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No crank no start issue?

Tiny
JR47
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 203,466 MILES
It's my brother in-law truck and the problem was intermittent at first but now it does nothing, he's already thrown a bunch of parts at it which include a starter that does work an ignition switch, park neutral switch, fuse box and a couple fuses and a relay or two along with a fuel pump and filter. I cleaned all the grounds and battery connections and could not find any broken wires anywhere and the battery is working properly. I do know the fuse box had been replaced before and it was from a 04 Tahoe. What I have found is that it will start only if you jump pins 87 and 30 on the starter relay and that the 10amp crank fuse has no power on either side of the fuse if that helps information wise.
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Saturday, June 3rd, 2023 AT 3:52 PM

12 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,320 POSTS
Hi,

The crank fuse receives power only when the key is in the start position. It comes from the ignition A fuse (40 amp), through the ignition switch (start position), and then to the crank fuse. That power actuates the PCM crank signal which should power either pin 85 or 86 of the starter relay. After that, the PCM provides a ground path to either pin 85 or 86 (the opposite one for power) actuating the relay and powering the starter motor.

So, I need to know if the crank fuse was checked for power with the key in the start position. If it was and there was no power, the ignition switch is my first suspect even though it was replaced. I say that because the ignition A fuse also powers the relay secondary side which you said engages the starter when you jump it.

I attached the wiring schematic below so that you have a reference.

Let me know about the crank fuse.

Take care,

Joe

See pics below. Note: I had to cut the pic in half to make it readable for you. I did overlap them so you can follow from one to the next.
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Saturday, June 3rd, 2023 AT 11:19 PM
Tiny
JR47
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  • 99 POSTS
The crank fuse is receiving power, I forgot that the key had to be in start position, sorry.
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Sunday, June 4th, 2023 AT 4:34 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,320 POSTS
Hi,

No problem whatsoever. If that is getting power to the relay, then we need to check for a ground path. Were you able to check that as well?

Let me know.

Joe
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Sunday, June 4th, 2023 AT 9:59 PM
Tiny
JR47
  • MEMBER
  • 99 POSTS
How do I go about that again?
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Friday, June 9th, 2023 AT 6:49 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,320 POSTS
Hi,

To check for a ground path, take a test light and connect the alligator clip to the battery-positive terminal. Then, probe the ground pin where the relay normally is positioned (primary side/opposite of the power supply). Have a helper turn the key to the start position and the test lamp should turn on.

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Let me know what you find.

Take care,

Joe
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Saturday, June 10th, 2023 AT 7:49 PM
Tiny
JR47
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  • 99 POSTS
Is that where pin 86 on the relay would be right? If so, the test lamp isn't coming on when turning the key.
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Sunday, June 11th, 2023 AT 2:59 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,320 POSTS
Hi,

Pins 85 and 86 are the primary side. Unfortunately, manufacturers don't follow a specific protocol, so either of the pins could be power. So, to answer your question, check both to see if power is present.

Let me know.

Joe
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Sunday, June 11th, 2023 AT 5:14 PM
Tiny
JR47
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  • 99 POSTS
The only one I'm not getting anything with is where the 86 pin is when checking for ground path and everything else has power.
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Sunday, June 11th, 2023 AT 6:34 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

When you check pin 86 for a ground, do you have the test light alligator clip connected to the battery-positive terminal?

Joe
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Sunday, June 11th, 2023 AT 7:08 PM
Tiny
JR47
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Yes I do.
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Sunday, June 11th, 2023 AT 7:35 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Does the light turn on? If it doesn't, that is the problem. Let me know.

Also, if that is the case, we need to check the yellow wire at the PCM to see if there is a ground path. If there isn't right at the PCM, suspect the PCM has failed.

Let me know.

Joe
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Monday, June 12th, 2023 AT 8:46 PM
Tiny
JR47
  • MEMBER
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It didn't turn on and I'll let you know what happens when I get to checking the yellow wire.
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Tuesday, June 13th, 2023 AT 2:04 AM

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