76Ventura

Hi guys. Earlier this year I bought a 1976 Pontiac Ventura that has the wiring harness, engine, and transmission out of a 1995 Chevy Caprice 9C1 (police car). It has the LT1 and 4L80E. I'm having trouble getting it started. Hasn't started since about October of 2016.

Now here's my problem: it's just turning over. If I spray starting fluid into the intake, the car fires for a split second and then dies. I'm brand new to the LT1 engine. Can you give me an idea where the fuel isn't going through? I'm getting fuel through the line, through the fuel pressure regulator. Is it possible that all 8 of my injectors are clogged up, or is it another problem? Thanks in advance for the insight.

aliceempire

iTrader: (14)

Did you put a fuel pressure tester on it? What is the actual pressure?

Street Lethal

iTrader: (16)

Sounds like the injectors aren't firing, or aren't being triggered by the PCM. Did you, or the former owner, disable VATS in the PCM? Which key are you using to crank the engine, the original Ventura's key, or the Caprice key with the little resistance pellet on it...?

76Ventura

Ventura's original key. Everything is hooked up to the car, ran fine for 2 years before October of last year.



I have not yet tested fuel pressure, I don't have a gauge for doing so.

kevins88ss

Street Lethal nailed it, unless he bypassed the VATS key chip, that sounds exactly like the computer not enabling the injectors. Painless makes a VATS bypass module. Runs off 5v dc and bypasses the key resistor.
I did one when I swapped in a 96 3.8L into our 94 Camaro and the 98 computer was expecting a different resistance so it'd turn over all day but not fire.
Two things you'll need:
https://www.summitracing.com/parts/prf-64023


You'll need to know which wire off the computer you'll need to tap into. It may be different than the one I needed to tap for the 3.8L.


Let me know if you have any questions.

kevins88ss

From shbox . com. Excellent site for LT1 info. http://shbox.com/1/pass_key.html

76Ventura

My problem is though, the car ran just fine for 2 years every day before I got it. Previous owner said he started it about once a month after he got his new car, then it would just crank and not fire. Would the VATS kick in for some reason?

kevins88ss

There's only two ways to get an LT1 that's computer controlled to start in a normal manner - either you have the VATS key system in place (from the key, key cylinder, and wiring to the computer) or you bypass it (either by sending out the computer to remove the VATS feature or use something like the Painless bypass module).

Check out the key - does it have a small resistor at the top? If not, then ask the previous owner if they know if it had a bypass installed or the computer was reprogrammed to remove VATS.

Here's a VATS style GM key: https://lock2000.files.wordpress.com/2012/05/vats.jpeg

Have you ever heard it run?


BTW, love the car. I had a 76 Nova Concours hatchback, inline 6 back in the 80's. One of my favorite cars.

Firebat

iTrader: (7)

If the LT1 ran before, 2 years ago, then odds are the vats was already bypassed. If I remember correctly (its been 10 years or so since I bypassed my vats), if Vats isn't disabled then the car will still start up for 1-2 seconds then shut off. Sounds like yours isn't starting at all unless starting fluid is applied.

So, let's assume VATS isn't it and it starts only with starting fluid. Since it does start then that probably eliminates anything air or spark related.
Recommendations:
1) Make sure you have no huge rips in the tubing from the air filter to the engine just in case.
2) Check power going to the fuel injectors and/or check fuse for the injectors. Check all fuses while your at it.
3)Invest in a fuel pressure gauge. If fuel pressure is low then check for leaks, replace fuel filter, replace fuel pump.

kevins88ss

I'm not sure that's accurate. VATS effectively disables the fuel injectors. We need to know if he's heard it run or not.

Understanding GM VATS (PassKey)

This system seems to cause much confusion, stress, and misery. Hopefully, this will help elevate some of that. VATS stands for Vehicle Anti-Theft System. It is commonly referred to as PassKey. Later versions include PassKeyII, PassKeyIII and PassLock (which uses no resistor "pellet"). GM first introduced VATS in 1985 on the Chevrolet Corvette, and after proving successful, was later introduced in other models in later years. Lets break it down even further:

Operation: Operation is fairly simple, but lets discuss what all makes up the PassKey system. The most obvious part is the key. The ignition key as a little "chip" in it. This is a resistor "pellet". There are 15 possible resistances, therefore 15 different types of keys each with a different resistance. This reduces the likelihood of a potential thief from having the correct resistance resistor on hand. Then you have to have a special lock cylinder to "read" the key. I use the term "read" loosely, because it does anything but read the key. I will explain more later. Next is the VATS module. It does most of the security work. It is the "brains" of the system. The module is what actually "reads" the resistance, but has to do it via the contacts in the lock cylinder and the related wiring. Think of the module as a Multimeter, and the wires and contacts the Multimeter Leads. The module reads the resistance and determines if the resistance is the correct value. The module will go into several modes, depending on what the module sees. There is "Tamper" "Normal" and "Fail Enable".

Normal: Normal is when the correct resistance is seen during cranking and the module will ground the Start enable relay, and send a "Fuel Enable" signal to the ECM. This basically "turns on" the injectors. If the Fuel Enable signal is lost or not sent, the injectors will never pulse. The signal is a unique "Pulse Width Modulated" signal, which is a series of rapidly switched "on" and "off" voltages. Once the relay is grounded, voltage is allowed to the "S" terminal of the starter, and the ECM is told to pulse the injectors and the car starts.

Tamper: This mode happens when the vehicle is cranked, and the resistance value as seen by the module is not the same as the value stored in the module. When this happens, the module shuts down for 4 minutes. Even if the correct resistance is then seen, the car will not start for the 4 minute "time-out". Each attempt to start the car within the 4 minute "lock out" period, will reset the timer. The security light will also illuminate for the 4 minutes. The Start Enable Relay will not energize and the Fuel Enable signal will not be sent. HINT: if the key pellet is dirty, it will put the module in the "Tamper" mode. If your car fails to crank/start and the security light comes on, try cleaning the pellet, wait 4 minutes, and try again.

Fail Enable: This mode is to help keep the motorist with the right key from being stranded. If a failure happens to the PassKey system AFTER a valid start, this mode is initiated. It allows the vehicle to be restarted, even with a failure present. The security light will remain illuminated to let you know a failure is present. However, this also means that the car can be started w/o a key, and is vulnerable to potential thieves. If battery power is lost while in fail enable mode, this mode will be lost and the next attempted start w/ the system malfunctioning will cause Tamper Mode.

76Ventura

Well, folks, turns out that the injectors weren't firing. I had a friend who has some experience with LT1s check it out; replaced two $6 relays and she fired straight up. I've had no problems cruising her around and hot rodding. Thanks for everyone's help.

kevins88ss

Nice! Good job and thanks for the follow up. You never know when it'll help the next guy.