Mechanics

4.3 HARD START HOT

2000 Chevrolet Blazer • 6 cylinder 4WD Automatic • 160,000 miles

2000 Blazer 4.3 Hard start hot. After sitting overnight it will start ok. After reaching operating temp, if you shut it off and attempt to start with in a few minutes or longer it is a prolonged crank. Ign coil was replaced. Tested fuel pressure with KOEO, 60 psi and then drops to about 55 psi after regulator opens. Fuel pressure when running or when problem occurs is aound 55 psi. I have found that the fuel pressure will bleed down after a short amount of time with the KOEO or key off. However when the problem occurs fuel pressure is ok. Tested with pedal to the floor "ecm clear out condition" when cranking, made no difference.
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Markgmurray
November 25, 2010.




My info says the pressure shouldn't drop more than 5 psi in 10 minutes. If drop is excessive, you can block off supply and return, one at a time, see if pressure holds. I forgot to look, if you have a return line?

JDL
Nov 25, 2010.
I will try restricting the return line and monitor pressure. Do you have any insight or info regarding why it woud start ok after sitting over night. Even when it is a hard start issue, fuel pressure is w/ in spec. Also if I shut it off and crank it again w/ in a few seconds it stats ok, but if it sits for more than 5-10 minutes or longer it becomesa hards start. Do you think the Ign module could cause this? The Ign coil has been replaced the cap/rotor has been checked. (Performed a tune up last year). I'm just not 100% sure on testing the Ign Module.

Tiny
Markgmurray
Nov 25, 2010.
Does the pressure drop faster than the spec listed. A hot restart issue could be caused by a flood issue?
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JDL
Nov 25, 2010.
With the key on engine off the pressure will quickly go to about 60 psi then drop quickly about 5 psi when the regulator opens (I'm assuming). After that the pressure will continue to drop to 0 psi with in a minute or two. It's odd that it if you shut it off for only a second or two and crank, it will start ok, but if you let it sit for 5 - 10 minutes or longer it becomes an issue. Also it starts ok if it sits overnight cold.

Thanks
-Mark

Tiny
Markgmurray
Nov 26, 2010.

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