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86 K5 New wiring harness, hard starting issue (Cold or Hot)

Blue87K5

Blue87K5

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Bossier City, LA
I just completed a full wiring harness replacement. Before the swap the truck would fire up like a champ cold or hot. Now after wiring harness replacement I need to crank the truck 10+ times to get it to fire up (cold or hot). My specs are:

Edelbrock 1406 electric choke, ZZ4 350, Edelbrock manual fuel pump, HEI distributer, Keepitclean 85 K5 wiring harness

The only thing I did different is I disconnected the oil pressure switch. I connected the Oil pressure gauge to the oil pressure sender. I connected the electric choke wire directly to the choke. The stock harness had the choke wire going to the oil pressure switch and then to the choke (I think that's how it went). Would disconnecting the oil pressure switch on a Carb'd 86 K5 cause hard starting issues. I know on 87+ K5s the switch acts as a backup fuel pump relay. My other idea is to remove the manual fuel pump & add an electric 5-6psi pump. This problem is really starting to piss me off. Any help you folks can provide would be great!! Thanks

Donnie
 
I've reset timing, checked ignition voltage, and double checked wiring. I can't find anything that might be causing the starting issues. Any ideas???
 
With a carbed engine the fuel bowl should have plenty of fuel to fire the engine.

I am suspect that maybe during cranking that you dont have voltage to the HEI.

Check the power feed to the HEI and have someone crank the engine while you check the voltage.

If the voltage drops way off or goes away then you have found your gremlin.

Good luck

Snowy
 
Sorry, been away for a little while and i'm finally back home. Went to take the truck for a little trail ride and it won't start at all now. It will just keep cranking and never fire up. Put a meter on the HEI power wire... turn the key to run and I get 12+v, but when I turn the key to start the volts drop to 0. I ran a test wire from the starter solenoid post to the HEI power post (with stock connector disconnected) and tried to start the truck and it attempted to fire right up.

Is it time to replace the ignition switch?? I've never had an ignition switch go bad on me before so not sure if this will fix it or not.
 
The ground above the passenger side headlight was a little loose, got it tightened up, but the Blazer still wouldn't start. Went and picked up a new ignition switch from the local parts store and put it in, and viola... the Blazer starts now... but with the original hard starting issue it had right after the new wiring harness install.

Checked voltage to the coil wire and it has full 12+v in run, but still drops to 0 volts during start. The truck will only start when I just begin to release the key to go from start to run.

I'm starting to wonder if the ignition switch harness, that came pre-wired as part of the new complete wiring harness, may be wired wrong. Everything else in the truck runs/works like a champ. Just a problem with this stupid starting issue.

Anyone have any suggestions??

Thanks for the help so far folks!!
 
I'm pretty tired of troubleshooting this issue now. Tracing wires checking all grounds has not led to any fixes. I think I'm going to install a push button starter to fix my no voltage to the distributer during start issue. Since I have good voltage during the run position of the key, I'll just install the push button starter. This way I'll have full voltage while the motor is trying to start.

Make sense to everyone?? Just trying to double check my sanity. Thanks all

Donnie
 
Sounds like your harness is messed up. Things like stereo and HVAC are supposed to turn off during cranking...IGN definitely is NOT supposed to turn off.

Run straight key switched power to the coil, and be done with it.
 
I'm pretty sure 1 of the 2 ignition switch connectors are wired wrong from the manufacturer. I checked voltage on all ACC power wires and when I turn the key to start, ALL ACC power goes to 0 volts.

So I wired in a push button starter switch... and the truck fires up like a champ!! I ran fused ACC power to the switch and ran a direct wire to the starter. So I turn the key to run and push starter button and VIOLA... we have internal combustion!!

Problem solved... hopefully all this might help someone else with a similar issue. Thanks everyone for all the help!!

Donnie
 
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