i have a 1999 blazer in the past three months i have started experiencing the crank but no start issue i have seen alot of info on the forum about this iss, but most revolve around the passlock which is what i thought i was having when it first happened, although my security light has never stayed on other than the normal start up lights on dash then go out but the fuel is disabled. A year ago i replaced the heater core it totally blew on way to work, while tearing out dash i removed bcm at the time i thought it had something to do with hvac bcause where it was located just recently found it to be the bcm. it was full of coolant cleaned out and reinstalled after putting eveything back together and testing tne heater ac controls with no issues i figuer it was ok remember at the time i thought it was assoc with hvac, now a year later im starting to have issues related (or maybe not related) to the bcm. when probs first started was having probs with abs activate at less than 10 mph (about 6 months ago), then the no start issue. I cleaned the abs sensors doing what the tbs said to do for "salt belt states" but no fix ended up pulling fuse to disable abs, prob went away but have no abs now. at least i can stop. i checked fuses related to fuel, bcm, ign, all seem to be ok unless there is one that i missed (checked ones that were labeled as a direct fuse for what i was looking for). i have looked at other threads related but most seem to revolve around passlock issues. am thinking has something to do with bcm but not sure dont understand why am having issues all of a sudden would think if i didnt get something hooked up right when replace heater core figured would notice probs right off?? i have no check engine light when do obd scan only codes that come up are for the abs sys which is disabled i hate wiring pain in a$$ but am really getting tired of getting stranded at work its like a bad dream come true could use help to know if im headed in right direction (bad bcm) or not going to take dash apart to check all wiring connections (process of elimination). apologize for such long post just trying to be as clear as poss with what is doing and what ive done thanks to all. IT FRIDAY BABY!!!!!!!!!!

 

I share your pain. Identical issues on my 1999 Blazer (in Illinois). I have a wire to the bottom of the BCM (black all by itself on the bottom) that isn't connected to anything. I bought this truck a couple of years ago and didn't drive it much but now I want to and have your same issues. If you have a chance could you please follow the black wire and let me know where it goes? Hopefully we can sort out our issues together.

I do know that it wasn't either of the fuel pump or the starter as both have been replaced on my truck in last 2 months. Mechanic obviously can't figure it out either. I am leaning towards ignition switch (lots of info on the Net about this) but need to get that wire back on it's proper place first.

 

You may have two different issues going on. The occasional crank no start would lead me to first do the fuel leakdown test if I was you. It is a common problem on this forum and there are probably a couple hundred posts where the experts state to do this first. The fact that you have no DTC codes would most definitely lead me to do this test before I did anything else. Fuel delivery issues will not throw a code. There are many posts that describe how to do this, but the basics are to get a fuel pressure test gauge from your local parts store (they loan them out). Key ON, engine OFF. The first two seconds when your fuel pump is running you must get a reading of 60-66-psi. Then the pressure must stay above 55 psi for at least 10 minutes. Post your results and folks can help you from there. This is very, very common on Blazers.

 

Ignition switch.

 

I forgot to mention what I thought the second issue might be...I agree with Diata. Diata, instead of two issues could the ignition switch be the whole issue and it's not a fuel delivery issue also? Would it crank with a no start due to the switch?

 

upon further research i believe the problem is an oil pressure issue in that if oil pressure is below i think 5 psi the pcm will send a message to the fuel pump to NOT engage, this is a saftey issue to keep you from smoking the motor. Now why this happens is still not clear if its even the problem, but i do think this is what is happening. Now there is a part that is located in back of engine compartment on the (if your looking at engine the left bank) its an inexpensive part just looks like its a pain to get to. As far as wire hanging on your bcm if that was part of prob i think that you would have issue all the time, although ghost wires are a pain in never knowing what previous owner was thinking or had in mind. I do not have my blazer anymore i had three friggin deer run out in front of me on my way to work and they just killed it, but i have done alot of looking into on this subject and would be more than happy to help you in any way possible. Good luck and i do understand your frustration

 

ETWildPlay the part i was describing is the Fuel Pump Oil Pressure Switch this is different from the oil pressure sending unit. This part is linked from the ecm and the fuel pump and sending unit which then relays to the fuel pump relay control this is why i was targeting this switch my thinking was that if it was sending a false reading this would cause the fuel pump to not engage thinking that you dont have any oil pressure and wont allow you to start because of previous mentioned safety issue i hope this helps and i believe the part is 14-15 bucks from autozone sorry i didnt mention it in last post but wasnt sure what part was called and didnt want to give misleading info. again GOOD LUCK