I have a 1990 Blazer (350 EFI), while i am driving down the road the motor will just shut off. Sometimes it will start right back up and sometimes it will not do anything (no dash lights, starter does not engage. nothing).I will have headlights and tail lights but that is all. When it does start back up I notice the amp gauge flickering from 11 to 14 amps. I have checked and cleaned both battery cables, I replaced the ignition switch (the electrical one on the top of the stering colume) and I also replaced the alternator but I still have the same problem.

I can start it up and let it sit there and the amp guage will flicker and the truck shuts off.

Any ideas?

 

First off you're looking at Volts, not Amps. That doesn't really matter though as the problem sounds like electrical. Since you're lights are working I would assume that the constant hot side of the fuse panel is still getting juice. It is the switched side of the panel that is having issues.

I would start by checking the connections on the firewall just to the left of the brake booster. There is a large fuse junction there and could be an issue.

Electrical can be a very difficult area to diagnose if you're learning. I would read up on Amps, Volts, Current and all that stuff and get a decent Multi-Meter and go check some connections. There is much more information out there than I can explain and they'll do a much better job at it too. Careful when taking readings and disconnect the negative battery cable when messing around with any positive battery cables.

 

Check all wiring and grounds on the truck. On the firewall, under the truck, etc.
You'll find a problem somewhere.

 

The wire (8 gauge with inline fuse) coming from the solenoid to the firewall feeds the ignition. I found that this wire was run close to the exaust manifold and was heating up causing me to lose the 12 volts feeding my ignition and shuting the truck down. I re routed it away from the exaust manifold and replaced it with a 8 gauge wire with no inline fuse and the truck is fine now. I want to replace it with the inline fused wire but i am having trouble locating one.

 

fusible link should be available at any autoparts store. Use four sizes smaller than the wire you're protecting. So for 8ga get 12ga fusible link.

running the wires from the firewall along the top of the engine then back under the exhaust is a horrible design from GM... I found this one when I was rewiring.



I went a little extreme and wired the whole engine compartment.

 

Check that you hot connection to the battery is not oxidized.

I had a problem where suddenly the car wouldnt start sometimes. Someone suggested I cut the end of the battery connection and expose fresh clean wire and the problem went away

 

I think you're a month too late with this post, Rick