Ellistuner

Hey guys, new to the forum and have been researching this problem and I can't figure out what is wrong.

I am swapping a Gen III, 5.3l engine and 4l60e transmission into my 1948 Chevy truck on an S10 frame. I actually had this engine running before I added the radiator and relocated the battery. Now it won't start.

Here is what I can verify:

Have 50 psi at the fuel rail
Have power to coils and injectors - I used a noid light on the coils and a LED test probe on the injectors and both have power during crank.
Will fire on starting fluid
Limited 2 sec crank (i have another pcm with the 12587906 os and it allows me to have an extended crank but still no start - I think this means my sensors are ok?)
New crank sensor
New cam sensor
OBDII codes - right now it shows P1637 and P1638 along with a couple of EVAP codes because I have not deleted them from tunerpro.

I don't think it is a VATS issue because I verified they are deleted in tunerpro. I flashed the PCM using LS Droid.

What am I missing here? It is clear the PCM is not giving ground to the injectors but why?

Can you help? I am desperately trying to get this to run. Super frustrating.

Thanks in advance.

Ron

B52bombardier1

Did the injectors sit for a long period of time with ethanol pump gas fuel in them? If yes, the injectors might be mechanically stuck closed.

Rick

Ellistuner

Thanks Rick for replying. The injectors are new but it is possible I had some bad gas from the old S10 tank I will pull them and see if they look bad.

What I am thinking is the PCM is not giving the ground to fire the injectors and I don't know why.

Anyone know why the PCM would not give the ground in my case?

Old Buzzard

"Have power to coils and injectors - I used a noid light on the coils and a LED test probe on the injectors and both have power during crank."
bassackwards on the test tools.
Does the noid light blink when plugged into the inj plug?
Yes = injector issues.
No = issue between inj plug and pcm.
Fuses good?
ALL grounds hooked up and tight?

Ellistuner

Thank you Buzzard for responding. I will try the noid light on the injector but I did not have a blink on probe when plugged into the injectors during crank. Seems I need to check the wires to the pcm and see if I have a problem there.

I did check all of the fuses and grounds. But will check again.

Thanks again for the suggestions.

One thing to add, I had to recharge the battery having died from trying to get the engine started. Upon full charge, I have an extended crank instead of the limited 2 second crank as before. Another clue perhaps?

Old Buzzard

"One thing to add, I had to recharge the battery having died from trying to get the engine started. Upon full charge, I have an extended crank instead of the limited 2 second crank as before. Another clue perhaps?"

Excessively low batt power could mess with the injs working.
I have tested down to about 9v and saw some erratic firing issues on the scope traces.
"and relocated the battery".
Suggest a volt drop test on the + and - sides of the battery.
If you are using the frame as a ground, you may have significant volt drop.
Watch your scanner for voltage reading while cranking. Should read in the 13+'s before cranking. Wouldn't want to see more than about a volt/volt and a half drop while cranking.
Be sure the engine is WELL grounded to the frame if this is the case. Volt drop test there, too.

Ellistuner

Great suggestions. I will check the volt drop when I get a chance.

I am using the frame as the ground from the relocated battery. Would it be advisable for me to run a cable from the negative post to the cylinder heads as grounds?

ls1nova71

iTrader: (4)

I would. You can't have too many grounds.

Old Buzzard

A volt drop test tells the tale.
I always do both. To the frame and to the engine.

Ellistuner

Old Buzzard - for clarity, do you run two leads off the battery? One to the frame and one to the engine?

I currently have two grounds running from the heads to the frame on each side of the truck's frame.

Thanks again for your input. I really do appreciate your help.

gagliano7

I ran battery to frame and engine to frame on my 1992 silverado swap. I also have ground from firewall to head and block. On my 5.3 there is a ground bolt on the block by the cam sensor. My swap has been running since 2011.

Ellistuner

I have been slammed this week but last night I tested the injectors with the noid light this time and don't get any blink, or light for that matter, during key on or crank. I will chase down the wiring to the pcm and see if I have a problem with a faulty wire or ground.

Thanks again.

gagliano7

They are hot all the time and the pcm controls the ground to fire the injectors. I would check to see if you have 12 volts with key on for the injectors.

Ellistuner

Good call. I have not checked that yet but will tonight and report back. Thanks for the advice.

Old Buzzard

The noid light does not light until it sees a ground pulse.
Chek for 12V with a test light or DVM.

Ellistuner

I was able to get a multimeter on it this weekend. I do have 11.75v at the injectors when key on and during crank.

Still no noid light illumintation. I am now thinking I have a bad wire somewhere between the injectors and the pcm. Does the pcm use only one ground for both sides, or does it have multiple grounds for the injectors?

rpturbo

iTrader: (47)

There should be 2 grounds, one on each side that originally went to the back of each cylinder head.

Ellistuner

I am still stumped. I did some more work on the truck this weekend. I took the green and blue harness connectors apart to check all of the pcm's grounds. I ran a test light from 12v to each and every ground on the pcm harness and have light on every one. Yet, still no start.

Any clue what is going on? I am desperate.

Thanks in advance.

rpturbo

iTrader: (47)

I know you say you verified vats is off, but do you have anything you can either stick that ecm in that you know runs, or vice versa, pull a known good ecm and try it?

Ellistuner

That is a great suggestion but I don't have another vehicle I can stick this pcm in to test and I don't have a good working VATS deleted pcm from another vehicle. This is my first build.

Correct me if I am wrong, but the reason why I don't think it is a VATS issue is I had this running at one time using the same pcm. I relocated the battery to the truck bed and have not been able to get it started since. I do have another pcm that I have hooked up just to try and it does the same thing. Crank no start.

What I don't know, and forgive my ignorance, is: can VATS get re-enabled if disconnected from power for an extended period of time? That seems illogical to me if the VATS were deleted in the flash memory but you never know.