It is not my vehicle, it is a friends that is not too savy with fourms, so I am posting on his behalf. It has the 4.3 liter motor and the spider injection was replaced last year.

It will not start on its own, meaning if you spray starting fluid in the throttle body it will fire up and run, never missing a beat and drive around all over town no with no problems. If you just try to start it normally it will never hit. Even if you try to start it right after you shut it off from it running for 30+ minutes around town.

I hear the fuel pump, and obviously it is working because it runs for longer than 30 minutes.

Now he has said that on cold mornings( around 20 degrees F or colder) it will not start, even with the lighter fluid. After it gets a little warmer it will start.

I checked the MIL By jumping pin A and B together and it flashed code 12. (if I am reading it correctly) From what I have read that means no error.

I apologize in advance if this is in the wrong section and thank you guys in advance for the help or suggestons

 

had the same problem, it's the fuel pump, when your trying to start it, you only have about 10 volts and thats not enough for a weak fuel pump to create enough pressure to open those poppet valves. but as soon as you let go of the key and the starter disengages, you have 12.5+ volts, just enough for the fuel pump to do it's job, replace it now or risk bending a rod and have to rebuild the engine like i did. starter fluid it very hard on an engine.

 

I would not guess the fuel pump already
I suggest you run some tests to the fuel system 1st before diagnosing its the pump

follow this
96+ Fuel System Diagnosis - Blazer Forum - Chevy Blazer Forums

it works for all cpi engines

 

2x on danger of using starting fluid in a gas engine.

The voltage drop makes good sense.

 

Having the same issue with my '93 s-10 blazer. It's pretty cold out here right now (20 at night, 40 in the day). For a couple weeks, I have been cycling the key back and forth a couple times to build pressure from the fuel pump and it would start. A few days ago, it just wouldnt start up. It cranks over but wouldn't start. After reading this thread, I hooked up jumpers from my other car and the blazer started right up. I am going to have the battery tested tomorrow, but the battery is only a year old...

 

I would say to check the wires that go to the spider injector they go bad and are very tricky to trouble shoot . Try wiggling the wire then try and start it . I had the same problem to and I changed everything . The spider the pressure regulator , fuel pump , tank , sending unit , and then I found the problem . After I did the spider it ran fine , I went to a friends house and it wouldn't start and thats when I tried wiggling the wires .Hope this helps .

 

I would say check the connections on the battery and make sure you have good fuel pressure on the check valve on the back of the intake on the driver side. Needs at least 60lbs. Definatly sounds like a fuel problem