4.3 to LS1 swap won't crank
 

2003 Silverado, originally a 4.3/4L60E, drove into my shop with no known issues.

Donor car was a 2000 Z28 with a salvage title that just broke the rear end at the drag strip, was a running/driving 11.7 car in the 1/4....heads/cam LS1 with a TH350 or TH400, i don't recall.

Owner wants the Camaro's driveline put in the truck. I got a 03-05 engine harness, modified it to fit the car engine/accessorie. i didn't cut/splice any wires in the process with the exception of having to add pigtail connectors for the TPS and IAC as well as fixing a broken crank position sensor.

As far as i can tell, all the wiring is correct, fuses are all good, and relays appear to good too. I swapped the IGN and Starter relays with a couple others just to verify those weren't the issue.

At key-on, everything lights up as it should but i notice the gauges don't appear to work. the coolant gauge is pegged all the way to the right, but i cannot be certain it wasn't like this before i got the truck anyway. I put 5 gallons of gas in it but the fuel gauge doesn't move either.

I've moved everything from the Camaro tune over to the truck's ECM, disabled VATS and everything. VATS shouldn't even matter as its the truck's original computer, but i disabled it for good measure. I haven't tested the starter wire yet, the truck is now sitting outside and it's dark and windy, so i'll try that tomorrow.

Any ideas why it won't even crank? The truck and the camaro both drove right to my shop with no issues (minus a broken 10-bolt in the Z28).

Missing ground on back of block

Nope that's all there.

I was just thinking about it and realized I didn't wire in the neutral safety switch yet. The camaro was originally a M6 car, and I forgot I was using a 4l60 truck harness in a truck that had a 4l60 in it....I came in the house and saw the shifter box sitting on the table and realized what I'd done, or not done rather....im going to get after it tomorrow.

The gauges not functioning correctly sounds like a ground issue.

I had this happen recently. Found a mouse chewed through rear ground on passenger side rear of block. It had a No crank condition. No gas gauge on cluster. Some of the other parts of cluster not functional.

Pictures of the rear grounds for reference.

https://cimg3.ibsrv.net/gimg/www.per...258ea6894a.jpg


Passenger side rear of block engine harness ground.


https://cimg4.ibsrv.net/gimg/www.per...464520ecec.jpg


Driver side rear of block engine harness ground.

Ok, i'll check grounds but i think they're all good.

I really need to know what wires i need to jump for now, then can hook up to the neutral safety switch when i install the TCI shifter. The range selector plug was cut off the harness apparently, i found the wires tied up in the loom, i never noticed it was missing and didn't think to look since this has a non-electronic transmission. I've looked at every wiring diagram i can find and none make sense. Does anybody know which of these wires i need to run to the NSS?


https://cimg6.ibsrv.net/gimg/www.per...d4f1fd4dd3.jpg


https://cimg7.ibsrv.net/gimg/www.per...b669e7f82c.jpg

Got the NSS wires figured out..dk grn wire crossed with pink, white and white/black are grounded....truck cranks but cranks really weak, like it has a bad battery, and won't fire...battery is brand new. Starter relay is good. Fuses are good. If I jump the relay, it cranks over like crazy.

What could be the problem?

Sounds like the relay might be your issue. If not, have the battery checked. Maybe it's week under load.

Tried 2 other good relays, same results. Battery is brand new, other battery WAS bad, but new battery produces same results.