LS1 Won't Start
 

*SOLVED!* The ignition coil harness was correct left and right, but incorrect front and back. Cylinder 1 was swapped with Cyl 7, 2 with 8, etc. Corrected the coil harness and she runs now.

Hi All! I have a 2002 LS1 from a Trans AM that won't start and I've gotten to a point where I am out of ideas on where to go next. I could REALLY use some help from the experts here! It's a swap into a '79 Camaro with a standalone harness.
* Edit: update below, replaced the PCM, getting crank signal, still doesn't start.*

Symptoms

• It has at least intermittent spark and fuel. It is acting like the ignition timing is way off and compression/spark is fighting against the starter, popping out of the exhaust and intake. Sometimes there is no popping and the engine is just turning over. After 20 seconds of cranking there was fuel burning in at least the drivers side open header. There is no exhaust on the car but O2 sensors are plugged into the headers.
  
• I've measured 10 volts at the computer ignition relay during cranking. >12.5 volts when not cranking (key on).
  
• fuel pressure is set to 58 lbs from a remote regulator and gauge. fuel pressure is bleeding down with key off to 20 lbs on its own in a couple minutes indicating a problem, but I dont think this is keeping me from starting if pressure is good while cranking. OEM regulator is still installed and I have not yet measured pressure directly at the rail after the OEM regulator, but would this cause it to act like timing is way off?
  
• No PCM codes after cranking 30 seconds on >three attempts.
  

What I've tried:

• Attached 40 amp boost pack while cranking to make sure its not a low voltage issue. engine turns faster but no change to the presumed timing issue and no start
  
• Replaced Crank position sensor. It seemed like a good place to start. The new ACDelco sensor threw a CKP code P0036 and fit poorly. I replaced it again with a second new sensor. No change to symptoms in any of the cases and currently the third (new) sensor is installed with no check engine codes.
  
• Verified CKP and CPP pinouts with diagrams I found here. Connector positions go to the correct pins in the red and blue pcm harness.
  
• Tried starting with cam position sensor unplugged but crank position sensor plugged in, in case the cam sensor is the issue, even though there is no code. No change.
  
• Looked inside the crank position sensor hole. The reluctor wheel is there but other than that not very helpful.
  
• A BIG ONE - after tracing red and blue PCM connectors, I discovered that JEGS connected their white wire, pin 10 TACH signal, to a cluster of other white wires from their fuse block (12 volts ignition hot). I assume this is an error, and Pin 10 tach signal should not be fed 12 volts. I found it because it was back feeding voltage to my gauge cluster with the key off. I rewired Pin 10 to run to my tach signal input for my gauge cluster. I do not know if I have RPM signal because I can't get it started.
  
• It ran before I tore the whole car down for rewiring and rebuilding. What did I do or miss?
  
• I thought maybe the injector or coil plugs are swapped from side to side. I installed it based on their picture on their product page, but thats the only documentation they offer. Jegs wrapped the wires so I don't think the individual injector pigtails and the main plugs are long enough to swap the drivers and passenger side, but their picture might be wrong. But given the Jegs error above, maybe there is an internal error I can't see also. I can't find a wiring diagram showing individual injector wires or coil wires to validate, by jegs or otherwise. Jegs used their own wire colors so thats not helpful either.
  
• I've plugged in all the sensors from the standalone harness. All are there except oil pressure switch and oil level sensor. There is a MAP and MAF plug. One strange question, there seems to be 2 MAP sensors, one on the intake tube after the MAF but before the throttle body. One on the back on the intake near the firewall.
  

Relevant background information:

• The car was a half finished project that I inherited. The previous owner was the Emperor of the whole kingdom of idiots, but I'm fairly confident I've fixed everything he did.
  
• He upgraded the intake, heads and installed a street cam. I was told the bottom end was oem/stock. I removed the heads to inspect. some light glazing on the cylinder walls, oem pistons, stock bore, seemed to indicate stock bottom end. I did not remove the rotating assembly though. Reinstalled with GM gaskets, ARP head bolts, followed torque specs.
  
• I reinstalled the heads, followed the cylinder procedure to torque down the rockers.
  
• They replaced the cam, timing set, and oil pump along with heads and intake it seems. I did not remove or reinstall the cam, but I did get the part number. I checked cam timing while it was apart by putting my finger is spark plug #1, feeling for peak pressure. it coincided with the timing set dots lining up at 6 and 12 so seemed to be correct by the previous owner and I didn't change anything here.
  
• appears to be an OEM computer, not known. He says all parts were from a 2002 Trans Am so I assume this is the computer, along with the engine.
  
• He bought the standalone wiring harness from JEGS. Part Number: 555-10414. This is relevant because their documentation is extremely poor, he removed the wiring tags, and I've already found at least one big mistake on JEGS part.
  
• It started but ran poorly after it warmed up when I looked at the car the first time, before all of my work. He had huge wiring problems everywhere which I assumed was probably the issue. He said "It needs a tune". After my reassembly and reinstall it doesn't even start. Is it something I did?
  

I'm trying not to panic but I need help! my worries:

• Since the bottom end is stock and hasn't been removed I'm really hoping and thinking it is not a reluctor issue, and I don't have a code.
  
• I am paranoid the cam timing is off, but is it even possible to be off 180 degrees since its computer controlled? Cylinder 1 is the front drivers side correct? and the timing set dots should line up here when at the top of its stroke? I could see how I might have been off a tooth or two, but that shouldn't cause backfiring out of the intake or exhaust I wouldn't think. Also it ran previously, and I didn't change the cam timing, so I was assuming this wasn't it.
  
• Could a different sensor trick the computer on ignition timing somehow? Or are any of the other sensors used during cranking? I did clean the MAF (Gently I thought), but I know they're delicate. Could a bad MAF cause a no-start without a code?
  
• Did Jegs fry my computer by feeding 12 volts to pin 10? Or is there supposed to be 12 volts supplied here? Seems like a huge quality control problem on their part.
  
• Is my computer bad?
  
• WHAT DID i MISS?
  

Thank you everyone for your help. Please let me know if there is any information or pics you need and i'll get started.

Wow, you documented a lot to think about. (Tha't better than those to under-document things.)
Can't be sure, but this is sounding like a wiring, sensor or PCM problem.
First, your sometimes "compression/spark is fighting against the starter" sounds like a missing signal from the cam sensor. With a running engine, disconnecting the cam sensor gives that symptom 50% of the time and the other 50% it starts and runs fine.
Next, there have been several posts here about counterfeit ACDelco sensors sold on Amazon and Ebay. On Amazon always check who the seller is - if Amazon itself, it likely is genuine, but if e.g. CheapoCarParts, its likely counterfeit and flakey. Summit or Jegs should be genuine.
Feeding 12V into the tach output of the PCM might have damaged it in unknown ways.
Does a scanner connect to the PCM? If not the PCM is toast.
Assuming the scanner does connect, it should show the RPM when cranking, likely in the 150 RPM range. If no RPM, then bad crank sensor or wiring to it.
Too bad that JEGS harness has the error and no doco; its also expensive at $400. Maybe I've been lucky but I have bought LS swap harnesses on ebay for $200 and they were of excellent quality.
No, a bad MAF will not prevent a start.
Assuming the engine previously started/ran with the same camshaft timing, you only need fuel rail pressure, working injectors, sa crank sensor, working PCM and correct coil wiring for the car to start. Not sure if a MAP sensor is even need to start, but definitely to run. Even if the injector wiring is wrong, it will start, just not run well.
If you have an old-style timing light, you could figure out if the coil wiring is reversed right to left. You would have to mark TDC on the balancer, trigger the timing light from the cylinder 1 spark plug wire and watch while someone cranks the engine. The timing light should fire somewhere around 10 degrees BTDC. It is like 100 degrees BTDC, you are trigging off the signal for cylinder 2.

Perhaps someone else has a more definitive and simpler diagnosis and/or something I missed.

Hi Mrvedit, Thanks for the reply!

I agree about the cam sensor. I cycled the key on and off ~20 times at this point, trying to start it each time. I decided it should have started at least once based on 50/50 odds, but who knows maybe I got unlucky! I dont mind pulling the intake off and replacing the cam sensor if we get to that point. I'm also worried the aftermarket cam has an internal problem with its reluctor wheel somehow, but i guess thats unlikely. Cam is: BTR CAMSHAFT – LS1/LS2 – N/A STAGE 2 – 32738132R0 for reference.

The ACdelco sensor was purchased from Advance Auto Parts. Either way, i've returned it since it was throwing a faulty code.
My OBD2 code reader connects. Unfortunately I don't have a scanner but I'm feeling like I might need to buy one. Anyone have a favorite recommendation? I might need to do a tune because of the cam so it would be nice if I purchased something that could do both. I've used HPTuners in the past to deactivate DoD on my 6.2L LS (different car), but I'm a novice overall.

Great idea about marking the balancer. I do have a timing light. I will check that in the next day or two between work. In theory, without a scanner, i should also be able to see if its consistently firing with the timing light, or missing some of the crank position sensor pulses. I can check and see if it's firing all cylinders while cranking as well.

The HP Tuners Scanner will show RPM even when cranking. Should be able to even log it for checking later.
Sounds like you have a genuine crank sensor then. A 24X for an LS1, right? I think the next step is to confirm the scanner reads cranking RPM.

Update:
Tested spark with an inline spark tester. I am getting consistent spark on both banks while cranking. I don't know timing yet but see below. I can also hear the injectors clicking clearly while cranking. I have a fuel rail pressure tester on order.

I have PCM Hardware No. 16220610. It seems the previous owner was not honest with me that it is out of a 2002 trans am, because this number seems to be a earlier silverado or a few other vehicles, and for a 5.3L? Will this work with my engine without a reflash? I'm really confused how this ran before I bought it now, but it definitely isn't what I thought it was and seems someone was in it previously, because two of the case screws were missing. I connected my cheap bluetooth OBDII scanner and it will not connect. It will read trouble codes, but won't show me vehicle information, live data, or sensor inputs. I tested the same reader on another car and it worked perfectly. My handheld scanner reads trouble codes, but I guess the PCM only has limited functionality. It seems I have a bad PCM?

Question: What replacement PCM would work best for a 2002 LS1 with an LS6 intake, #243 heads, and the above mild street cam, 4l60e, swapped into a 79 camaro? I suppose I should have a 24x reluctor, but now I dont know for certain. Any recommendations, and for software choice as well? Perhaps a good supporting vendor? Thanks again.

From what I just researched, the 16220610 PCM is from a 1999-2002 Chevrolet Silverado. What's important is that is has the Red and Blue connectors and is NOT from a 97/98.
A "411" PCM will work for you, is 24X and is very popular.
I'm sure someone will confirm or correct me, but the 16220610 might be the same hardware as a 411, just with a different OS, which is easily updated with HP Tuners.
Here is a HP Tuners thread on it: https://forum.hptuners.com/showthrea...truck-411-pcms

Good news is it does have the red and blue connectors as labeled on the case. What worries me more is that my scanner won't fully connect to it, so I'm assuming it's a bad PCM at this point and going to order a replacement. I'm guessing feeding 12 volts to the tach output probably wasn't good for it. I'll post back when it arrives.

Yes, it seems likely your PCM is bad. Reason I mentioned that the 610 might be the same hardware as a 411, is that the 610 is often listed cheaper on ebay than the 411. But wait for someone to confirm that, or just buy a 411.
Most ebay PCM vendors will write any VIN into it, disable VATS and optionally disable the rear O2 sensors.
If you need a tune for mods, I suspect some of the pro-tuners on this site can sell you a 411 with a good tune for those changes. @minytrker might be one.

Hi All, I received my new tuned PCM today from LSX power tuning. The good news is my cheap scan tool does connect to this one and I can see *sortof* live data. I can see ~100 RPM while cranking, o2 sensor voltage, etc. The bad news is that the symptoms are the same, the timing or something is definitely off and it won't start. Maybe I'll buy a HPtuners so I can see better resolution and trends, but I'm tired of throwing money at a car that can't run. I'm completely out of ideas at this point and could use some help. Thanks.

Well, you are actually making progress, By reading 100 RPM cranking we now know your crank sensor is good. And you say you have spark.
Lets assume the reluctor wheel is correctly positioned and your camshaft is timed correctly. We now need fuel.
Have you tried spraying starter fluid into the TB while its cranking?
You might roll up some masking tape for 1/16" thickness and stick it in the TB to open the blade a bit.
Have you tested the fuel pressure at the rail?
Are you running with or without MAF?

Have you rung the harness out against the engine powertrain schematics, not just a couple wires? I wouldn’t trust any store-bought harness.

Got my fuel pressure test kit. The gauge on the regulator was off (or the test kit is off?) and I had low pressure. I've adjusted fuel pressure now to read 58 PSIG on the test gauge, and 61 PSIG on the regulator gauge. Progress at least.
Running with a MAF. Although I should probably verify with the PCM programmer that that's how they set up the new PCM.

I've decided to order a new cam position sensor. Interestingly the engine sounds exactly the same and nothing changes with the Cam position sensor unplugged or plugged in. I have verified the wires and pins are correct but my scanner is too basic to see if I am getting a signal.

I can hear the injectors firing while cranking and verified consistent spark while cranking on cylinders 1,3,2 and 4. Just checked the front two on each side but don't see why the back would be different.

@Tommy, I agree not to trust the harness and already found one serious issue with it. I have checked pinouts on CKP, CPS, all grounds, ignition hot, and 12V constant power. I haven't checked every wire however. Which others do you all think could keep it from starting? Happy to check those. Thanks again.

I've got updates! It runs! The harness was correct left and right side, but incorrect front and back for the ignition coils. 1 was swapped with 7, 2 with 8, etc. I blame poor documentation from JEgs, but at the end of the day its my fault. Since the wire colors are wrong I had to trace each wire to the PCM.

I have two check engine lights, one for a bad MAF and for a MIL circuit malfunction, but I should be able to solve those easy enough.

Disappointingly, the custom PCM I just got won't start without full throttle, won't idle below 2000 RPM and backfires badly. The stock PCM I thought was bad (and might be) runs the car great without issue. So now I have two bad PCM's, but thats a customer service issue I'll work with LSX power tuning on.

Thank you for all of your help and getting all the other issues fixed as well. I'm considering this SOLVED!

Great news for you and thanks for the update. We will remember to have future people check the coil wiring when the engine doesn't start after a new harness.

If all had worked first time, you would not have learned much; now you have learned a lot. I bet you feel much more comfortable with your car knowing you could probably solve anything.