Need assistance!

Hey everyone,
I've run out of ideas. I need assistance in finding a solution to my engine failures. The engine is from a 03 Yukon 1500 XL 5.3l l59 (flex fuel). I've had the engine running for about 10 minutes in the past and it was rough. Now it will only start now and then, 3 minute top. Just look for some HELP!
Alien

[@UCanDoIt2Mike]

So I think you are on the right track with some of your diagnosis. Not based on experience, but based on basic troubleshooting skills, I offer the following. Your timing set appears to be in order. I could not see the Dot on the Crank sprocket, but the Cam sprocket is in position and the Piston appears to be at top, so I think you are good there. The Number one spark plug which appears that it has not fired appears to be the biggest indicator (and non-discolored of the headers) that you have a SPARK, or FUEL issue. There is an electrical testing device that you can put between (inline) the Spark Plug and the Coil that will light up every time it fires. That device would help check for spark. I know you did a Fuel Injector Bench test, but I cannot remember if that was with the Real Harness. That test did ensure that all of your Injectors are in good order. You need to make sure that the number 1 cylinder injector is firing (providing fuel). Could be a power (12v+) issue or a Ground (-) issue. Should be able to disconnect the injector terminal and test the ground wire. Just a few thoughts! Mike

[@AlienRestoMod]

You're like the Jedi master of diagnosing LS1 5.3l . The frustration level was high earlier today but see the path through your wisdom. Thank you.👽

[@CalebsHobbies]

Agreed. Old fashioned spark test will tell you if fuel or power. Put ground everywhere at least temporarily to eliminate that and check connections to #1. I've run into fake spark plugs off Ebay which caused all sorts of headaches. Good luck! Narrow it down and simplify so you don't go crazy. Keep us updated.

[@billsalzman]

Sorry Tim , I'm a painter and Fabricator. I wish I knew more about the mechanical side. It is alien 2 me. good luck

[@HsPerformanceWi]

​A simple test light will do to check for injector pulse, connect the clamp to battery positive and test the ground side of the injector connector while cranking. Also, pull a plug on the bank in question and physically check for spark there. my guess is you missed or have a poor engine ground on the harness. Good luck and thanks for the sub!

[@AlienRestoMod]

Thanks for the tips, I will look into the ground for the harness.👽

[@kelvinbattjes5206]

Have you checked the codes from the obd 2? That will give you some direction of where to look.

[@vetteman1542]

What J Cook said, also check the grounds for both the coils and injectors, you might have to temp jump to ground to eliminate possibilities, just make dang sure its a ground wire you are jumping.

[@AlienRestoMod]

Adding to the list. Thank you. 👽

[@wilsworkshop]

Add more grounds if you only have 1 or 2. A good thick ground wire from heads to block, heads to frame, block to frame. You can't have too many grounds with a LS motor. I usually have around 4 between the main engine parts and the frame/battery. Won't hurt to check fuel pressure also, should be near 58 psi / 4 bar. Since at least 3 cylinders are firing it's likely not computer/timing related, but wiring/fuel delivery related.

[@AlienRestoMod]

I will add more grounds. Funny thing, I'm working on lowering the PSI from 58 to 50. The engine I have is rated at 48-50 PSI . 03 Yukon 5.3l l59. It was suggested to me by Auto Zone dude. I looked it up and that's what the manufacturer recommends for this engine. So I'm putting together a setup to test this theory. If you see a new video from in the next 24 hrs, it worked.👽

[@VinylVillageGarage]

Have checked injector pulse? I heard you say you have battery voltage with key on but what about the ground pulse from the ecm on the poor preforming cylinders. Use a noid light or modified led so as not to damage the driver in the ecm if it is good

[@AlienRestoMod]

It's on the list of checks, need to rent the noid light from AutoZone. 👽

[@sgtbehrens]

i would try the old school pull a plug with it attached to the spark plug wire, video the process and turn the engine over. review the footage to see if the spark plug is firing. I would do that to all 5 cylinders where you are having issues. If you dont see spark, start running the wire back and backtrack from there to see where the issue is. Can u smell Fuel in those cylinders? if you can smell fuel and no spark, def en electrical issue.

[@AlienRestoMod]

I will check that out, thanks for the input and pointing me in the right direction.👽

[@greggkuzila7513]

You need to check all your grounds

[@robbys67rs]

Could the coil harnesses be flip flopped?

[@AlienRestoMod]

I will put it on the list to checkout. 👽

[@jcook69camaro]

check your firing order of the injectors and coils.

[@AlienRestoMod]

Thank you, I will roger that .👽

[@billsalzman]

Hmmm science.

[@cliffjamerson3107]

Maybe message Richard holder