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No spark on 2 cylinders

No spark on 2 cylinders

Postby Paulwilliamson8230 [OP] » May 04 2021, 12:38am

Hi everyone, new to the forum hopefully someone here can offer some insight,advice or confirm my worst fear. Im the proud owner of a 2002 silverado 2500hd, the truck ended up spinning a rod at about 230k so i recently opted to buy a rebuilt motor thru orileys. Four grand and a couple of days later new engine arrived, between work and bad weather I managed to get the old engine out and the new one in within a couple of weeks. Last Sunday was the moment i had been waiting on for what seemed like forever, the day i plug in the last of the wires and fire up my new motor. I get in,take a deep breath and turn the key (after cranking motor with fuel pump relay removed until i seen oil pressure) motor spins no start eventually i get i few chugs and a sputter or two, after much of the same results the motor finally “runs” only like pure garbage. I have to have the pedal to the floor it wont idle or rev over 1k. So i break out the scanner and check codes, i see im getting a p0336 (crank sensor circuit a out of range). I reused old crank sensor so I figured thats the cause, i make a dead run last min to parts store get a new one slap it in, same results same code. Its late on a Sunday and i have to work early so i end up calling it a day. The next day i look into wiring, thinking maybe a bad or missing ground , i run continuity checks and resistance checks to the grounds on the back of the cyl head and the main ground behind the power steering pump all look good. I check for voltage at crank sensor harness im getting 12v w key on. Just to be safe i replace my cam sensor also and check for any pinched, chafed,damaged or burnt wires and find nothing. At this point i try to start it again and it seems to be doing better but still wont hold idle wont rev over 3k now and runs so rough it shook like an earth quake but seemed to smooth out slightly at higher rpm. I dont run it like this long, i pull all the plugs to check them, these are all new plugs so reading them should be easy. When i pull them i find the plugs for cylinders 5,7,4,6 look brand new still aside from a bit of white residue I assume was gas, the other plugs you could tell were involved in combustion but very black like running a rich condition. At this point i hook all plugs back into the wires and crank the motor with them out so i can check for spark, well all have spark except for cylinders 4 and 7, nothing not even a weak spark. Now im down to checking coils, i do this by plugging the harness from a coil i knew was fireing into one that wasn’t and like magic i have fire on that coil. So i now know coils are good I start checking the harness for the 2 cylinders not fireing both have good ground and good 12v, i trace wires back as far as i can close to pcm its the red/black wire for cyl 7 and the green/white for cyl 4 referred to in all the pinouts as ignition control wire. I see no damage and since i have no idea what to test for on thes wires i run a continuity test,passed and check ohms, low resistance. I returned and replaced crank sensor with new on same results same p0336 code. After pulling out most of my hair i realize the last link in this puzzle is that damn reluctor wheel. I decided to check it out so i go to harbor freight and pick up one of them digital inspection scopes i snake the camera down in the hole and get a somewhat blurry but workable image of the reluctor. I have my assistant turn motor by hand all looked pretty uniform until this one part (ill include pictures) it didn’t look smooth like the rest it looked rough almost broken, once again this is on a 50$ inspection camera kinda blurry and hard to make out but it is visibly different. Has anyone ever heard of a rebuilt engine having a broken reluctor? Dont they test these before they send them out? I dont even understand how something like that could break the way its sheathed in the rear main cap unless it was broken when they put it together. Its very frustrating considering im already about 8k into this swap plus weeks of time and busted knuckles. I really hope its the pcm at this point but something tells me im not that lucky. Here are some pics of the reluctor as best I could get, ive spun it around multiple times and this is the only spot that is un uniform and looks this way. What do yall think



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Original Poster
Posts: 1
Topics: 1
Joined: May 02 2021, 10:46pm
Location: Texas
Year: 2002
Make/Model: Chevrolet Silverado
Variant: LT
Extra Info: Hd 2500 8.1
Group Membership:
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