5.3 Swap Starts then Dies

[angelm_ix]

Hey all. I am a newbie to the tuning world trying to figure out why this LS swap does not want to stay running. It is a 2007 LMG going into an '81 C10. All that has been done to it is shorty headers, intake manifold, and aftermarket intake. I used a new PSI harness. I have disabled VATS, taken out some DTCs, and set my oil pressure minimum to 0 because I had it disconnected for my Dakota Digital sensor instead. I have since plugged in the original sensor but still nothing. Fuel pump has 12v run and start. I have done Gen III swaps before, but this is my first Gen IV. I just do not know what else to check. I have attached a log file below. You guys know way more than me so I would be thankful for your help. 1981 C10 5-6-24.hpl

[gtstorey]

Need to post the tune also.

[edcmat-l1]

Need a fuel pressure gauge on the vehicle at all times. Preferably one you can view from the driver's seat while operating the vehicle.

You need to add injector pulse width to your pid list.

And you also need to try and keep it running with throttle input. It's possible the idle air is too low, or it's too rich, and if you can keep it running by cracking the throttle it may come around for you. Get it to light off, try to keep it running, and if you can, try slowly letting off the throttle while still keeping it running.

And the voltage is showing extremely low. I saw as low as 8.8 volts. Need to get a charger on it. I'm surprised it fired up.

[angelm_ix]

Need a fuel pressure gauge on the vehicle at all times. Preferably one you can view from the driver's seat while operating the vehicle.

You need to add injector pulse width to your pid list.

And you also need to try and keep it running with throttle input. It's possible the idle air is too low, or it's too rich, and if you can keep it running by cracking the throttle it may come around for you. Get it to light off, try to keep it running, and if you can, try slowly letting off the throttle while still keeping it running.

And the voltage is showing extremely low. I saw as low as 8.8 volts. Need to get a charger on it. I'm surprised it fired up.

Yes I did that log on my 10th time attempting to start so the battery got a bit low. Throttle did nothing when it fires up. I also have a fuel pressure gauge on the fuel rail I was looking at while someone was starting it. It is at 58-60psi while starting and when it fires up. I will post another log with injector pulse in it and my tune later today.

[angelm_ix]

Need to post the tune also.

Sorry I will post a tune and another log later today.

[Alvin]

Hey all. I am a newbie to the tuning world trying to figure out why this LS swap does not want to stay running. It is a 2007 LMG going into an '81 C10. All that has been done to it is shorty headers, intake manifold, and aftermarket intake. I used a new PSI harness. I have disabled VATS, taken out some DTCs, and set my oil pressure minimum to 0 because I had it disconnected for my Dakota Digital sensor instead. I have since plugged in the original sensor but still nothing. Fuel pump has 12v run and start. I have done Gen III swaps before, but this is my first Gen IV. I just do not know what else to check. I have attached a log file below. You guys know way more than me so I would be thankful for your help. 1981 C10 5-6-24.hpl

I've run into this a couple times on GEN 4 swaps.

traditionally a engine will run without a cam sensor. They just might not start every time.. but every other time they will start.

A GEN 4 is not like this.. If the cam sensor wiring isn't correct than it will fire and immediately shut back off. It acts like a VATS issue. The confusion comes from (IMHO) that the sensor pinout has two wires swapped in the little jumper harness that is mounted on the timing cover to the cam sensor. Some guys take their engine harness right to the cam sensor without this jumper harness. Sometimes the pinout is just wrong itself. But this WILL cause this start and immediately die situation. IT WILL not throw a cam code while doing this.

This is a pain to diagnose because there is nothing pointing to this as a cause.. But go though that wiring carefully from the ECM, to the jumper harness on the timing cover, to the sensor. Be mindful of the pinout and how it changes in that jumper harness.

[Alvin]

See this link for more info

LS2_Cam_Sensor_Wiring2.jpg

[angelm_ix]

Here is the tune and a new log file. Battery still seems a bit low but it should still work. It sounds very strong when it does start for that second or two.

I've run into this a couple times on GEN 4 swaps.

traditionally a engine will run without a cam sensor. They just might not start every time.. but every other time they will start.

A GEN 4 is not like this.. If the cam sensor wiring isn't correct than it will fire and immediately shut back off. It acts like a VATS issue. The confusion comes from (IMHO) that the sensor pinout has two wires swapped in the little jumper harness that is mounted on the timing cover to the cam sensor. Some guys take their engine harness right to the cam sensor without this jumper harness. Sometimes the pinout is just wrong itself. But this WILL cause this start and immediately die situation. IT WILL not throw a cam code while doing this.

This is a pain to diagnose because there is nothing pointing to this as a cause.. But go though that wiring carefully from the ECM, to the jumper harness on the timing cover, to the sensor. Be mindful of the pinout and how it changes in that jumper harness.

My PSI harness came with the connector to plug straight into the cam sensor. I checked the wiring with a multimeter to the ECM and everything is correct. Pin A goes to Pin 44 (5V Ref) at the PCM, Pin B goes to Pin 66 (Low Ref) and Pin C goes to Pin 64 (CMP Signal). I checked this with an Identifix wiring diagram for the VIN of the engine/ECM.

What's odd is that, when I plug the ECM back in and turn the ignition to on, Pin A of the CMP connector gets 2.6V and Pin C is getting 5V. Shouldn't Pin A (5V Ref) get 5V when ignition on? And is Pin C (CMP signal) supposed to have 5V?

Sorry if all that sounds confusing. I am confused myself.1981 C10 5-7-24.hpt1981 C10 LOG 5-7-24.hpl

[Alvin]

Here is the tune and a new log file. Battery still seems a bit low but it should still work. It sounds very strong when it does start for that second or two.



My PSI harness came with the connector to plug straight into the cam sensor. I checked the wiring with a multimeter to the ECM and everything is correct. Pin A goes to Pin 44 (5V Ref) at the PCM, Pin B goes to Pin 66 (Low Ref) and Pin C goes to Pin 64 (CMP Signal). I checked this with an Identifix wiring diagram for the VIN of the engine/ECM.

What's odd is that, when I plug the ECM back in and turn the ignition to on, Pin A of the CMP connector gets 2.6V and Pin C is getting 5V. Shouldn't Pin A (5V Ref) get 5V when ignition on? And is Pin C (CMP signal) supposed to have 5V?

Sorry if all that sounds confusing. I am confused myself.1981 C10 5-7-24.hpt1981 C10 LOG 5-7-24.hpl

The problem is PIN A B C are swapped around in that jumper harness that a lot of GEN 4's come with. The pinout to that connector could be correct..but is it changing or should it change though that cam jumper harness.

I'd call PSI and make sure they mean for your cam sensor harness to plug directly into the cam sensor or should it plug into the jumper harness that some have on the timing cover. I'd spend a lot of time looking at this.. This really looks like the cases I've ran into.

[blindsquirrel]

Wouldn't a msising CMP still leave it with only a 50/50 chance of guessing #1 TDC, and at least occasionally it would guess wrong and give a long crank or popping/banging and a no-start? Even if the older default strategy where they run normally after guessing the correct #1/#6 TDC no longer applies?

[blindsquirrel]

E40 and earlier have this in the manual:

If the crankshaft position (CKP) pulses are lost the engine will not run. The loss of a camshaft position (CMP) signal may result in a longer crank time since the ECM cannot determine which stroke the pistons are on.

By 2009 that language is gone.

The ECM also uses CMP sensor output information to determine the camshaft relative position to the crankshaft, to control the CMP actuator if equipped, and for limp-home operation.

...meaning that unlike the older stuff the engine will continue to run if CKP is lost.

[angelm_ix]

On my valley cover, there is an oil pressure sensor and another sensor next to it. I think it is another cam sensor. The harness did not have a connector for this sensor. Would this cause an issue with starting?

[blindsquirrel]

On my valley cover, there is an oil pressure sensor and another sensor next to it. I think it is another cam sensor. The harness did not have a connector for this sensor. Would this cause an issue with starting?

Does it look something like this?

screenshot.07-05-2024 15.45.48.png

[blindsquirrel]

Your tune file has all the DOD bullshit still turned on.

[angelm_ix]

Your tune file has all the DOD bullshit still turned on.

You're absolutely right. I was told this engine didn't have that. I'll turn it off and report back.

[edcmat-l1]

Cam and crank sensors both should have a pid. Might want to add them and log it.

Best would be to scope cam sensor but that would require an o-scope.

[angelm_ix]

I deleted DOD and still the same. It's sounds so strong and healthy when it does turn on. Just wish it stayed on.

Here is the tune with a new log on it. Not sure if these PIDs are the ones I should be using for cam and crank. Thanks for your help.

1981 C10 LOG3 5-7-24.hpl1981 c10 DOD delete.hpt

[Alvin]

Wouldn't a msising CMP still leave it with only a 50/50 chance of guessing #1 TDC, and at least occasionally it would guess wrong and give a long crank or popping/banging and a no-start? Even if the older default strategy where they run normally after guessing the correct #1/#6 TDC no longer applies?

That's what I said... traditionally yes.. but on gen 4 it might not. I've had more than 2 now act like vats issues and it is where the cam sensor wiring was off. No cam codes. It will fire and immediately shut off. One was from a guy who plugged a GMPP cam sensor plug right into the sensor and did away with the jumper harness. I keep saying it.. maybe people will take some time to look.. but that jumper harness has wires switched in it.. A,B,C might be C, A, B or whatever.

[edcmat-l1]

That should be the right pid and damn sure it don't move. Looks like Alvin called it.

Does your meter have a frequency setting? If you don't have a scope you still should be able to check the signal return with a meter on the frequency setting. You could probably even check it on your volts setting although that would probably just average it.

[edcmat-l1]

That's what I said... traditionally yes.. but on gen 4 it might not. I've had more than 2 now act like vats issues and it is where the cam sensor wiring was off. No cam codes. It will fire and immediately shut off. One was from a guy who plugged a GMPP cam sensor plug right into the sensor and did away with the jumper harness. I keep saying it.. maybe people will take some time to look.. but that jumper harness has wires switched in it.. A,B,C might be C, A, B or whatever.

100% right. That little jumper is actually an adapter.