LS motor with no spark?

Helping my step father work on his El Camino tomorrow.  Not sure what is going on but it seems to have lost spark.  He says that he has checked the wiring and doesn't see anything amiss, but beyond that he is more a carburetor, cap and rotor guy than a coil on plug and EFI guy.

Im a little fuzzy on the details of the swap and all, but I know the motor was pulled from a truck and it ran well enough for a couple years, but he let it sit for a couple years while personal issues popped up and it hasn't run since.

I'll get more details on the motor and what he has checked and whatnot, but I figured I'd drop a line and see anyone had some simple stuff to look at and check off before I get there tomorrow 

See if you can find instructions for testing the cam position sensor and crank position sensor with a multimeter 

when i did the Datsun 5.3 it came out of the van running and wouldn't spark in the car and I found tests online and my cam position sensor was bad

May have to write out vats. Even though most trucks don't have it, somehow the ecm revert back to saying you need it.

So the donor was a 2000 GM 1500 work truck, 5.3L.  Worked one day and didn't start the next.  Based on what I've read I think I agree with the VATS system being suspect?  Have to dig into the system and see if we can figure out where the people that did the swap put everything. 

So, finally back at ma's house to help with this.  Last time we didn't have a good battery and the store was closed for Memorial Day. 

No fuel pressure, no spark, I cant track where the plug to the key is, so I'm not sure how to track down where those wires are to see what the shop that did the swap actually did.

Does anyone know where the VATS system plugs into on the other end?  One side is at the ignition tumbler, where is the other? The ECM? Anyone able to supply a pinout?

Go to lt1swap.com they have ecm pinouts of all the ls stuff

The fuel pump should prime with a VATS mismatch.

Did they wire a check engine light in?  I hate that I have to even ask this.  But assuming they did, make sure the light comes on key on/engine off.

Not that I saw.  There is an OBDII port that connects

If the fuel pump isn't priming I would suspect either switched 12V or Ground problems. I'm not an expert but here are my thoughts.

How are your fuses? What about the engine side relays?

Can you find another switched 12V system and check it? Does the OBDII dongle power on and take a connection?

On my 2007 LY2 pink and red are power. I believe red is switched 12V with pink coming off of relays and the computer for the injectors and coils. Find one coming forward from the firewall and check it with a multimeter and the engine block, when the key is on you should get 12VDC. If you do, move down the line to your relays and grounds. If you don't, move upstream to find why the key isn't closing that circuit.

Edit: Pete is correct that OBDII should be hot and should let you know if your computer is getting turned on. If you don't see RPM, your computer won't deliver fuel and spark.

Datalink connector SHOULD be wired to constant hot, not switched.  If they didn't bother to wire in a check engine light then who knows how they did it.

I'd grab a scantool if possible and check first of all to see if the computer wakes up, and then if you can communicate, and then look for an RPM signal while cranking.

I thought I read somewhere that the VATS can shut off fuel and spark?  It only does spark?

So, my stepfather and I don't 100% get along, so I mostly tried to stay out of his way and help where he could while keeping an eye on what he was doing.  As a result I'm not fully clear on what steps he did and in what order.

He went through the fuses, and we checked the fuel pump relay.  With key on we found 12V across the terminals (85 and 86? I think?) but when we replaced the relay we still didn't have the pump turning on.

We hooked up a scantool, it worked with key on and key off.  With key on it gave a live view of what was going on.  Fuel and spark were both listed as OL (out of limits? offline? not sure what the scantool translated that too) but it gave a couple values that I checked and were good (air intake temp was at ambient, stuff like that, didn't think to crank it to see if RPM showed up.)

If everything is getting power and ground correctly, I'd be looking at the crank sensor. Make sure you're seeing RPM on the scantool. (I had an issue where the signal pin backed out of the connector so a new sensor gave sporadic rpm signal)

I'm also a little confused on the genesis of the issue. Had this motor been running in the elco and then just randomly went kaput? Or is he finishing a swap started by someone else?

Again it has been a while.  Fuel pump will prime even with a VATS mismatch, and the engine will run for a half second or so before it cuts spark and fuel.  So, I really do not think this is the issue.  (I say this with authority, as I was cranking an LQ9 swap to build oil pressure and such, before going in and disabling VATS, and the engine fired up.  Much to our surprise!)

85 and 86 are the relay coil circuits.  If you have 12v on both while cranking, then the computer is not trying to engage the fuel pump relay.  The relay coil is the load in the circuit, you should see ground on one of those when you are cranking.

30 and 87 are the switched side of a relay.  GM usually wires the relays "backwards" with 87 as the power in and 30 as the power out to the pump.  They then leave a jumper wire in the harness connected to 87a, so you can manually power the pump through the NC side of the relay.

No spark AND no fuel pump makes me think no RPM signal.

I'll leave the relay stuff to Pete, he seems to know his relay wiring, and just second the recommendation to check for RPMs when trying to crank. No RPMs = fuel/spark and this could come from the crank and/or cam sensors. 

Like iansane asked, was this engine running in the car? If so, sounds like a poor connection. If not.... Good luck. 

In reply to iansane (Forum Supporter) :

Yup, it ran previous to this.  Ran for a couple years at least.  Ultimately not sure why it crapped out but when it did he was able to trace it to not having any spark.  Fuel appears to be a new thing though.

In reply to Pete. (l33t FS) :

There was 12V across the terminals with key on, engine off.  So there would be power at one side and ground at the other.  I'll ask him to check out the RPM signal while cranking.  Sounds like you're saying we can guarantee there's power to the pump by jumping terminals?

I do LS swaps for a living. From what you're describing, I'd check the pink wires at the coil bank connectors for 12v+ while ignition is on. You'll have a single pink wire at each coil bank connector, should be full time 12v+ hot while key is in run position. Also the pink wire running to each injector must have full time 12v+ while ignition is on. Both of those circuits should be on 10-15 amp fuses. I'd first look for a blown fuse if no 12V. As far as "VATS", or antitheft, that should've been turned off in the ecm during the reflash by whomever did the initial LS swap

I'll let him know to check those points out, thanks.

I've heard that the ECM can forget it has been flashed and revert to factory, ever run into that?

In reply to Mr_Asa :

No not really. The ecms usually just go bad. Whomever did the swap should've put a minimum of 4 fuses somewhere in the harness- one for coils, one for injectors, one for full time ecm 12v+, and one for ignition on 12v+. My first plan of action would be to locate those fuses. Could be under the hood, under dash, but if it was any sort of competent installation, those fuses should be there. 

Aeromoto said:

In reply to Mr_Asa :

No not really. The ecms usually just go bad. Whomever did the swap should've put a minimum of 4 fuses somewhere in the harness- one for coils, one for injectors, one for full time ecm 12v+, and one for ignition on 12v+. My first plan of action would be to locate those fuses. Could be under the hood, under dash, but if it was any sort of competent installation, those fuses should be there. 

Doesn't sound like it was very competent if there's no MIL

Based on what I saw of the wiring, I'm going to lean towards incompetence as well.  Relays aren't labeled, color of the wires is the same, no grommets in a few positions where it has to pass through the firewall.  I'll mention the fuses for those circuits and see what can be found out.

I'm going to recommend this one time.  Have him go to ebay and grab a standalone harness for his combo, remove all the wiring the other guy did, and plug it in and go with no more hunting for what the last guy did wrong.  $300 will save so much headache.  I just had one delivered for the 57 not because I cannot modify one to standalone, but because my time is worth more than harnesses cost now.

Like this one? https://www.ebay.com/itm/1997-2006-DBC-LS1-STAND-ALONE-HARNESS-W-4L60E-4-8-5-3-6-0-VORTEC-DRIVE-BY-CABLE/324104463795

I'll recommend it, but I kind of think Mom is a little frustrated with this.  

Ok guys, bumping this again.

Mom is a little frustrated with this.  She us ready for it to be done, and ready for it to be taken to a shop.  Do I remember that there was a GRMer in Orlando that had a shop that specializes in LS swaps?