99 Blazer, "W" 4.3 engine, 2 door, 2wd, auto.

Buying this Blazer from my Uncle. He had it towed to my place to store for a while. It ran and drove when it arrived at my place, I parked it and covered it with a tarp. It sat for 4-6 months I guess. During this time the battery went completely dead. We finally got it uncovered and were ready to start it up. I put about 5 gallons of supreme fuel in it to help it out since it sat for many months. Put a charger on the battery. The engine fires up and runs for about 2 seconds or so then quietly dies. After it dies, security light flashes a few times but goes out. Although my Uncle believed the issue was with the passlock system, I believe the problem is fuel related since the engine will run on starting fluid.

* "Service Engine Soon" is illuminated
* New fuel filter
* There are not active, or stored fault codes.
* Engine will run on starting fluid
* Fuel pressure test's, Engine off;
- Pump on, test port @ ~63psi
- Pump off, test port @ ~54psi
- 10min leakdown, test port @ ~42psi (performed 3 times in a row, dropped 12psi each time)
- Pump on, dead head after filter @ ~98psi

When the engine does start up and run for a couple seconds, there is never any throttle response when I press down on the accelerator, in fact it dies quicker. At this point, the only thing I am led to believe is the SCFI assy may be faulty. I did a little reading and found that this system can be upgraded to the newer MFI assy. So I went ahead and ordered the MFI assy, I figure it will be a good upgrade whether it fixes the no-run issue or not.

Am I headed in the right direction replacing the SCFI assy? Or should I be checking a few other things first? I actually don't know how to test the SCFI to see if it has failed or not.

All help is greatly appreciated!!

 

If there is a massive air leak between your throttle body and mass air flow sensor this will happen. Or if your tubing from throttle body to air cleaner is disconnected. Mass air flow sensor is in between. I beleive you MAY be able to unplug the mass air flow sensor and run without the tubing connected.

 

Update:

Got the new MFI assy installed, and new AC Delco cap and rotor. No Change, still have the same issue. I also bypassed the fuel pump relay to verify that the pump wasn't shutting off during engine run, no change. I pulled a spark plug to see spark, the color appears more white than it does blue or orange. One thing I didn't think to check is to watch the spark and see if cuts out right when the engine starts to die.

I found out today, my time frame was way off for how long this rig sat. It has been sitting for a little over 1 year and 3 months now. Is it possible that I just have bad fuel?? I mean it did run and drive when I parked it and tarped it up back in December of 2012!

The next easiest thing I am going to try is put some fuel dry additive in the tank, and dump 10 more gallons or so of supreme fuel in the thing and give that a try.

 

Give this a shot:

1. Try to start your truck one time, of course from what has already been stated, that probably won't happen, but it is a part of the relearn

2. Once you've tried to crank it, leave the key in the "On" (some refer to it as "Run") position for 10 minutes. Don't cycle the key back at all just try to start it and when you can't, leave the key in the "On" position. Leave it in that position for 10 minutes. At the end of the 10 minutes the security light should stop blinking and go off.

3. After that turn the key to the "Start" position for 3 seconds. The truck won't start.

4. Return the to "Off" for a second or two and then cycle it in one motion straight to the "Start" position and start your truck.

P.S. We had another new member that changed a butt-load of parts I believe and this worked for them. But, in addition...they used a second key when the first one wouldn't work. So, if you have a second key try the above with both keys.

 

^^^ I agree. Flashing security light is a Passlock problem. The BCM is not recognizing the key you're using, and the BCM interprets it as a theft situation. The BCM commands the PCM to shut off the injectors, not the fuel pump.

 

Thanks for the replies guys. I've done some research on the passlock system as that was what my uncle had originally thought the problem was. The reason why I decided this wasn't the problem is because the security light does not continue to flash after the engine dies. It only flashes for a couple seconds and shuts off and does not light up again until the ignition is switched to the off position. I have tried both keys. It is my understanding that if the security light flashes during normal vehicle operation, or REMAINS flashing after the engine dies, there is a malfunction in the passlock system. This is not happening with my vehicle, it only flashes a few times then shuts off. The keys do not have the built in chip/resistor and they are originals so this system has the resistor or whatever built into the ignition switch/cylinder itself. I've read about bypassing the system but consider this a last resort option. Also we have tried the relearn procedure numerous times to no avail. However I will try it again just for hoots when I go to dump some new fuel in the tank later this week.

 

Got the Blazer running today!! xD So happy!

Long story short, I bypassed the passlock system with a 2.2Kohm resistor and did the relearn procedure 3 times and she fired right up and purred like a kitten!

The security light originally never flashed like it should have to indicate an issue with the passlock system, therefor we were never able to do a relearn of the system. It wasn't until I wired in the resistor to bypass the sensor in the ignition that the security light started flashing to indicate an issue with the passlock system and finally allowing me to do a relearn with the new resistance value. So, this tells me the sensor in ignition cylinder must have been intermittently faulty.

 

You can replace the sensor, but why bother? You have it running now Good job.

 

Having the same issue, only mine is a daily driver (has never sat).

Does anyone know how many different resistor values there are? Like I think VATS has 15 different values. Does anyone have a list for the passlock system? I'm guessing they're not all 2.2 kOhms.