Hard Starting Z71

NelBosco · June 23, 2005

Recently started experiencing a hard start condition. It does not matter if it is a cold start or hot restart. The engine cranks but does not fire on the first attempt no matter how long I crank but will immediately start on the second try like it always did. I have changed the fuel pressure regulator because I have access to GM parts. I have scanned for codes but none are stored and all values are normal. I read the TSB about clogged injectors and freeting corosion but I am not experiencing the rough or unstable idle. Pulled all the plugs and they all look normal and the same. Question is if I connect a fuel gauge to the rail and turn on the key but do not start what should the pressure be? And how long should it hold that pressure? I suspect I am not priming or holding fuel pressure. When running fuel pressure is 55psi and when I pull the vacuum hose it goes to 62 psi.

Thanks.

GM-Tech · June 23, 2005

Your pressure sounds good. What you need to look at is how long it holds pressure after the pump stops running. If it drops to 0 right away, the check valve in the pump is probably bad, which means you need a new pump.

Here's part of the diagnostic steps that check this...

After the fuel pump stops operating, the fuel pressure should stabilize, then remain constant.

Monitor the fuel pressure gage for 1 minute.

Does the fuel pressure drop more than the specified value?

34 kPa

(5 psi)

Go to Step 9

Go to Step 5

5

Relieve the fuel pressure to the first specified value.

Monitor the fuel pressure gage for 5 minutes.

Does the fuel pressure drop more than the second specified value?

69 kPa

(10 psi)

14 kPa

(2 psi)

Go to Step 24 (replace fuel pump)

Go to Step 6

NelBosco · September 15, 2005

This is an update to my hard starting:

My fuel pressure would not hold. It dropped to 0 psi as soon as the pump stopped priming. After running through the procedures I eliminated the regulator and fuel injectors. Last thing left was the fuel pump. I called my dealer and asked if he could give me the dealer discount on a new pump and I would install it since I was just out of warranty on mileage. To my astonishment they agreed to replace the pump under warranty.