98 K1500 motor swap but no start

First time doing an engine swap - simple: put a 5.7 from a '97 (with under 100k miles) into my '98 after my 350k miles motor died... Here's the problem: Upon start up of new motor, I turned ignition to run position to check fuel pressure - all good there. I then unplugged my Coil Wire to crank the motor a few times to build up Oil Pressure - all good there. Plugged the coil back in to start the motor up. Click... Click... Then everything is dead - no dash lights / no headlights... Then, 5 minutes later, power returns (dash lights / headlights). I try to start the motor again and same thing - click, click, then everything is dead. Wait 5 minutes and the power is back... What in the world is going on? Brand New battery with full charge - lead wires to battery in good shape - all grounds that I am aware of are in good shape... Anyone run into this problem? Thanks in advance!

DHud said:

I then unplugged my Coil Wire to crank the motor a few times to build up Oil Pressure - all good there.

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Nope. Don't "unplug" the coil wire--at least not the big one. Disconnect the harness connector for the primary circuit.

"Unplugging" the coil wire drives the secondary voltage sky-high. Really hard on the secondary insulation.

There is NO reason to crank the engine to "build up oil pressure". You're just adding crank cycles. Get the engine ready, and FIRE THE BYTCH UP.

DHud said:

Click... Click... Then everything is dead - no dash lights / no headlights... Then, 5 minutes later, power returns (dash lights / headlights). I try to start the motor again and same thing - click, click, then everything is dead. Wait 5 minutes and the power is back...

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Intermittent connection at the battery? Intermittent connection somewhere else?

"I" would inspect the battery cables first. Both ends. Both cables. And make sure the battery terminals and cable-ends are clean--shiny. Not green 'n' fuzzy, not black. Shiny silver-color.

It sounds like a circuit breaker doing what it's intended to do. Why? I have no idea. I suggest making sure your grounds are all connected, a known gmt400 issue.

Schurkey said:

Nope. Don't "unplug" the coil wire--at least not the big one. Disconnect the harness connector for the primary circuit.

"Unplugging" the coil wire drives the secondary voltage sky-high. Really hard on the secondary insulation.

There is NO reason to crank the engine to "build up oil pressure". You're just adding crank cycles. Get the engine ready, and FIRE THE BYTCH UP.


Intermittent connection at the battery? Intermittent connection somewhere else?

"I" would inspect the battery cables first. Both ends. Both cables. And make sure the battery terminals and cable-ends are clean--shiny. Not green 'n' fuzzy, not black. Shiny silver-color.

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Schurkey: Thanks! I cranked it without firing to make sure the bearings were lubed before load is put on them… but even now, after plugging everything in, the same result is happening. It won’t even try to fire the motor - just a click, click, dead… back to life 5 mins later… Did I fry something when I unplugged the wire that goes from the distributor to the ignition coil to crack the motor?

If replacement engine was dry , yes it is a good idea to crank and lube engine especially if you don't know how long engine has been sitting . Sounds like starter circuit , never had this problem on 96 up truck , rechecked grounds and power wires tightness is good place to start . But if you can look at service information from sticky thread above, it will be under service manuals , look in fuel and emissions manual for driveability symptoms and also electrical manual . Hope this helps

docstoy said:

If replacement engine was dry , yes it is a good idea to crank and lube engine especially if you don't know how long engine has been sitting . Sounds like starter circuit , never had this problem on 96 up truck , rechecked grounds and power wires tightness is good place to start . But if you can look at service information from sticky thread above, it will be under service manuals , look in fuel and emissions manual for driveability symptoms and also electrical manual . Hope this helps

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Donor motor had been sitting for over 6 months...and dead motor blew bearings because it got low on oil and my son didn't realize it, so didn't want that to happen all over again! I'm going to check all grounds and leads today just to make sure they are clean. They are tight, but maybe there is some corrosion that I missed.
Not sure what you mean by "sticky thread" - I'm new to the forum thing... Thanks!

Sticky threads are above thread that you are posting on now it will be titled service manuals, I think that's correct , and another thought make sure the stud at starter solenoid is also tight (no movement) and the positive cables at battery that have the spacer in between them . Hope it helps

CumminsFever said:

It sounds like a circuit breaker doing what it's intended to do. Why? I have no idea. I suggest making sure your grounds are all connected, a known gmt400 issue.

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I just went through all the grounds and leads and everything is clean as a whistle and tight as a drum. Still same problem. What sort of Circuit Breakers are there in the truck? Are there some built into the system somehow that I could narrow down the trouble spot? Thanks for your help!

DHud said:

Click... Click... Then everything is dead - no dash lights / no headlights... Then, 5 minutes later, power returns (dash lights / headlights). I try to start the motor again and same thing - click, click, then everything is dead. Wait 5 minutes and the power is back... What in the world is going on?

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This is not a "circuit breaker" except in the figurative sense.

The car is losing all electrical power. Start at the battery, go to the cables--BOTH CABLES, "ALL" THE ENDS--at the battery, and the "other" end--wherever they go. Consider voltage-drop testing of each cable, at each end. Somewhere there's a loose or corroded connection that goes intermittent under heavy load.

I my morning sleep-infused fog, I missed the part where the entire truck goes dead. There are circuit breakers in the fuse box of my '94, metal thingys that go in the same slot as a fuse.
Is it possible that a failed ignition switch could do this?