Crank No Spark LS Swap

[MrBearclaw]

Hey Guys,

I've got a 79 Camaro that I've been working on swapping over my free weekends for the past year. I've got everything in the car, wired, tested and I can't get the thing to fire up. I've checked all my wiring, fuses and grounds at every point I can think of with the key in both the "run" and "start" positions. I even got a new crank position sensor, and my logging software shows that the engine is cranking at roughly 165 RPM when attempting to start.

My problem seems to be spark, the ECU will just not send a spark signal to the coils. My hot and ground wires to coils and injectors tested good all around. I've verified that VATS is disabled in TunerPro multiple times now, and I've re-flashed and retested with two different PCMs. Anyone have any good insight on what I could be missing? Any help would be greatly appreciated.

[B52Bombardier1]

How do you know it is not sparking? Noid lights? Timing light? Any codes? Just for grins, and I don't like to recommend this stuff but . . . squirt a shot or two of starting fluid into and past an open throttle body. If you have spark, the starting fluid ether will find it. Just don't use it as a crutch to get your engine to start because the fluid is tough on the cylinder oil film.

What engine model and year?

What PCM type?

Rick

[MrBearclaw]

Hey Rick,

I've pulled the plugs to check for spark, and we also used a noid light on the coil connectors. There were a couple of codes when using the PCM original to the motor (a LM7 out of a 2005 Tahoe, DBW), p0220 and p2135. When I flashed the tune to another PCM out of a 2003 L59 DBW Suburban and tried it, the codes went away. Not sure why, and I'm not really sure how to tell what kind of PCMs they are.

I tried starting fluid the other day and got nothing. I haven't changed anything in the tune other than a segment swap for a 4L80e and VATS. Rails have flex injectors in them now, haven't figured out the right data for updating this in the tune yet but I don't think that would keep the thing from starting, right?

[B52Bombardier1]

Hello,

What do the colors on the PCM connector locations indicate? Red and blue? Or blue and green?

What is the operating system number you are using? Are you using Tuner Pro RT to edit your tune?

What program are you using to write your tune to the PCM?

Do you have full time power to pin 16 on the OBD2 connector?

What vehicle is the source of your wiring harness? Who made it or re-pinned it and how were they guided on what wires to change? My guess prediction is that your PCM does not have power during cranking or maybe does not have all of its required ground ports properly grounded.

Rick

[MrBearclaw]

Both PCMs have blue and green connectors. I pulled the harness out of the same 2003 Suburban that I got the second PCM and the flex injectors out of. I re-pinned the harness using LT1swap's guide, the only things I changed were a couple of pins for electric fan controls and I added a couple of pins for the 4L80e. I haven't thinned out any unnecessary wires yet.

The OS I've got flashed to the PCMs is 12587603, I used TunerPro RT to delete VATS, LS Droid for the segment swap, and PCM Hammer for reading and writing.

The OBD2 connector has power all the time, and I checked all of the PCM ground, ignition and battery supply pins. Everything seems to have power in run and start.

[MrBearclaw]

Here's a copy of the .bin I currently have in the PCMs if its helpful.

04Chevy1500LM74X2OS125876034L80SegSwapVatsDelete.bin

[MrBearclaw]

Finally, I got the problem figured out a couple of weeks ago. Of course, the hacked up junkyard harness I'm using had a ground terminal ripped off in a hidden arm of the harness. Made me feel pretty dumb but I'll never do it again, that's for sure! Also, the TPS sensor was faulty so the engine would start but would only run for a couple of seconds before shutting off. I thought this was VATS at first and re-flashed the PCM a couple of times before I realized it wasn't changing anything.

Now I'm fairly sure I roasted the pedal position sensor when I cut out a big chunk of the truck pedal I'm using and welded it back together to make it fit under the dash. It's always something.