold when you shut it off, or does it drop? Did you check the fuel filter?

jferrell Enthusiast

jferrell

Posted
  • Author
Posted

I forgot to mention the new fuel filter - that's been updated in the post. Notice in the post that when shut off, there is a slight drop to 48 (normal by my shop manual) and then it creeps UP to 58 and stays. The book has you looking for a steady state or a drop of no more than 5 PSI over 5 minutes. I don't know what happens overnight, as I've not left the guage on. When I attach the guage, I of course relieve the pressure first.

95Sierra2500 Senior Enthusiast

95Sierra2500

Posted
Posted

I'd still suggest that those fuel pressures are low. Most times when I encounter a hard start issue with newer vehicles, anything less than 55psi and it's a pain to start...more than that and it starts with no issues.

cstahl New Member

cstahl

Posted
Posted
Is there another likely cause for low pressure in cold termperature? I want to try it all before I go after the pump.

Had a similar problem on a Sierra 1500. The symptom was hard starting, but if the key was turned on for 10 to 15 seconds before activating the starter, it started easier. Once it started, it ran great.

 

Changed the fuel pump, filter, and wires at different shops. Then the fourth try was the fuel regulator (mounted on top of the engine, drivers side). After $400, turned out to be a $20 part.

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