I’m not sure if I put this where it’s supposed to go so I apologize in advance.
So it all started the other day. I was driving and the tacho needle jumped and everything was fine. It happened about every hour of drive time. Well, yesterday I go to start my blazer and no lights except the battery light were on the gauge cluster. Only half of the backlight was lit as well. It would just crank but never fire. I’ve checked fuses already. Anyone have an answer?
It’s a 1998 LS if that’s important

 

Can you hear the fuel pump run for 1-2 secs when key is turned to ON?

 

Yes. The fuel pump cycles as normal. The fuel pump was replaced about 5k miles ago so it “should” be okay

 

The stepper motors used for some the gauges can go bad. I had my speedometer needle get stuck at certain values and then jump. This might or might not be related to what you are seeing, but I thought I'd mention it in case it helps with the diagnosis.

And when you saw the tach jump, there was no corresponding change in engine speed. Right?

 

Seems you have two problems, instrument cluster and engine not starting.
Did you use a Delco fuel pump when it was replaced?
Check the easy stuff first; battery terminals/connections, battery condition, coil wires in place and all good. I assume there is good fuel in the tank, no water, not old fuel.
Then time to check the fuel pressure at the fuel rail port.

Regarding the instrument cluster; could be the connector on the back has come loose, or the frame/ground connection has. Getting to the instrument cluster's connection is not all that difficult, just requires removing trim panels, keeping track of what screws go where. Any aftermarket alarm system installed?

 

Plenty of good gas. It was a Delco pump. I went out to look at it this morning and turned the key and everything was normal and it started right up. A couple seconds later the gauge cluster lost power again and the engine died. Where is the gauge cluster grounded at? I’ve wiggled the connector and nothing changes. Would the gauge cluster communication to the ecm cause it to die when it loses power?

 

That's a weird one. I'm not 100% convinced it's a cluster problem because it should still start and run without a cluster. I'm pretty sure I ran my 99 without the cluster (and a dash in my lap) when I replaced the heater core years ago and I wanted to make sure there weren't any obvious leaks before putting everything back together. I did NOT want to have to take everything back off again. Either way, the cluster is using the common chassis ground through the ECU so you'll have to check all the chassis grounds starting in the engine bay for the 'big' ones. You might want to check the fault codes with a 'good' OBDII scanner. There's a few $20-30 options like the BAFX that's known to work (and works better than my $300 bi-directional scan tool that I bought years ago for reading codes). It helped me find which circuits were open and solved a rather embarrassing mistake I'd made during a previous repair.