I have a 92 full size 4x4 blazer with a 350. Every once in awhile it does not want to start. it acts like the battery is dead but all lights work and volt meter shows about 10-12volts. I tested the old starter and it was bad. So i replaced it and it helped a little. it will go days and not have a problem But i will take it into town and When i come out from the store(about 30 mins later) And it will not start. But i let it sit for about 10 mins after trying to start it, It will start right up like nothing ever happened. Any ideas as to the reason for this would be really helpful.... Thanks

 

I think ignition switch. I think while driving it's getting hot.Then cools down and works.Any of your guages acting up while driving ?

 

All the gauges work as normal, except for my oil preasure gauge but i know that the oil preasure sender is junk. i just not had time to swap it out. I think i have it narrowed down to the starter just needs shimmed out. But i cant seem to find a parts store around here that has shims that will work with my truck.

 

And it does not always happen when the truck is hot. It will not want to start after sitting over night as well. But again if i try to start it and it wont, I just wait about 5-10 mins and it starts right up...

 

using any special starter relay other then default? sometimes my old truck would do the same when the cables were taking down the power to much, the starter relay wouldnt engage =(

 

I had a '80 GM Sierra Grande with a 350 & HEI ignition & it had the same problem but after cranking for awhile & then it fired & BOOM went the exhaust. Never did find the muffler or tail pipe lol.
It was the HEI coil that was fubar.

 

Intermittent electrical problems are always difficult to sort out. The very first thing you have to do is to see what's happening with the electrical system when the issue occurs. You need to check the voltage at the battery while trying to start. If the voltage is dropping below 10 volts during the start your battery is the problem. It's unusual but not impossible for a battery to have intermittent problems like this.

Next, check the voltage at the battery and at the starter simultaneously while starting. (And the issue is occurring of course.) If the voltage at the battery is much higher than at the starter you have a wiring problem. Corroded wire or a bad connection.

My guess is that it's one of these two issues. Could also be an ignition switch, but I'd rule out battery and wiring first.

 

Thanks everyone for the help, But after doing nak's idea i found out the battery was junk. It would show 12.75 volts or so but when i put my amperage meter on it and cranked the truck it was only putting out about 400 amps. so i went and bought a optima red top and it has not had any issues since.