[TheDoug]

Hey all my 89 Sierra wont start. I left my lights on for a few hours by accident. I tried to key start it and the starter turned over maybe 3 times before fizzling out. As this happened both indicators began flashing for a few minutes as if I had put my hazards on (although I believe my model does not have a hazard light feature), then a red light down by the ignition began blinking and has continued to blink for a few hours now. The headlights and electronics are still working which means the battery isn't completely drained. I have tried jump starting it with no luck, I cannot even get a spark when touching leads to the battery and the starter motor reuses to turn over. I have also tried clutch starting it down a hill several times with no luck. All my fuses are okay and I have plenty of fuel. Can anyone help me to figure out whats going on? Thanks in advance.

[Gwagensteve]

Sounds like you have some sort of horrible 80’s immobiliser/alarm thing.

[Eddy]

Gwagensteve wrote:

Sounds like you have some sort of horrible 80’s immobiliser/alarm thing.

I'll second that motion.
Exactly what my Vit was doing a while back.
Look around under the dash for a black box type thing.

[TheDoug]

Gwagensteve wrote:

Sounds like you have some sort of horrible 80’s immobiliser/alarm thing.

Eddy wrote:

Gwagensteve wrote:

Sounds like you have some sort of horrible 80’s immobiliser/alarm thing.

I'll second that motion.
Exactly what my Vit was doing a while back.
Look around under the dash for a black box type thing.

Yeah I think you are both correct. I will have a look into it tonight.
Do you have any idea what would have triggered it?
Also I've done a little research on immobilizers and it seems most of them require some variety of hand held button to disable them. I never received such a device when I bought this car. Do you think the previous owner possibly forgot to give it to me? Or will I find some kind of manual way to disable it? (such as a switch or key lock, without having to tear it apart).
Either way I suppose I will eventually remove the immobilizer altogether and re-wire it back to its original state.

[bumstein]

Remove it. Job done.

If you want an immobiliser then rig up an isolation switch, a fuel cut off or pop a new one in.

[TheDoug]

Solved for now. Disconnecting and reconnecting the battery reset the immobilizer, and I was able to get the Sierra started. I'll remove it properly this weekend once I figure out what the 50 wires connecting to it actually do