1995Cam

hello everyone! I have just completed a rebuild on a 1995 LT1. After I finished install engine started right up but will only run for a few seconds then shut off. I can turn the key in the off position and restart and it will for only another few seconds. seem like fuel is shut off. It 's like its gets primed but after that it shuts down. Everything on the car is new all sensors, vacuum hoses, everything! will the ECU shut it down with the mods ive done?
30 over
stage 4 cam
is about it!
any help would be greatly appreciated!

Injuneer

Has the PCM been reprogrammed for the stated modifications - particularly the "stage 4" cam?

Have you checked the fuel pressure? Have you scanned it for codes?

1995Cam

no reprogramming has been done, I figure it would atleast run to get it to the stop to do that. fuel pressure is good, just seem like to shut off power to the injector until you restart it. its starts just fine but after 2 second its like you shut the key off.
where I'm, at I can't find anyone to program it or has the ability to do so, unless I load it up.
I have not scanned for code.
what do I need to do? first?

Injuneer

To scan a 95 you need an OBD-1 scanner, with a 12-pin to 16-pin adapter for the DLC. There are OBD-1/OBD-2 scanners, but they can be problematic, particularly the Innova brand that has the incorrect database for the LT1 engine, and produces a list of 8 bogus codes.

If you can't find the DLC adapter, uses Shoebox's jumper wire method:

http://shbox.com/1/xraycable.jpg

What are the actual numerical results for the fuel pressure..... "good" is subjective?

Is the Opti new? What brand is it?

The bigger the cam the harder it will be to start. Again, what are the cam specs? "Stage 4" has no standard definition.

1995Cam

fuel pressure is around 41lbs
OPI is brand new, MSD
Cam is .510 "226/234 112 LC

1995Cam

here is exactly what mine is doing! same thing.

timnfxr

What is the fuel pressure normal when the engine dies? Is it still in the normal range?

1995Cam

around 8lbs, like the fuel shut off to the injector. my security light stays blinking the whole time. i didn't think that could be the cause because it starts for a second if it was the VATS its wouldn't start at all.

timnfxr

Yes, the TDM will shutdown the "Fuel Enable" signal if all the security parameters are not met. That's why the Security indicator is flashing. Try cleaning the pellet on the ignition key. I've had it happen to me once after some wrenching, I must have touched the pellet with my greasy hands.

1995Cam

I tried that, going to try and bypass VATS tonight,
if that don't work Im down to my last straw with it.

Injuneer

You say the MAF sensor is "attached". Do you mean plugged in, or actually installed on the rubber elbow so it can measure air flow? Hard to tell from the video.

1995Cam

yes it hooked up to throttle body.

GaryDoug

Normally that would be true, but not if someone has bypassed the TDM line to the starter. The injector control is another matter. Without the TDM signal to the PCM, the PCM will operate the injectors for a few seconds and then shut them off.

1995Cam

i've tried by-passing the VATS but it didn't work. the thing with this car is it had a aftermarket security system (vapor550HF) that i removed, but it was doing the same thing before i removed. i figured that was the problem, but as my luck goes it wasn't. the starter does work like its suppose to and starts with no problem just right after 2 to 3 seconds it dies. im thinking its something in the ECM, what would be a preferred tuning program i can buy to do the tuning myself. a program that will get rid of the VATS and able to tune everything for the mods i've done? ive heard the TUNERCAT has one for LT1 engine, is it any good?

guys looking for any help on this one?

GaryDoug

Ok now the facts come out. It could be the security system failed, causing the problem. Removing it will not fix it, you have to put the car wiring back to the original configuration. Did you reconnect the white/purple wires that the Vapor 550 installation instructions required to be cut?

You don't have to change the pcm program to get rid of the VATS system. You only have to attach a VATS generator module to the line going from the TDM to the PCM. Baker Electronix sells them for $35. It is not the same as a resistor bypass.
http://www.bakerelectronix.com/products_vats/