I've got a 2004 Corvette that I just built a new motor for after cylinder 5 ringland let loose. It's an lc9 block, 799 heads, small summit cam, forged eagle stroker rotating assembly on a 3.800 bore, and the A&A kit I had on the old motor. Nothing wild in the scheme of things. I just got everything back together and now it won't start.

On vcm scanner I have rpm, MAF and MAP show changes, injectors are pulsing, timing advances, I'm reading fuel pressure at the rails, and the limited cam PID values change. Basically everything I know to check is showing it should be trying to start. However, it just cranks and cranks.

I'm not seeing any spark when I pulled a plug wire and tried the screw driver test or hold the plug wire near the plug or other grounding point. I have 12v to the pink wires on the coils and the grounds have continuity. I also went back and made sure I didn't have any grounds that I missed. So the common check the coil grounds and power has been checked. I'm at a loss as to what to check next.

Any help would be appreciated!

 

To maybe get some more traction here I'll go into more detail.

The build:

• LC9 block
• 799 heads with d-port exhaust
• Gm ls6 style valve springs
• Eagle forged 4" stroke crank
• Eagle forged I-beam rods
• McLoud RST twin disc with aluminum flywheel
• SUM-8719R1 cam
• New lifters and trays
• Hardened pushrods
• Upgraded trunnion rocker arm's
• Melling HV oil pump
• GM MLS headgaskets
• ARP head studs
• King XP bearings
• GM front timing cover with cam sensor
• Summit SFI balancer
• A&A supercharger kit with 3.8 pulley
• Stock intake and TB
• Summit forged pistons
• Mahle rings gapped to spec from factory sheet

Built the engine after #5 cylinder ringland let loose and took the motor out. I cleaned up the engine bay and rewrapped wiring, but didn't remove or change any of it. Cranks fine, but I have no spark.

Things I've checked or know:

• Crank sensor shows rpm when cranking
• Cam counts change
• Fuel pressure 58-60psi cranking
• Injectors pulsing
• Map and MAF both show activity cranking
• 12v and ground to coil packs is good
• Can't find any missing engine grounds
• Multipack grounds on frame rails near radiator are tmod upgrades
• Grounds under batter and under brake booster are clean
• New battery on charger/tender when cranking (voltage doesn't drop to concerning levels)
• No spark confirmed with inline tester
• oscilloscope shows no activity on evu trigger wire

In my understanding by all accounts it should be firing right up, but it seems like the p59 PCM is not cycling the ignition trigger wires to actually give spark.

 

Bad PCM??

Rick

 

It's on my list of possibilities as I run down options. I'm hoping to get the PCM exposed today after work to look for any damage. I'm scratching my head trying figure it out though. Feeling a little defeated at the moment lol

 

Back ttt

 

Honestly sounds like you’ve got most of the normal stuff covered already. One thing I’d definitely verify though is the 24x/58x stuff since you’re using an LC9 block with a P59 PCM. Did you swap the crank reluctor to 24x or is the LC9 still running the factory 58x wheel? Also what crank sensor are you using? Same with the cam setup, are you running a front cam sensor conversion and if so what cam gear/sensor combo did you use? Black or gray sensor? Any adapter harness? I’ve seen mismatched crank/cam setups cause exactly this where you get RPM, injector pulse, fuel pressure, etc but the PCM never actually triggers the coils.

 

I appreciate the feedback and help! I did make sure that I have both a 24x crank (assuming Eagle put the right reluctor on the crank) and a single pole cam gear on the front. If I understood the info on the forums and such should be the correct setup for my needs. The crank sensor was yanked from the ls1 and the cam sensor (tan oddly enough) is the one that came with the timing cover set (PN 12633906). I do have cam count changes on HPtuners with it and verified that I did not need to swap pins A and C with not using the oem extension on the cover to get a readable signal. However, I don't know what normal counts on cranking should be to ID if there's an issue there. On paper everything should be copesetic, but I'm human and can make mistakes... Like not choosing cheaper hobbies lol.

For the cam sensor what I could find is that the gen 3 and 4 are interchangeable on OEM setups, but I also found that the Holley EFI systems are sensitive to them. So, def some conflicting info in my research. However, I tried cranking even without cam sensor plugged in and per the FSM it should still start without it though will have longer crank time due to lack of sync.

 

At this point I’d probably start by verifying the crank reluctor is actually 24x and not just assuming it since everything else sounds pretty solid on paper. I’d also inspect the crank sensor and wiring near the starter really closely for damage or spacing issues since you’re getting RPM but still no coil trigger output from the PCM. While cranking, look in VCM scanner and see if it’s actually achieving crank sync and not just showing RPM. After that I’d ohm out the ignition trigger wires from the PCM to the coils and inspect the PCM connector pins for anything backed out or bent since you mentioned rewrapping the harness. If all that checks good, honestly I’d try another known good P59 PCM because with injector pulse, fuel pressure, RPM signal, and zero ignition trigger activity, it really sounds like the PCM is deciding not to fire the coils or the ignition drivers inside it are dead. I have an lc9 in my truck with a 24x reluctor and I had similar issues with my truck but im on holley and I ended up switching my cam and crank sensors and then finally I got on the phone with holley and they had me switch some wires around at the ecu and it crunk, im not to familiar with hp tuners but maybe you can give them a call?

 

Thanks again for the info! On a high note, I was able to see my reluctor wheel from some of the pics I took putting it together and it's most definitely a 24x style one, one problem down. I'll still put inspecting the CKP sensor pigtail and mounting hole for any abnormalities as I work through possibilities though.

When I rewrapped wiring I didn't alter anything really, just the sections in the engine bay where tape was falling apart or the loom wrap was falling apart I retaped. I cleaned dirt and oil off of connectors as I went along too with brake clean (I know not as nice on connectors as CRC electronics cleaner), but nothing looked frayed or damaged. But that doesn't mean I didn't accidently tug too hard on something or simply miss damage.

As far as anything needing re-pinned the only thing of note I found was for some people using the stock extension on the timing cover sensor sometimes swaps pin A and C and won't read that way. I'm reading cam activity on HPtuners, so that doesn't appear to be the issue. However, I've not found a particular PID listed online or rummaging through HPtuners that says there's a way to easily identify sync. All I'm finding is to look for CKP rpm, cam hi/lo and cam low/hi counters, and cam offset (I think that's the name) PID's. Which it should start as long as the CKP sensor is registering correctly and the coil harness circuit is intact. A couple tuners have been quick to firmly reiterate if I'm seeing RPM the crank sensor isn't the issue, if that matters any at this juncture.

As much as I hate the parts cannon I went ahead and ordered another p59 ecu and if I'm lucky it will be here Friday or Saturday at the latest. It's not much more than a crank sensor and a lot less labor in the driveway. Barring lightbulb moments I think it's down to it or some intermittent wiring gremlin. I have a post on the HPtuners forum seeking advice there too, but not much traction there yet. I'm waiting on someone to comment on the cranking log to see if they spotted anything weird with crank signal or some other thing I'm just not educated enough on to know is the culprit.

 

Doing some digging it looks like the Delco CIC IC that's integrated into the PCM board plays a bigger role than just cycling the coils based on CKP rpm. There's safeties and checks coded in on it too, but that's way deep in the woods and pcmhacking has very limited info on it outside of a Delco document that discusses it's functions. So, if all else checks out a bad PCM, or at least IC driver in it could be bad or not happy with what it's seeing. Way out in the weeds, but if everything else has checked out on the external wiring side the PCM moves up on the list. And even then I'm not above admitting my rudimentary understanding of it's interface and function could be completely wrong.

 

Honestly I think you’re getting close. Confirming it’s actually a 24x reluctor rules out the biggest red flag. I agree that if it’s seeing RPM then the crank sensor is at least doing something, but the weird part is still having injector pulse, fuel pressure, RPM, cam activity, etc with absolutely no coil trigger activity. That’s what keeps making me think either something on the ignition trigger wiring side got damaged or the PCM itself just isn’t commanding spark. Honestly I don’t think you’re crazy for trying another PCM at this point, especially since it’s easier than tearing back into the engine chasing something that may not even be there. I’d still inspect the crank sensor wiring closely while waiting on the PCM though. Crazy part is Im sure i have a p59 in my shed somewhere, I initially had a p01 then switch to p59, then to holley. Pretty sure I have then both somewhere in a box in my shed.

 

I'll being doing a test light load test on the 12v and ground circuit when I get home at the request from one of the folks on HPTuners forum. But if it confirms a good circuit I believe it further supports issues at the PCM or with the lo ref circuit. Since it would be unicorn level rare for all 8 coils triggers to fail at the same time, so it must be something on the shared lines. Which I suppose is why everyone directs me to grounds and 12v checking since it's cranking and everything else seems copasetic. Not like I can swap out the computer yet anyways, it still has a couple days travel time left. Might as well keep running down possibilities until it shows up or the car runs.

 

Yeh I agree with your thinking there. It would be insanely rare for all 8 coil trigger circuits to randomly fail at once, which is why this really feels like either a shared power/ground/reference issue or the PCM just not commanding spark. Doing a loaded test on the power and grounds is definitely worth doing because continuity checks can lie sometimes. If all that checks good though, the PCM moves way higher on the suspect list in my opinion. At least you’re narrowing it down logically instead of just throwing random parts at it.

 

Whelp, I'll know more when I get home, but I might have found the issue. I was running through things I'd touched or replaced and with everything coming back to the coil circuit I went back and looked at the cheap replacement sub-harness I got compared to the OEM one. The big 7-pin connector is correct, but the coil pigtails are mirrored.

Short of the long, instead of A-D being ground-lo ref-trigger-12v it's 12v-trigger-lo ref-ground. Had I replaced them after it was running I would have caught it right away like reviews I read, but instead I did it along with the new engine build and it was lost in a sea of 800 other possibilities.

 

ah that will definitely do it, if thats the case you should hear it run tonight. Let me know how it goes, in the meantime ill be adding traction control to mine tonight. I have it all wired up, I just need to set it up in holley.

 

Okay, shocker, re-pinning the coil pigtails fixed the issue. Coil 3 is showing misfire and HPTuners PID is showing fail for that coil now, but is likely the trash sub harness. I have a better quality one on order from Summit and am kicking myself for not saving the old OEM one that though ragged, worked without issue. Normally I hoard functional parts like most people who wrench more than oil changes, but must have got tossed in an Amazon box purge. A plus of living where I do in GA normal shipping from Summit ends up being free next day shipping for a better quality sub-harness.

There's still issues with a hunting idle and bizarre bank 2 hunting STFT that starts in single digits and then rises to like 50+ then resets and starts over, but it at least cranks up every time. Bank 1 is showing STFT around 2-3%+, which I can't complain about with a fresh build with different cam and bigger displacement. Looks like that o2 sensor is flat, so I'll check that wiring next. Though I new sensor isn't that expensive if it crapped out.

Also, best of luck with the traction control, may it go off without a hitch for you. What are you building, btw?

 

That misfire on cylinder 3 honestly still sounds harness related too, especially with it being a cheap aftermarket sub harness. The weird STFT behavior on bank 2 could definitely be related to the O2 sensor or wiring if it’s flatlining, especially since bank 1 sounds pretty normal for a fresh setup with a cam and stroker combo. Sounds like you knocked out the major issue and now you’re down to the normal fresh build gremlins lol.
Mine’s a 2000 Silverado single cab short bed with a turbo LC9 and Holley Terminator X Max. It’s already built, I’m just always adding stuff to it. Right now I’m adding traction control since I finally got the wheel speed sensor wired up

 

Nice! I bet that's a fun truck, how big of a turbo? I told myself the A&A kit on the stock motor would be fine and then when it blew I was like well... for longevity forged would be good. Then was like well stroker crank and rods in 24x is cheaper than stock in 24x. So, might as well get that, probably should get a cam since the low end on the stock 5.7 seemed a little flat until the SC kicked in... And then 4500 later here I am. I should got into yoga or gardening lol

 

I went through the same thing, I had a stock lm7 in the truck before this and I pushed it to around 18 psi which had it a little over 750 wheel and it was OK on the street but the first track session it spun a bearing. Im sure a cam would definitely help.
my truck specs:
-lc9 5.3 with eagle rods and 20 over summit pistons
- cam 227/234 .600"/.600" 114 LSA 111 ICL- cleetus McFarland bald eagle boost cam, stock crank, with 24x billet reluctor
-vs racing next gen 2.5 78/75 turbo, 60mm wastegate, 50mm wastegate, dual mac valves, viar air tank.
-bosch 210 injectors
-huron speed fuel hanger with dual 525 pumps
-flex fuel sensor(i always use e85)
-treadstone 4" intercooler, all my piping is custom made, my buddy has a shop
-holley ecu with current performance integrated harness, po1 ecu controls factory components, ac, radio, lights, dash, etc
-exhaust is kind of interesting, i have a 4" v band that comes on the turbo and we have it splitting. One directions goes to a 4" fender exit with cutout and the other is 3" and goes under the truck to full exhaust that runs out the back of the truck to a magnaflow muffler. Normal driving conditions it goes out the back unless i flip a switch or go wot in which it goes out the fender.
​​​​-circle d 258mm 3800 converter
-2/4 drop truck is c notched with caltracs, right now it just has a summit brand shocks but plan to do the atomic fabrication kit front and back with viking shocks in the real and coilovers in the front in which ill be going 4/6
- franks level 4 4l60e with rossler transbrake
- single plane manifold with edelbrock 90 with fitech 90mm throttle body.
- Im sure im forgetting something but I think thats the bulk of it. Oh racestar 17" wheels with mickey Thompson et street r in the rear(305/45) and regulator street tires in the front 215/65

 

4l60E's have really come a long way with rebuilds that can handle power. I feel like even just 10 years ago that kinda juice would've had to of had a 4l80 behind it, or a cost prohibitive boutique 4l60. That's a really cool setup for the dump pipe on the turbo, nice manners on the street and a screamer with a flip of a switch. Sounds like you modified the old school electric dumps concept to your turbo setup, pretty cool. Custom stuff like that I find really interesting, because it's unique and thinking outside the box. Not that there's anything wrong with off the shelf stuff, but those aren't things that generate conversations in the pit or at car shows. The most exotic things on my c5 are I mashed together some trashed 3lt c6 seats I got of FB for 150 with some 1lt 2013 c6 seats and did a re-dye on them in Ford King Ranch along with the door panels, glove box, and knee bolster. The oak tan was okay, but it's a dime dozen factory color and the 2013 seats needed re-died anyways.

I'd contemplated looking at doing something hybrid with the terminator x and stock p59 to maintain factory functions, but didn't research it for fear that I'd decide I needed to do it. The limitations of the p59 with having to trick it for bigger injectors, the low resolution maps on 2 bar, and other misc stuff is kind of a bummer to work around. So, I've mixed feelings on seeing you're running both successfully lol.