Kamaro

Hi guys,

I just swapped a LS3 based 416 motor into a '71 Firebird, and I used the GM LS3/525HP controller kit (19259261). when I crank the engine it would fire up but will shutdown after about 1 second, just like if VATS is active!, I read in the engine controller kit manual that this ECU has no VATS and the engine should fire right up. I know this engine is not stock, but it should at least idle (even a sign that it tries to idle!), but it looks like the ECU would shut it off shortly after its fired up. I connected the scanner and it show any DTCs. Any hint/tips/ideas?

Project GatTagO

iTrader: (7)

Was the engine built with a 58 tooth reluctor? Did you use the correct 4 point cam gear? What the fuel pressure?

Andrew

Kamaro

The crank has a 58 tooth reluctor wheel and I do use a 4 point cam gear, I'm not sure about the fuel pressure (no gauge), but I saw a good fuel pressure when I cracked open the fitting connected to the fuel rail.

I feel that its shutdown by the ECU, because everytime I fire it up it will shutdown after exactly 1 second.

aknovaman

iTrader: (7)

You likely have air in the fuel rails. Prime it a ton with a squirt bottle full of gas or do the same thing and a can of starting fluid. Even if you cycle the key several times and repeatedly cycle the fuel pump, at startup the prime pulse and normal injector pulse is too small to purge the air from the lines and rail.

Keep trying and it will purge.

ctsvcaddy

iTrader: (2)

Is your fuel pump controlled by the ecm through the engine harness? I would try wiring the pump hot at all times to eliminate the fuel side of the equation.
What regulator are you running, fuel pressure has maintain at least 50 psi to run? It also possible the injector data in the ecm is so different than your current injectors that it won't run.
After verifying fuel I would take the ecm to a reputable tuner and have them put in a similar program to what you are running. Most good tuners have a database of the cars they've done and can match you up with something to get it running.

1989GTA

Are you getting any codes?

bczee

iTrader: (12)

Check to make sure the battery and the Ign 12+ battery stays hot as you go from off - run - start - run.

Too many use an acc Ign battery that will cut out as the key is cycle .

BC

Kamaro

I tried to prime the pump through a direct 12v to the pump for few seconds then squirting out the fuel through the fuel rail many times until there was a stable stream of fuel, I also checked the fuel pressure and it was a steady 60 PSI all the time, I even tried to start it up while sending a direct 12V to the fuel pump (by-passing the ECU F/P relay) and it didn't do any difference. I think now I elminated any problems related to fuel delivery, so it seems its related to something else. Is it possible that my ECU is still locked by VATS?, it shouldn't because its part of a LS engine controller kit and not from a donor car. I don't have access to any good tuner around my area, but I do have a HP tuners box and got a license to access the ECU if anyone got any hint for modifying the stock file. I just checked the scanner again, and no codes has been found.

aknovaman

iTrader: (7)

Does scanner show rpm during cranking? If not the Crank position or cam position sensor may not be plugged in all the way.

Kamaro

I just checked that and found that its not reading RPM, I also checked both the crank and cam sensor plugs and they seem fine. Is it maybe because its a new crank (non GM), that may need to do a re-learn for it?

jcvett56

It would still fire even if you didn't do a crank learn. It would just throw a code after it starts. If you have HP Tuners just do a read on your ECM with everything hooked up and check to see if VATS is disabled or not and that should answer your question instantly.

IF you aren't experienced with HP Tuners and don't know where to disable Vats then look near the Left Most area and click on 'HP'. Then Disable VATS 1, 2, and starter checks.

jcvett56

Are you also using LS3 MAF, or MAF the file is based off of? If not that can cause issues with starting but still isn't the issue with your RPM not showing up.

Check your KEY switch and make sure it's wired properly for your swap, an easy check is to see if check engine light stays on during crank.

Project GatTagO

iTrader: (7)

He is using a GMPP kit, so there is no VATS. If the engine fires but dies after a second, then he has the ignition switch wired properly. If the ECU was not getting power during cranking, it wouldn't fire at all.

Andrew