97 5.7 runs on 7 cylinders but won't on 8

[Road Trip]

I have a 97 k1500 with 5.7 with maybe 220k on the truck ran fine then sat for about year then wouldn't start throws a p1345 code

Hello again Jrivers0688,

Once you get the engine running on all 8 the next step is to get a scan tool that can show you the CMP <> CKP
(CaM Position to CranK Position) Correlation value and see if you can't adjust the distributor housing clocking to
get that within specification. (0° +/- 2°)

NOTE: Even for us spark engine mechanics, the Vortec dizzy is a bit confusing. Instead of twisting the distributor
in order to set the actual base timing on the SBC (like we did from '55-'95) *now* the ignition base timing is triggered
solely by the crank position sensor (CKP) at the front of the crank near the harmonic balancer.

So twisting the Vortec distributor does NOT alter the ignition timing. All the dizzy does is distribute the sparks
to the correct cylinders via the spinning rotor. Even so, the rotor still needs to be closest to the correct cylinder terminal
when the ignition spark is released, so *this* is why we need the CMP<>CKP 'Cam Retard' to be within the 4°
window specified in the Service Manual.

This primarily is in order to help prevent misfires to adjacent terminals in addition to allowing better misfire self-diagnosis
& also sequential FI functionality. (See attached for the P1345 listings in a Vortec-era FSM.)

I know that this is a lot of ground covered quickly, but just letting you know that
there's known solutions for the issues that you are currently troubleshooting.

Best of luck. Let us know what you uncover.

 

[Jrivers0688]

I got it I had bought a new cap and rotor yesterday because they were cheap and it runs the old cap looks new to me no burn marks or anything I'll post a picture

 

[Jrivers0688]

So it's running on 8 but not for long then supdders and dies I set the distributor on 1 with the engine at TDC but I'm reading about 20+ on the spark advance around 1100 rpm when I go backwards it wont start after a certain point do these distributors jump a tooth that easy also when I tested the coil earlier everything was fine except I wasn't getting any reading from the 12v supply through the iron core

 

[1998_K1500_Sub]

I'm reading about 20+ on the spark advance around 1100 rpm when I go backwards it wont start after a certain point do these distributors jump a tooth that easy

Do you ever read the posts that people write for you?

Evidently not.

The answer you need regarding ign timing has already been given to you.

 

[Jrivers0688]

Do you ever read the posts that people write for you?

Evidently not.

The answer you need regarding ign timing has already been given to you.

Yes I do I was just wondering why I might not getting any chance for the spark advance no matter what way or how far I rotate the distributor or really just the cam sensor and cap it's running alright I just can't get rid of the p1345 code the spark advance is about the same all 1100 rpm regardless of the cam sensor position the cam sensor is new it is a napa one though

Ps you don't have to be a dick

 

[1998_K1500_Sub]

why I might not getting any chance for the spark advance no matter what way or how far I rotate the distributor

The answer has already been given to you, at least twice. Everybody's trying to help you.

Ps you don't have to be a dick

?

 

[east302]

Look for “CMP_Retard” or something similar on your scanner - that’s the reading that you’re adjusting to zero degrees to clear the P1345 and not timing advance.

 

[Jrivers0688]

Look for “CMP_Retard” or something similar on your scanner - that’s the reading that you’re adjusting to zero degrees to clear the P1345 and not timing advance.

OK so I'm looking at the wrong data that makes more sense on why there no change I appreciate all the help I just have a limited time to get this thing running again.

 

[Road Trip]

Yes I do I was just wondering why I might not getting any chance for the spark advance no matter what way or how far I rotate the distributor or really just the cam sensor and cap it's running alright I just can't get rid of the p1345 code the spark advance is about the same all 1100 rpm regardless of the cam sensor position the cam sensor is new it is a napa one though

Ps you don't have to be a dick

Hello again Jrivers0688,

*THIS* is what sets the ignition base timing on your Vortec 350:

You must be registered for see images attach

(credit: Google search "Location Vortec 5.7 CKP sensor LINK)

And here's a video where a GMT400 owner goes through setting his CMP Retard to within specs.
It's all in there:

xc_hide_links_from_guests_guests_error_hide_media

And after watching that video, if you go back to reply #11 and reread
it, it should all come together for you. You have everything you need
to know in order to to fix your P1345, you just have to piece it all
together.

Let us know what you discover.

 

[emarkay]

Same, check on that CMP retard. I went through this code a few months ago.

https://www.gmt400.com/threads/scanner-tool-to-set-the-timing.42183/page-8#post-1320079