P1345 code assist. Questions. 1996 GMC K1500

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Road Trip

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@Road Trip

Other than going through what drifter went through, is there a way to know that the gear was installed correctly by the manufacturer?

It’s been a while now, but I think mine had a dimple and an engraved mark that when aligned put the rotor between the cam sensor and the #8 triangle. Not sure if all distributors include those markings or not.

(insert view of me climbing out of the rabbit hole, eyes glazed over from reading endless dizzy discussions. :0)

Greetings east302,

I have 2 answers to your question. The first was when the world was right.
And the second, slightly more involved answer, is what we have in 2024.

In the Beginning - How to verify when the 13 tooth gear on your Vortec distributor is properly phased:

Once upon a time, there was order in the universe.
Distributor gears had dimples. Period.
IF the dimple was on the same side of the distributor shaft as the installed
rotor's 'spark terminal', your 13-tooth gear was properly phased. P1345 codes were avoided/cleared.

Note: Reading around, a GM dizzy specialist wrote the following, which appeals to my sense of balance:

You must be registered for see images attach

(credit: https://www.davessmallbodyheis.com/services/general-motors-distributor-gear-information)

Now if you remember the big ol' HEI rotor, at 3000 rpm (distributor, 6K crank)
I bet that 'firing bar' could create a vibration that a dimple could counterbalance?

If nothing else, this gives me a perfect mnemonic to help me remember that the dimple is paired with the rotor's firing tip.

2024 - How to verify when the non-dimpled 13 tooth gear on your aftermarket dizzy is properly phased:

And when the aftermarket guys muddied up the waters by skipping the dimple, we now have to focus on the roll pin
and it's orientation to the gear teeth above. Check this out:

You must be registered for see images attach

(credit: rotor + hardware photo eBay auction? All the value-added techo-grafitti = yours truly. :0)

Q: How confident am I about this advice?

A: Very. Back in March of '02, there was a guy named Schurkey on the Chevelle forum:
You must be registered for see images attach

You must be registered for see images attach


How cool is that? For every right answer out there, there were at least a dozen wrong answers
covering it up. And this was a confusing subject even before folks started replacing worn out
Vortec distributors with affordable aftermarket jobs (that were mis-clocked at the factory), only
to end up with extra tough to clear P1345 DTCs.

Of course I was trying to find really sharp pics of the roll pin under the valley between 2 teeth,
but all the photos I could find were of low quality? But if you have a dizzy in hand, just compare
it to what Schurkey wrote almost 22 years ago & you should be able to tell at a glance.

That's all I've got to say about that.

Cheers --
 
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Schurkey

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Note: Reading around, a GM dizzy specialist wrote the following, which appeals to my sense of balance:

You must be registered for see images attach

(credit: https://www.davessmallbodyheis.com/services/general-motors-distributor-gear-information)
I know of Dave, he's on various forums as "Ignitionman". He's sharp--but I have a (very) few disagreements with him.

This would be one of them. Balancing a rotor at the top of the distributor by offsetting weight at the bottom makes no sense...especially since the distributor rotor has visibly been molded with extra plastic material on the opposite side as the metal conductor. The distributor rotor is self-balanced.

A: Very. Back in March of '02, there was a guy named Schurkey on the Chevelle forum:
You must be registered for see images attach

You must be registered for see images attach


How cool is that? For every right answer out there, there were at least a dozen wrong answers
covering it up...
... just compare it to what Schurkey wrote almost 22 years ago & you should be able to tell at a glance.
What I find surprisingly frightening is that I had zero memory of authoring that, until I searched for the thread on chevelles.com and read the whole thread.

I'm starting to think I'm Joe Biden. My memory is great...but don't prosecute me, because I'm elderly.
 

Road Trip

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I know of Dave, he's on various forums as "Ignitionman". He's sharp--but I have a (very) few disagreements with him.

This would be one of them. Balancing a rotor at the top of the distributor by offsetting weight at the bottom makes no sense...especially since the distributor rotor has visibly been molded with extra plastic material on the opposite side as the metal conductor. The distributor rotor is self-balanced.

Yeah, I also was having a bit of trouble reconciling the counterbalance vs distance thing too. That's why
I wrote the mnemonic comment -- even if his theory wasn't quite right it will still help me to remember
that rotor tip & divot should be in the same vertical plane. (But in my defense an overachiever by
the name of Eaton has persuaded me that there are more things to balance in an engine than I
have been raised to believe.** :0)


What I find surprisingly frightening is that I had zero memory of authoring that, until I searched for the thread on chevelles.com and read the whole thread.

I'm starting to think I'm Joe Biden. My memory is great...but don't prosecute me, because I'm elderly.

Dude, in a previous life I fixed a lot of civilian computer server installations and military
fighter Avionics packages. But people used to be surprised when I couldn't remember
a specific fix on a specific aircraft until we went back into the database and looked up
the history. I used to tell them, "Remember the old adage about not being able to see
the forest for the trees?" I would then say, "I've seen so much forest that I don't
remember any of the normal-looking trees." :)

In other words, if we went out to the jet, the MFLs (Maintenance Fault List) identified
the failing part, we swapped in a new part from Logistics, and it fixed the jet, then
literally no new learning occurred, nothing new to remember = it never made it to my
mental Rolodex for future reference. Then again, the really difficult problems where
we'd reach the end of all possible fault trees & the old gray gal persisted in her hangar
queen lifestyle? I still remember each and every one of those troubleshooting adventures.

...but I digress. What I'm trying to say is that given the sum total of how much you
have 'troubleshot in public' over the years, I think your inability to remember a single
instance ~22 years ago is not necessarily a bad thing. I mean, who wants to be
accused of being a savant? Or that you are one of the 62 people in the world who
have been identified as a Hyperthymesiac? (Hyperthymesia Wiki)

Final thought. Last night I watched our Commander In Chief's speech. I wouldn't
let him pop the hood on the chore truck to change the air filter. Sad but true.

Trust me, you are no Brandon.

And you can take that to the bank.

:waytogo:
 

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shaneroze

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I've had my fair share of distributor fun ngl. On 0°, it will run average ofc, but I set it a tooth behind and have it set close to #1 the ******* runs like a crackhead on bud ice even though it's out of time
 

Schurkey

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Dicking with the distributor DOES NOT change the ignition timing.

It changes the synchronization between the cam sensor and the crank sensor. This keeps the arc from the rotor tip to the plug wire terminal in the distributor cap to a minimum, and allows the computer to correctly identify which cylinder is firing.
 
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Hey all. I have a 1996 GMC K1500 5.7V8 Vortec Engine. I am getting the P1345 code. I have watched many videos and read many documents on this code. I did have a few questions I was hoping to get answered here.

I understand that you can resolve this code with a scanner that will read CMP Retard, which I do not have. Cant I also resolve this issue with a timing light?

I keep reading that you want the timing to be within +-2 degrees of 0. Is this right? I do have the manual but I cant find this spec in there. I may just not be looking in the correct area. Is this +- 2 Degree at idle or 1100 RPM or 1500 RPM? I have read conflicting statements on this.

I recently bought a cheap ODBII scanner. It provides a reading for: "Timing Advance for #1 cylinder" which is coming back at -24.0 degrees. Does Timing Advance for #1 cylinder also mean CMP Retard? If these are two different items/readings, can I use this reading to set my timing?

My plan this weekend is to buy a timing light. Set my engine at TDC for #1 cylinder. Check the distributor rotor to ensure its pointing at the number 1 cylinder in the distributor cap. Loosen the distributor hold down bracket/bolt. Use timing light while turning distributor to try and get timing to as close to zero as possible. I also bought a new camshaft and crankshaft postion sensor. So all else fails I will replace those items.

Does this sound correct in as far as the recommended troubleshooting steps? Am I missing anything? Any other recommendations? Thank you in advance for any information.
Good luck, I just got done fighting this issue and it turned into a big headache!
I finally think Ive got it figured out, these blogs helped immensely! Great community. Any tips or information I know feel free to ask! I am going to finish up ******* with mine this weekend as well.
 

SUBURBAN5

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I got my own little headache. Open to any ideas anybody has. I can not get my cam offset to read +~-2. Best I can do is +~-7. Motor is a ht383e, ac delco distributor. New cam sensor, crank sensor, wires, cap and rotor...
Any ideas where to check? Motor about a year and a half old..
 

Schurkey

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I can not get my cam offset to read +~-2. Best I can do is +~-7.
Any ideas where to check? Motor about a year and a half old..
Distributor won't turn far enough to get it correct? Pull distributor, either turn the gear 180 degrees on the shaft, or merely move the gear one tooth over and reinstall distributor.

My 7.4L seemed to run OK with the offset -29 degrees. But I corrected it "just because".
 

SUBURBAN5

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Distributor won't turn far enough to get it correct? Pull distributor, either turn the gear 180 degrees on the shaft, or merely move the gear one tooth over and reinstall distributor.

My 7.4L seemed to run OK with the offset -29 degrees. But I corrected it "just because".
That's the issue. TDC no problem. Rotor pointing at 1 no problem. But when adjusted its hitting the plenum -7, if I slide it the opposite direction 1 tooth, it reads +7 and has to be maxed out the other way, against the plenum.
 

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