Rebuilt engine wont run. Has compression, Spark and fuel?

[blades11b]

Hey guys. Hoping to get some help on an issue I am having with an engine I built. I build engines and do performance work for a living and have never came accross something this bizare. Here is the story.

Vehicle 2012 GMC Yukon 5.3 LC9 Flex Fuel

Came in making terrible noise, customer bought it off auction and it appeared it lost oil pressure. Tore it down and noticed someone had blocked off the oil ports for the DOD/AFM, put a new oil pump in it and replaced the lifters. At this point im only speculating but im assuming they did that and then sold it.

I proceeded to rebuild the engine with a new crank because it wiped the number 1 main out pretty bad, new bearings, new pistons punched out a little bigger heads redone etc. Put it together and put it back in the truck.

The problem is that it just wont run. Sometimes it will run for approx 1 second and die. Ive made modifications to my tune file that should get it to kick off but nothing I do seems to be helping.

Here is another weird note, when I was trouble shooting it for spark I had one plug removed and grounded out so I could verify it had spark, had someone turn it over and it started. Obviously sounded like crap with compression shooting out of the hole but it ran and if you gave it throttle it would keep running. Put the plug back in and nothing. Same thing. Here is a list of items ive verified since im kind of perplexed

-Verified the crankshaft PN was for a 58x system (new GM Crank)
-Replaced the cam sensor and cover with an LS3 setup (new)
-Replaced the crankshaft sensor (New GM black sensor)
-Pulled the timing cover, oil pump and oil pump gear to re-verify timing, it was fine and dot to dot
-Dropped fuel tank, cleaned the tank and put fresh 91 octane fuel in
-Verified fuel pressure going into the rail with a inline gauge
-Verified spark on all cylinders when cranking

There are no codes while cranking and even after the short run with the plug removed it only seemed to complain of the cylinder 1 issue.


Attached is the tune file as well as a few log files from it cranking and also from the starting situation when the one plug removed. Please keep in mind this tune wasn't meant to be perfect. just something to get it running and gather data. At this point the only thing mechanically I could think of would be the cam ground incorrectly but that would be pretty far out there and as previously mentioned, I have compression. I would normally degree wheel the cam on a performance engine but this was just a quick rebuild. Any ideas out there? Please take a look at the tune and log files and tell me if you see anything im not thinking of!

LC9 BASE START TUNE.hptLC9 No start 8Aug2019.hplLC9 Running no #1 plug.hpl

[blindsquirrel]

You installed a non-DOD cam and conventional lifters?

What does a compression test look like?

Can you get it to repeat that runs-with-no-#1-plug thing? A-B-A (runs; doesn't run; runs)? Just to confirm it wasn't a one-off?

[blades11b]

You installed a non-DOD cam and conventional lifters? Removed the whole DOD system. Replaced with LS7 lifters, non DOD 3 bolt cam and cloyes 4 reluctor wheel timing set

What does a compression test look like? From 148-152 PSI on all cylinders when cold cranking

Can you get it to repeat that runs-with-no-#1-plug thing? A-B-A (runs; doesn't run; runs)? Just to confirm it wasn't a one-off? If I remove the plug it will repeat every time. also does not matter what plug I remove, IE if i remove #4 it will start.

[blindsquirrel]

What if you leave the plug in but just disconnect the primary side of one coil? Or leave the coil connected and plug in the hole but put a spark tester in the wire?

1,4,6,7 were (are) the DOD cylinders, have you done the plug trick on 2,3,5,8?

[Camaro68]

Might want to check the crank sensor. The 58 tooth crank reluctors wheels use a gray sensor, the black sensor is for the 24 tooth reluctor wheel.

[ZincGT]

Vats?

[blades11b]

Might want to check the crank sensor. The 58 tooth crank reluctors wheels use a gray sensor, the black sensor is for the 24 tooth reluctor wheel.

So it is a black sensor but it is GM PN12585546 which is a 58x sensor. and was purchased from the dealership

[WAcord]

check coil packs wiring harness , sounds like its miss a ground

[Tre-Cool]

make sure you turn off the dod in the tune. ive seen cars not fire properly when the dod option is turned on in tune and the dod connector is unplugged.

[blades11b]

Update

-So got some more time to diagnose and it appears I looked over the spark quality when doing my initial diagnosis. I do indeed have spark but the spark is red/orange. When the RPM does pickup for a second (when it feels like its trying to start) which you can see in the log file the spark momentarily changes to a good quality of white/blue. then back to red/orange. The issue im having is that even with a subscription to AC Delco TDS there is no weak spark diagnosis troubleshooting information hell even the no start section is pretty poor. Here is what I verified in the mean time

-While cranking and back probing the pink wire on ignition coil harness the voltage does not drop below what the battery voltage is and stays at a pretty steady 11 Volts

-When checking the resistance on the black wire of the ignition coil harness from that wire to the battery ground I see a very acceptable amount of resistance, about .5 Ohms BUT when turning the key on that resistance jumps to approx 40 Ohms and while cranking it jumps to about 1k Ohms.

I have checked, rechecked and triple checked the grounds. They are all in their factory spots and tight. Any theories?

[blindsquirrel]

Measuring ohms on a wire that's carrying current will give you goofy results, measure voltage drop instead. Ohms is only reliable if the wire is inactive.

So terminal 'A' at the coil connectors go to a splice, and then to ground (all term 'A's from both banks end up spliced together and go to a single ground point). If there's high resistance between term 'A' and Gxxx (G102 for 2009, the latest I have access to) the voltage will be higher at term 'A' than at Gxxx, meter+ to 'A' and meter- to GND should show less than 0.5v while cranking. You can also check voltage drop between Gxxx (the actual ground point the coil harness uses) and BAT-.

Or, quick-n-dirty, jumper a good ground direct from BAT to one of the ground wires at the coil harness to see if you can make it run.

[Srblacks13]

Did your put the coil and coil brackets on the incorrect side? Try switching side to side

[BigDaddyG8]

So it is a black sensor but it is GM PN12585546 which is a 58x sensor. and was purchased from the dealership

i would still want the grey sensor......I think Camaro68 is on to something there..... what do I know I am a newb...LOL

[blades11b]

Did your put the coil and coil brackets on the incorrect side? Try switching side to side

To my knowledge the side does not matter with the coil packs

[blades11b]

i would still want the grey sensor......I think Camaro68 is on to something there..... what do I know I am a newb...LOL

Well its definitely a "grey" area. Pun intended. I did pull the sensor back out to verify the PN and it is indeed black but the PN is what it should be which is 12585546

[blades11b]

Measuring ohms on a wire that's carrying current will give you goofy results, measure voltage drop instead. Ohms is only reliable if the wire is inactive.

So terminal 'A' at the coil connectors go to a splice, and then to ground (all term 'A's from both banks end up spliced together and go to a single ground point). If there's high resistance between term 'A' and Gxxx (G102 for 2009, the latest I have access to) the voltage will be higher at term 'A' than at Gxxx, meter+ to 'A' and meter- to GND should show less than 0.5v while cranking. You can also check voltage drop between Gxxx (the actual ground point the coil harness uses) and BAT-.

Or, quick-n-dirty, jumper a good ground direct from BAT to one of the ground wires at the coil harness to see if you can make it run.

blindsquirrel I totally appreciate your help! but no dice. Voltage drop test from the power wire on the coils and volt meter directly to the battery Negative and there is no drop. reverse the drop test and go from the ground on the coil pack plug to the battery positive and same results. Both times no drops in voltage with Key on or when cranking in relation to what the battery voltage is. During this cranking the voltage isnt dropping any lower than approx 11-11.5v.

also even though this wasn't assumed to be the problem I still tested the resistance on the A terminals to ground on the battery and that entire circuit shows approx .4 ohms which should be acceptable for that length.

[Srblacks13]

I've seen many threads on LS1 tech about having the coil assemblies on the incorrect side and it running like shit. Try it out to rule it out.

[blindsquirrel]

blindsquirrel I totally appreciate your help! but no dice. Voltage drop test from the power wire on the coils and volt meter directly to the battery Negative and there is no drop. reverse the drop test and go from the ground on the coil pack plug to the battery positive and same results. Both times no drops in voltage with Key on or when cranking in relation to what the battery voltage is. During this cranking the voltage isnt dropping any lower than approx 11-11.5v.

also even though this wasn't assumed to be the problem I still tested the resistance on the A terminals to ground on the battery and that entire circuit shows approx .4 ohms which should be acceptable for that length.

No sir, you didn't do a voltage drop test, you were just straight out measuring voltage, and a voltage test doesn't show the small numbers you need to pin down a high resistance issue, if that's what this is.

Voltage drop is measuring the difference in voltage at two points along the same wire/circuit. The meter needs to display the difference between 'ground' at the coil pack connector pins and 'ground' at the BAT negative. This will be a very very small number if the circuit is in good shape, and larger as the circuit has progressively higher resistance.

Put your meter positive probe to one of the ground wires in the coil harness, and the meter negative probe straight to BAT negative. Both leads on only the ground side of the circuit, don't connect anything at all to the positive anywhere. You're only measuring the difference between 'true' ground and the 'ground' available to the coil primary circuit(s). Going from coil negative to battery negative will be checking the entire circuit through all the wires, splices and connectors in the entire ground circuit. To pinpoint where exactly the problem is, move your meter negative probe to another spot in the circuit, see if the same excessive voltage drop is present there as well. Basically split the whole circuit into halves - still problem, or no? If no, problem is in the other half that was eliminated. Check only that second half. Problem still? It's in this half somewhere, so split it in half again. Keep doing that and it will lead you straight to the splice, or wire, or connector where the problem is.

[Camaro68]

Thanks blindsquirrel, excellent explanation of the process for conducting a voltage drop test. The only thing to add is using an oscilloscope would give you an accurate way to measure the voltage drop as the circuit is placed under load.

[blades11b]

No sir, you didn't do a voltage drop test, you were just straight out measuring voltage, and a voltage test doesn't show the small numbers you need to pin down a high resistance issue, if that's what this is.

Voltage drop is measuring the difference in voltage at two points along the same wire/circuit. The meter needs to display the difference between 'ground' at the coil pack connector pins and 'ground' at the BAT negative. This will be a very very small number if the circuit is in good shape, and larger as the circuit has progressively higher resistance.

Put your meter positive probe to one of the ground wires in the coil harness, and the meter negative probe straight to BAT negative. Both leads on only the ground side of the circuit, don't connect anything at all to the positive anywhere. You're only measuring the difference between 'true' ground and the 'ground' available to the coil primary circuit(s). Going from coil negative to battery negative will be checking the entire circuit through all the wires, splices and connectors in the entire ground circuit. To pinpoint where exactly the problem is, move your meter negative probe to another spot in the circuit, see if the same excessive voltage drop is present there as well. Basically split the whole circuit into halves - still problem, or no? If no, problem is in the other half that was eliminated. Check only that second half. Problem still? It's in this half somewhere, so split it in half again. Keep doing that and it will lead you straight to the splice, or wire, or connector where the problem is.

blindsquirrel, yup total misunderstanding on my part. I did go back through it and do a proper voltage drop test on the ground circuit as well as the power circuit. results were rather inconclusive, the drop on the entire ground circuit was negligible (approx 2.2mv) only drop I found of a higher amount was on the ign circuit that feeds the coils. They had a 0v drop from the pcm to the coils but from the PCM to the battery they showed approx 26.5mv. Obviously the key had to be turned on to complete that circuit and check it.