92 Full-size Blazer.. 5.7 350 rough start and backfire
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Joined: Aug 2020
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92 Full-size Blazer.. 5.7 350 rough start and backfire
ok… I have a 92 Full size Blazer, 5.7 350. My son and I are rebuilding it and have replaced the motor with a crate engine from Summit. Obviously new wires, plugs, distributor and cap. Rebuilt injection system and new injectors.
ISSUE: When we turn it over it acts like it wants to start REALLY ROUGH and then back fires through throttle body. I know it has to be a timing issue… Could I have missed something when installing distributor? Is the timing just that far off? We put distributor on before we stabbed motor, set at top dead center on #1, i turned the cam gear to install distributor to line up number 1 cylinder (or i felt really close), I have checked all wires and tested spugs at distributor and have a spark on all. At a loss, any ideas would be appreciated!
Thanks, Roy
ISSUE: When we turn it over it acts like it wants to start REALLY ROUGH and then back fires through throttle body. I know it has to be a timing issue… Could I have missed something when installing distributor? Is the timing just that far off? We put distributor on before we stabbed motor, set at top dead center on #1, i turned the cam gear to install distributor to line up number 1 cylinder (or i felt really close), I have checked all wires and tested spugs at distributor and have a spark on all. At a loss, any ideas would be appreciated!
Thanks, Roy
CF Monarch
Joined: Jul 2011
Posts: 5,920
Likes: 140
From: kevinkpk
ok… I have a 92 Full size Blazer, 5.7 350. My son and I are rebuilding it and have replaced the motor with a crate engine from Summit. Obviously new wires, plugs, distributor and cap. Rebuilt injection system and new injectors.
ISSUE: When we turn it over it acts like it wants to start REALLY ROUGH and then back fires through throttle body. I know it has to be a timing issue… Could I have missed something when installing distributor? Is the timing just that far off? We put distributor on before we stabbed motor, set at top dead center on #1, i turned the cam gear to install distributor to line up number 1 cylinder (or i felt really close), I have checked all wires and tested spugs at distributor and have a spark on all. At a loss, any ideas would be appreciated!
Thanks, Roy
ISSUE: When we turn it over it acts like it wants to start REALLY ROUGH and then back fires through throttle body. I know it has to be a timing issue… Could I have missed something when installing distributor? Is the timing just that far off? We put distributor on before we stabbed motor, set at top dead center on #1, i turned the cam gear to install distributor to line up number 1 cylinder (or i felt really close), I have checked all wires and tested spugs at distributor and have a spark on all. At a loss, any ideas would be appreciated!
Thanks, Roy
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CF Beginner
Joined: Aug 2020
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Yes sir on the wires order, pulled all wires and rerouted when I checked for spark. Will reinstall distributor at top dead again to verify that tomorrow. Thank you and if you think of anything else I appreciate the assist.
CF Active Member
Joined: Sep 2020
Posts: 220
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From: Raleigh, North Carolina
OPTIONSSTEP 1: CHECK ENGINE LIGHT
Anytime you have an engine that is backfiring the first thing to look for is a check engine light. If no warning lights are on continue down this guide. If the check engine or service engine soon light in on scan the computer for trouble codes. This will help locate the system that is having a problem and needs repair.
STEP 2: CHECKING FUEL SYSTEM PRESSURE
An intake back-fire explosion can be caused by the fuel air mixture being to lean when the engine is demanding power. Every internal combustion engine runs on a mixture of 14 to 1 which is fourteen parts air to one part fuel. Proper fuel pressure is needed to atomize the fuel correctly when it leaves the fuel injector to complete the burn process.
The most common cause for this problem is a weak fuel pump which cannot supply the volume of fuel needed for the injectors to produce a proper spray pattern or deliver the amount of fuel needed for engine acceleration. The fuel system pressure must be tested to see if the fuel delivery system is the problem.
Anytime you have an engine that is backfiring the first thing to look for is a check engine light. If no warning lights are on continue down this guide. If the check engine or service engine soon light in on scan the computer for trouble codes. This will help locate the system that is having a problem and needs repair.
STEP 2: CHECKING FUEL SYSTEM PRESSURE
An intake back-fire explosion can be caused by the fuel air mixture being to lean when the engine is demanding power. Every internal combustion engine runs on a mixture of 14 to 1 which is fourteen parts air to one part fuel. Proper fuel pressure is needed to atomize the fuel correctly when it leaves the fuel injector to complete the burn process.
The most common cause for this problem is a weak fuel pump which cannot supply the volume of fuel needed for the injectors to produce a proper spray pattern or deliver the amount of fuel needed for engine acceleration. The fuel system pressure must be tested to see if the fuel delivery system is the problem.
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