2008 L76 6.0_E38 No spark_standalone

[GAMEOVER]

I transplanted a 2008 L76 6.0(E38) into a 1985 Chevy Blazer last April, everything was working good, customer has put about 5500 miles on engine since swap...
This morning engine wouldn't start, so I go over and try to diagnose
Battery has 12 volts
Engine turns over easily
Fuel pressure is at 58psi with key/ignition ON...With key on fuel pump primes for 2-3 seconds
There is power at Coils & Injectors...
12 volt power at pins 19, 20, & 47
NO DTC's
All grounds are hooked up...
I checked all connections and everything is fine, could it be a bad Crank or Cam sensor? Engine was bought at junkyard with about 10,000 miles on it
If it was a bad crank or cam sensor wouldn't it throw a DTC?

[ChipsByAl]

So during cranking you have injector pulse? Make sure you have 12 volts during cranking too.
Al

[GAMEOVER]

I do have 12 volts during cranking...Didn't check injector pulse!

[joecar]

The CKP signal triggers both injector firing and ignition coil firing...

if you get one and not the other, then persue this (e.g. problem is in either injector circuit or ignition circuit);

if you get neither then check fuses (typically there are two fuses, one for each bank, each fuse feeds injectors and coil on that bank);

if fuses ok, then check for rpm signal (use scantool to see if RPM shows reasonable value during cranking).

Also check for CMP signal, sometimes this can prevent a start, but the ECM has logic to determine the correct phase from CKP and misfire counts (and from spundown crank position when engine was last shutoff).

[gmh308]

I do have 12 volts during cranking...Didn't check injector pulse!

12 volts during cranking? At the ECM? That's pretty unusual. Pretty amazing battery if it holds 12v during cranking. More normal to see 10v.

[GAMEOVER]

Actually, it is a pretty amazing battery...
But your right, it was 11.2 volts during cranking....And thanks for your HELP!!!

[gmh308]

Actually, it is a pretty amazing battery...
But your right, it was 11.2 volts during cranking....And thanks for your HELP!!!

Yes that is a good battery! Have seen LS's turn over fine but not start and it has turned out to be that on cranking the batt voltage drops too low and the ECM turns off. New batt and AOK>

[GAMEOVER]

Checked for 5 volts at CKP & CMP sensor plug and 5 volts are present...
Checked for ground at CKP & CMP sensor plug and ground is good...

Before all this started, owner told me he installed 2 new shocks but mounting tabs weren't the same, so he welded new tabs in place, but he didn't disconnect the battery... The following day is when the motor wouldn't fire.
This evening I tried a ECM from a running L76 6.0 and engine didn't fire...

[gmh308]

Checked for 5 volts at CKP & CMP sensor plug and 5 volts are present...
Checked for ground at CKP & CMP sensor plug and ground is good...

Before all this started, owner told me he installed 2 new shocks but mounting tabs weren't the same, so he welded new tabs in place, but he didn't disconnect the battery... The following day is when the motor wouldn't fire.
This evening I tried a ECM from a running L76 6.0 and engine didn't fire...

Like Joecar indicated, did you check crank and cam rpm on the scanner? And also look at injector & coil status?

[GAMEOVER]

Cranking RPM shows 112 RPM, then goes up to 200-300 RPM...
Will check CAM rpm and injector & coil status today...

[turbo_bu]

The CKP signal triggers both injector firing and ignition coil firing...

if you get one and not the other, then persue this (e.g. problem is in either injector circuit or ignition circuit);

if you get neither then check fuses (typically there are two fuses, one for each bank, each fuse feeds injectors and coil on that bank);

if fuses ok, then check for rpm signal (use scantool to see if RPM shows reasonable value during cranking).

Also check for CMP signal, sometimes this can prevent a start, but the ECM has logic to determine the correct phase from CKP and misfire counts (and from spundown crank position when engine was last shutoff).

Is this only on the E38, or can the ol' LS1 PCM's also run off of only the crank sensor? Just curious for troubleshooting in the future.

[joecar]

Yes, according to the GM Service Manual.

[GAMEOVER]

Well, I went and bought a new crankshaft position sensor and It FIRED right up.....:D:D:D

[joecar]

Take a log of starting up with the new sensor, what rpm does it show during cranking...?

[GAMEOVER]

Will do that this evening Joe...