98 K1500 motor swap but no start

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

DHud

Newbie
Joined
Jun 10, 2024
Messages
40
Reaction score
67
Location
Wisconsin
No problem, I enjoy helping those willing to learn. To answer your question, if you were to flip your Underhood
Fuse block upside down, the part that connects the battery cable input to the fuses is referred to as the power bus.

What you are really looking for is something that you can easily touch with your voltmeter probe, so the "Aux A" and
Aux "B" connectors at the back are perfect for this IF the fuses feeding those are installed. I've modified the Bird's Eye
view of the fuse block to make this a little more clear:

You must be registered for see images attach



Fun fact - if you go back to the last wiring diagram, these 2 outboard power connections are referred to as 'Stud A' and 'Stud B'.

Notice that since my chore truck ('99 C2500) didn't come with any options (police, camper, etc) that would make use of these
outboard power studs , they didn't bother to populate those 2 fuse locations. However, on your vehicle if the fuses are in place then
just touch your voltmeter to one of these studs. If your truck is like mine, then while the truck is working correctly try and
probe where the circles are and 2 out of the 4 locations should reward you with a quick place to check the voltage in your
Underhood fuse block.

The idea is to find a place where you can easily compare the power in your fuse block (that feeds the entire vehicle) vs the
power right at your battery terminals. And all we're trying to do is figure out what's going on when everything goes out on
your truck right after attempting to crank the engine over.

Hope this cleared up any confusion. Happy hunting --
Very helpful! Thank you!
 

DHud

Newbie
Joined
Jun 10, 2024
Messages
40
Reaction score
67
Location
Wisconsin
Just did the Voltage check - and the +12v power bus in the Underhood Fuse Block is the same as the battery voltage after failure… and battery is reading as expected. Per your previous post, next step is to pull starter and bench test it?
 

DHud

Newbie
Joined
Jun 10, 2024
Messages
40
Reaction score
67
Location
Wisconsin
Update: since the last “fail test” earlier today, the power is not returning as in all previous times. Truck is still without power over an hour later. It was taking 3-5 mins to restore all other times, but now it’s dead as a doornail!
 

Road Trip

Supporting Member
Supporting Member
Joined
Jul 8, 2023
Messages
1,427
Reaction score
4,072
Location
Syracuse, NY
Just did the Voltage check - and the +12v power bus in the Underhood Fuse Block is the same as the battery voltage after failure… and battery is reading as expected. Per your previous post, next step is to pull starter and bench test it?

The short answer is yes, this would be the next troubleshooting step.

* You have duplicated the failure with manual jumpering of the power side of the crank circuit.
* You haven't reported any fuse blowing (thinking 40A IGN A) so this tends to eliminate the
starter solenoid. On the other hand, the actual starter motor has a 2 gauge cable going to it with no
circuit breaker or inline fuse, so if there's an internal failure it can draw a lot of current.

****

Q1: Is there a history of issues with the starter, or has it been a solid performer prior to the engine swap?

Q2: Has the truck changed behavior since what you originally wrote in your original posting? (Reply #1)
Do the truck lights recover immediately after the cranking attempt? Or does it still take several
minutes? (Your reply #34 just came in.) < Based on this, is the battery voltage still ~12.0v-12.6v
across the terminals? And if you check the voltage at the Underhood fuse block that this still
matches the battery?

Please share any/all details about the electrical system. Is EVERYTHING dead, or do certain things
still operate? (Heater/AC fan, radio, any lighting, etc.)

Right now I feel like I'm missing an important clue?
 
Last edited:

Keeper

Supporting Member
Supporting Member
Joined
Dec 6, 2020
Messages
704
Reaction score
1,693
Location
Northern Virginia
When you first cranked it with coil disconnected, did the engine spin freely throughout the cranking cycle, or was it slowing down?

Did you hear/see donor motor run? Was any work done to the donor engine between pulling it and putting it in?
 

Road Trip

Supporting Member
Supporting Member
Joined
Jul 8, 2023
Messages
1,427
Reaction score
4,072
Location
Syracuse, NY
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,

I've been puzzling over your problem description. (I always believe what folks describe, even if I can't explain why they would see this?)

OK, when you tell me that the lights disappear for ~5 minutes, and then return? I *can* explain that, since the headlights do rely upon
a circuit breaker instead of a fuse. It's part of the headlight switch, and here's a quick description from the '99 FSM:


You must be registered for see images attach


My problem is trying to explain why this circuit breaker would be opening immediately after
you attempt to crank the engine over? The only explanation I can come up with is that you
somehow missed replacing the ground strap on the newly swapped motor, and somehow
this missing ground is causing a backfeed through the headlight circuit?

I know this sounds crazy, but when the grounding system is disrupted, all kinds of weird behavior
is possible/has been observed over the years due to backfeeding?

When you get a chance, I'd like you to verify that there aren't any disconnected grounds hiding
behind the firewall and the right rear of the engine. And also the large ground that goes on
the right front of the block. More in a bit.
 
Last edited:

DHud

Newbie
Joined
Jun 10, 2024
Messages
40
Reaction score
67
Location
Wisconsin
A1: No history of issues with Starter - truck started fine every time with old motor - no hesitation. Reinstalled same starter with new motor assuming it would be fine. Starter looks pretty worn, but when taken out, it operated as expected.

A2: The only behavior change since the beginning are 2 things: 1) Upon initial startup process, I could get the motor to crank without ignition. When adding ignition, it did the "ping, dead" thing. The first time this happened, I was able to unplug the ignition and get the motor to crank again, but after plugging the ignition in and trying a second time (getting the same results as the first) I could no longer get the motor to crank even without ignition plugged in. From that point on, no matter ignition or none, the motor will not crank. The only result I get is "Ping, Dead". 2) As of today, the power is not coming back on at all - or at least within the hour that I had at home before leaving. Where it would previously return within 5 minutes, it has not yet returned. Battery terminals and Fuse Bus terminals still read as before - right around 12v. I have not checked AC or Radio or headlights - I just noticed there were no dash lights or sounds... which is a new situation. I can and will doublecheck all of these things (including Ohmmeter check) when I get home again later this afternoon.

Either way, I feel like I need to get a good inspection of the starter - or even just replace it for precautionary purposes...
 

DHud

Newbie
Joined
Jun 10, 2024
Messages
40
Reaction score
67
Location
Wisconsin
When you first cranked it with coil disconnected, did the engine spin freely throughout the cranking cycle, or was it slowing down?

Did you hear/see donor motor run? Was any work done to the donor engine between pulling it and putting it in?
Crank was strong - no issues or fading... And yes, I heard motor run before it was pulled. Motor was stored in dry place for about 6 months before install. All I did was replace Oil Pan and Valve Cover gaskets, new spark plugs/wires, thermostat, and installed new Power Steering Pump and Water Pump. I had the distributor cap removed for install, but not the rotor.
 

docstoy

I'm Awesome
Joined
May 8, 2024
Messages
242
Reaction score
161
Location
Kentucky
Back to a question that hasn't been answered , Can engine be turned by hand and not starter ? Another thought while it's dead have you got voltage to underhood fuse block fuses and relays ? If engine will turn by hand and you have voltage to underhood fuses and relays the next step would be to look at power going from underhood fuse block to ignition and dash fuse block
 
Top