Blazer dies while running

[bigbadchev84]

So I have a 72 blazer with a summit universal wiring harness in it. I installed it new 5-6 years ago with no problems until now.

I just did a motor swap it has the same HEI dizzy as the last motor, Alt, etc. while letting it run to check antifreeze and purge the air out of the system it will died. It fires right back up, its not a fuel issue, definately power. When it dies my radio beeps (pioneer) just like it does when I turn the key off. I test drove it about a mile and it died twice while driving, but caught itself and fired right back up without me having to touch the key.

I have all power comming off the starter post, I have a 6ga straight to the battery, the one to the fuse block and the battery as well. All connections are tight and I have wiggled them while running and it wont die, also wiggled wires on the back of the ignition switch. It all started after the motor swap and I am stumped to what is causing this!

 

[badmix]

I would look at that wiring again,,anything get "pinched" during the install?

What about the transmission, something causing it to stall out?

Firing order correct? How does it run when it is running

 

[earnett]

I think I would look at the ignition switch itself. You said you checked the wires. It's not stalling out! It's turning off by itself. The radio is beeping when it does this just like if you turned it off. Replace the ignition switch. You could try wiggling the key while it's running to see if can get it to turn off.

 

[ktmoutfront]

Check the ground wires to the frame and body. Don't just look at them. Remove and clean the ends and the mounting surfaces.

 

[bigbadchev84]

The motor itself runs like a dream, I can reach in first start of the day and it fires right up without hitting the gas or anything. This happened right after the motor swap. I just hate diagnosis by replacement. I have a #4 ground cable from the frame to the block and from the frame to the battery. There are 2 more from the frame to the cab as well.

There is no neutral safety switch installed. I will try the ignition switch next, I think I have 5 or 6 of them out in the shop anyways

 

[72blazerguy]

I had a similar problem in my 71. It would be running fine and then just die. Sometimes no power for a bit and then it would start back up. Turned out to be the ignition switch. The wires on the back of the ignition switch were toasted. Just bypass the key switch with a hot wire and you will know if the switch is the problem.

 

[bp71k5]

Do you have a circuit breaker in there powering the fuse block? Maybe one of them is tripping? Some of the new headlight switches have a built in circuit breaker inside them and will reset itself.

 

[diesel4me]

My guess would be a loose connection at the starter solenoid where the positive cable and the fusible link wires connect together,or the fusible links themselves may be partly fried inside and barely sustaining a connection..

It could be the fuse box itself has corroded or is loose where the two halves bolt together--the thickest red wire powers the ignition switch and most of the interior circuts,so look that one over closely....check that junction block near the brake booster too,make sure the wires going to it and the metal bridge on it is not burnt ..

I had my 72 K5 die while climbing a incline one day in traffic,I was able to start it once,then it stalled again a short distance later--when I hit the key to start it again,the starter tried to engage ,then nothing--no power to anything!..

After a half hour of staring and scratching my head in a nearby parking lot I coasted into,I discovered the problem accidentally..a samaratin offered to give me a jump start,and when I tried starting it with a jump,it still did nothing..

I decided to try twisting the battery cables to make sure they were making good contact,and the positive cable had a clump of tape on it under the battery box--I discovered someone had cut off the original side post end on it,and crudely soldered a post type end and 6" of another cable to it long before I bought it --it was all white corrosion and powder under the tape--maybe 2 strands of copper all green,was allowing it to run,until they finally gave up!...