Need help troubleshooting.

[Tirebite]

I completed a swap back in March on my truck. I had a 4.3 in my 94 RCSB and replaced it with a 5.3 from an 2005 Tahoe. My truck died on the way to the lake to take my daughters tubing on our boat. When I was going down the on ramp to merge onto the interstate, the engine fell on it face and would not accelerate. It made a weird thump sound when I tried to pedal it as if it had no fuel. I pulled over and let it idle and the idle got real low for a couple of seconds and then seemed to be fine. I got out and let it continue to run while I looked over the engine and trans. I shut it off to go talk to the vehicle that was following me. I came back to start the truck and it would not start. It turns over fine and sounds normal trying to start but will not fire up. I towed it back to the house. It just turned over 1000 miles since I completed the conversion and has been running and driving amazing.

I had a digital battery charger hooked up to recharge the battery after draining it from trying to get it to start. The battery has 13.8 volt in it but the charger says it has an internal short in the battery? Would this really keep my truck from running?

All the injectors have power and so do the coil packs. I pulled the spark plugs and verified that they are making spark. I am getting fuel to the rail but I don't know what the pressure is. Any ideas or advice as to what I should be looking for.

 

[96Z71ECSB]

You've probably fixed it already but I'll give my input anyway.
Change the battery and you should be good to go.
The ECM will shut itself down if it detects a short in it's power supply (battery). I believe it does that to protect itself.
I've never run across that type of behavior with GMT400's but I have on other vehicles.
Install a new battery and the ECM should be happy again.

Good luck!

 

[Tirebite]

The battery is good to go. I suspect that my fuel is not supplying the needed amount do pressure to push through the injectors. I am still trying to locate a pressure test kit to confirm this.

 

[badazzbulldog]

did you do a new pump when you did the swap? I would say the 4.3 tbi pump isnt pushing the pressure you need

 

[Tirebite]

Bought a pressure tester and was only getting 5 psi to the rail. Went and bought a new high quality Airtex 255 pump and she fired right up and is running just like before. Guess that's what I get for buying the cheap pump to run this LS engine, only lasted 1027 miles.