Key on but lack of power

[98_k1500]

I have a 1998 k2500 that i am in the process of building and i am having some electrical issues. The acc. position on the key seems to work properly. When you turn the key to the run position, only the accessories come on. The instrument cluster is dead and the ecm is not seeing any power. Fuses are good. If you jump to the ecm fuse with a hot wire, everything works. Truck runs like a champ. I need some wiring diagrams from the ignition switch to the ecm/instrument cluster so i can determine if my ignition switch is bad or if i have some other issue. Anyone had this issue? Also the oil pressure gauge is on the peg past 80 pounds, engine running or not. Help on either of these issues would be greatly appreciated.

 

[badazzbulldog]

check all your connections I went thru this on a powerstroke I installed for a guy and the main harness plug was together but not making a good connection truck would crank but not run and gauges were acting a little wacky

 

[woody31]

Check all the grounds..and fusable links

 

[98_k1500]

Didn know a 98 had any fusible links. I assume this is controlled by a relay somewhere. I will check the main harness plugs next chance i get. Does anyone have a wiring diagram for the ignition switch and the oil pressure gauge on these trucks?

 

[98_k1500]

I finally got a wiring diagram printed off my buddy's Alldata. Time to test the ignition switch plug and the plug that passes through the firewall. I have a sneaking suspicion that its one of the two.

 

[98_k1500]

All the wiring checked good. the ignition switch itself is not working. Does anyone know what tool is necessary to remove the ignition switch from the aluminum bracket it mounts to? It looks like it's got two TINY inverted torx bolts holding it on that i can't seem to get loose. i have never seen a inverted torx this small before.

 

[98_k1500]

Well, I got the switch off and ordered a new one. I decided to take this one apart just to see what happened to it. Contacts look pretty toasted. I took some pics but for some reason i can't upload them.

 

[K15 Blazer]

I had similar problems recently too.... turns out the main "bus wire" to the ECU hookups on the fire wall (which is about an 8' long 8 gauge wire) split open in one spot... voltage leak!!

new (shorter) bus wire, new battery cables, new; and more, freshly wire-wheeled ground wire contacts... problem %100 fixed.

electricity follows laws of science, but its so easy to be overwhelmed and mislead with so many components. start simple, and trouble shoot.

 

[Scrufdog]

my 97 had the switch go bad awhile back. Crappy contact design inside the switch. I took mine apart too. If you need more wiring diagrams I have the Official 97 GM service manuals(2 volumes), should be the same for a 98.

 

[K15 Blazer]

that would certainly be my next suggestion as well... since it requires more work, like, removing the steering wheel... and the air-bag... DISCONNECT THE BATTERY AND TOUCH THE BATTERY CABLES TOGETHER, before touching the air-bag...
what this does is discharge the emergency-deployment-capacitors, which, are designed to deploy the air-bag during a lost of power in an extreme accident... so be safe. don't die.