LS Swap, engine runs 30 sec and dies. PLEASE HELP!!

[69CapriceHDTP]

So finally completed my swap tonight. Fires right up and runs amazing, 30 sec later it dies like you shut the key off. Turned key off and back on and you cant hear the fuel pump cycle. Checked fuse and its good. Made jumper wire from fuel pump to constant hot wire and fuel pump works. So I tried starting it but coil pack power was lost. No clue. Disconnected battery for 5 minutes, touched leads together quick and then hooked it back up. Reconnected fuel pump wire like it should be and turned key to on, fuel pump cycled like it should. Turned to start and the car ran amazing again for about 30 sec and died. Key was cycled countless times before we even fired it up and had fuel pump cycling every time, now it does not.
Vats has been removed as well.

Any ideas would be greatly appreciated! Thanks

[parsonsj]

You're sure about VATS? That's a classic VATS scenario...

Can you give us more detail? What engine? What engine controller? What kind of fuel pump? How is the fuel pump connected?

[garrett68]

Check your ground on your engine harness. I had the same scenario with my fuel pump relay. I have a psi harness. The fuel pump relay gets its ground through the ground on the engine harness. Hope this helps.

[Vegas 69]

ECM Ground and VSS wires connected.

[69CapriceHDTP]

Vats on hp tuners says none and a Vats issue will make them fire and die right away. My harness is pickup harness modified by S&S using stock ECM, came with its own separate fuse/relay box as well where fuel pump relay is at. Engine harness grounds to back of engine on the block. ECM ground grounds to bolt I put on firewall with paint ground off underneath, where bolt runs through firewall I also ran ground wires from there to engine ground location. Only wire not hooked up at the moment is TCC wire as I need to wire in new brake switch. I'm going to run a ground strap from engine to frame right now, but engine has solid mounts anyways so its all metal to metal. 6.0/4L80 combo

[69CapriceHDTP]

UPDATE. Ran ground from bell housing to frame and car started and ran for well over a minute and then died. After it died the fuel pump shut off the 3 seconds after. Numerous times after the fuel pump always turns on and always starts. This last time I just adjusted the fuel pressure regulator to be at 65psi for start up and 55 while idling. Ran 20 seconds and then died, now back to no fuel pump.

[willieboy240]

Buy, borrow, steal, a hp tuners and record data. I bet you have a bad or misdialed sensor. Two sensors come to mind like a Tps or o2.

[99sslsone]

Hey there, I know this is an old thread, but I am experiencing almost the exact same issue as you with my LS swap. I'm very curious if you ever figured anything out? I'm pulling my hair out. Thanks in advance, I'm REALLY hoping and praying to hear back. Thanks.

[Snowcatter]

You are positive VATS has been removed from your ECM? You have ensured good ground to your engine? Fuel pressure gauge hooked up to verify good pressure once engine fires? Properly wired ignition switch? Do you have a diagnostic scanner to see what codes are being thrown?
It sounds to me like the fuel pump control is not configured/wired correctly. If fuel pressure is present when engine fires it will run for approximately 30 seconds before fuel starvation causes it to shut off.

[Zachalanche]

Any codes? I had a similar issue years ago, and it was throwing a cam position error. Turns out i had the wrong cam gear (1 sensor tooth instead of 4). Probably not the same issue you are having, but maybe thrre is a code to help guide you

[99sslsone]

I'm not sure about OP, but in my particular case, yes I am sure VATS has been turned off. It is a 5.3 4L80E swap vehicle. Professional harness conversion and tune from LSX Specialties. It has been a running and driving vehicle for about 8 months, though I've only put around 50 miles and half a dozen trips on it. I have checked and cleaned my grounds and battery connections. Verified ignition 12v before, during, and after cranking. All fuses are good. Relays are good even though I replaced them with new anyway. Key in "ON" position powers ignition relay and powers key-hot side of fuse box, but P59 ecu will not trigger the fuel pump. The LSX Specialties harness utilizes a single ground connection, which by the ignition relay activating proves it is a good connection. I can remove the FP relay and jump the relay socket no problem, proving all fuel pump wiring is good. When doing so, fuel pressure gauge shows a steady 58psi. When I crank, I have no fuel pump, injector pulse, or spark. I also have no DBW pedal activity, even though I can hear the TB energize when I key on. I had LSX Specialties supply me with a replacement ECU and base tune, only to fire and run perfectly for 30-36 seconds, die and show same exact symptoms. While running it shows 58psi fuel pressure. There are no DTCs except O2 sensors, which I have had removed for wideband tuning and been running previously. If I connect HPTuners and rewrite my tune the FP relay and pump audibly comes back to life and the truck will run for exactly 30-36 seconds before it shuts off same symptoms. No pump, no injector, no spark, no dbw throttle activity. I reload the tune, boom FP relay and pump run as they are supposed to with key cycle, throttle blade moves with pedal, truck will start and run great. For 30-36 seconds and then same thing. Nothing will work again until I reload my tuneup onto the ecu with HPTuners. When the truck dies after 35 seconds it is like I turned the key off. No hesitations or stumbling like it's running out of fuel or misfiring, no warning, just off. I've had 2 ECUs now do the same thing. Only 3 things on the truck that have changed since it ran and drove last were that I connected my torque converter lockup wire as directed to my brake switch, I replaced the seats in the truck, and I replaced the door speakers. I have since disconnected the TCC wire, and unplugged the new seats (airbag/weight sensor). I left the speakers connected, but I have tried pulling the radio fuse with no change. I am extremely lost and devastated and praying someone has insight. Thanks.

[protour_chevelle]

VATS wont let an engine run for a minute then die. Vats will allow the engine to fire for up to 5 second then die.

Is the ECU hard mounted or just hanging out? Ive seen stock ecu swaps that need the case of the ecu grounded due to poor grounding elswhere. Car would run, ecu would wiggle around and engine would shut off.

[99sslsone]

The ECU is hard mounted to bare metal under the dash.

[cutlass11]

Not a Vats issue!!!! #1 I would double and triple check grounds #2 I would check the crank or cam sensors on your engine. based on the info I would bet on a sensor issue. but you should also get a code UNLESS the code has been set to be disabled by the tune (I've seen it happen). it could be a the wires to one of the sensors installed incorrectly/backwards. #3 I would go pin by pin and confirm the harness is pinned correctly with a pin out chart (LT1swap.com) and then check the wires at the sensors. The common sensors that will cut the engine are cam and crank. #4 I would check the tune and look at the crank senor reluctor teeth.

Again I'm betting on a senor issue either a bad sensor or incorrectly wired. good luck

[cutlass11]

sounds like a sensor issue

[cutlass11]

#1 I would triple check grounds
#2 I would check or even replace the crank and cam sensors
#3 if problem persists I would check pin by pin the harness at the ECM to make sure its correctly pinned and also at the sensors
---- I'm betting on a sensor issue/ wire issue but no check engine light??? hmmm.... definitely not Vats. if you check the fuel and its good, the two other sensors that will shut off the engine is crank and cam.
#4 check the tune!!!!!!! I know its been said look at VATS and column lock and there is also a crank relearn procedure.




I just re-read the post.... seems light you are on the right track. so you have to re load your tune to get it to run for 30 sec and the it dies and will not start until you re load your tune again??? am i read that correctly??? hmmmm SO is the ECM not holding the tune but is been replaced. i would try the replacing the sensors would be an easy way to rule them out.

[cpd004]

Correct me if I'm wrong, but a rewrite also clears DTC's. Did you alter those at all since it ran for longer than 30 seconds? Also, is there anyway there was some sort of wiring damaged under your carpet from the seat swap?

[csouth]

This thread got bumped because the user in post #8 asked a question instead of starting a new thread. I think you guys are wasting time until he starts a new thread...

[99sslsone]

Just wanted to update this and not leave a cliff hanger for my particular case. I understand I posted in an old thread instead of started my own, however I was just hoping to hear from the OP.

I was able to figure it out. The calculated manifold absolute pressure sensor maximum and minimum tables needed adjusted. Being in Speed Density, when the engine would fall outside of the range, die, and set a P0106. I would like to thank user cpd004, I wasn't catching the DTC at first by reloading the tune essentially clearing the code. All is good now, thank you.