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Discussion Starter · #1 ·
Yesterday, I learned what my TDCO and timing are:

TDCO +2.46
Timing +1.5

I performed the "optic bump" procedure in my truck. I want to set TDCO and timing back to factory specs:

TDCO -0.25 -0.75
Timing + 3.5


What is the recommended procedure? I assume moving the optic sensor back 1mm to drivers' side. Then rotating the injector pump?

What should I have for tdco and timing when I only move optic sensor?

Given the info provided above, which way am I supposed to rotate the Injector pump and approximately how much?
 

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1st off what scan tool are you using to view timing
 

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Discussion Starter · #3 ·
these are the #'s that the mechanic at the dealership pulled up with the tech II. He was really confused. Said timing is way off, but truck has plenty of power.

TDCO and timing shouldn't be effected by the optic bump IIRC.
 

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No bump should not affect it, may make it run like Krap if moved too far. Is your dealer's tech qualified to work on a 6.5, I'm not trying to be a smart *** but it is a valid question.

If you trust the dealers tech to be profficient the procedure in the manual should work for him, unless he doesn't have one, you can also use the procedure in the FAQ which is paraphrased from my 98 manual

Was he in time set mode when reading the timing, and are you sure it was a tech II tool, those numbers look like a Snap-On tools display value, where TDCO is at factory level Snap On tool dispalys the number differently, and timing looks like it needs to be advanced, during time set.

The value he should be reading not in time set depending of operating temp of the engine should be 8.5 to about 12 in both actual and desired windows. I suspect an operator error of the T2 tool if that is what he is using, since truck is running so well, if the truck were truly operating at numbers reported I doubt it would even start. Who did your optic bump, did you scribe mark it before moving the optic sensor?
 

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Discussion Starter · #5 · (Edited)
Not sure what his qualifications are. He was replacing an injector pump in another 6.5 when I talked to him. I assume he know what he's doing.

He plugged in the tech II right in front of me. I don't suspect operator error, unless he made the same error twice. He had plugged it in when he was working on the truck. Then he went out and plugged it in to show me fuel rate and timing.

I don't know what mode it was in when he checked it.

He also showed me that fuel rate was at 6mm at idle and said that it's supposed to be at 9mm (maybe because of bump, pcm reports less fuel than actual at idle?)

I did the bump myself. Yes I scribed it before bumping.

I brought the truck home as the mechanic said he was 99% sure that the pcm is bad. (No sense paying $700 for new pcm when mine is under warranty by Wester's.)

If timing is off, it should be fixed. Truck runs okay. I think that the exhaust drone that I have inside the cabin is quite likely due to incorrect timing.

found the tdc set link in the faq's. It's well described and makes sense to me. Thanks!

However, now I have another question. Say for example, I've set my timing to 3.5. Then I learn the tdc offest and it's not the value that I want. I move the IP again and achieve desire tdc. What happens to my timing at this point? Does it even matter?
 

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It doesn't matter, computer controls timing whern not in time set command, the 3.5 avg is base time set I do that 1st then don't worry about keeping it there after I've set the 3.5 avg, but not much movement required to advance the TDC offset, moving the IP doesn't change TDC offset unless learn via T2 tool commands it or you do the KO/KO with APP to the floor & >170F water temp, maybe I'm not 100% correct in my explanation in FAQ but in 5 PCMs now, experimenting with different reflash tune versions, this is how I've done it successfully

Something isn't quite rite if TDC offset is actually +2.4 you should be setting a code, maybe Westers has some insight for you
 

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No bump should not affect it...
Oh it certainly will. Moving the optic sensor to the pass side (retard) has the same effect as moving the pump towards the driver's side (advance).
Not sure what his qualifications are. He was replacing an injector pump in another 6.5 when I talked to him. I assume he know what he's doing.
You know what happens when you *** U ME don't you?
joispoi said:
He also showed me that fuel rate was at 6mm at idle and said that it's supposed to be at 9mm (maybe because of bump, pcm reports less fuel than actual at idle?)
Bingo, this has been discussed in depth many times but yes, the bump cheats the PCM so you get more fuel than it thinks you are.
joispoi said:
If timing is off, it should be fixed. Truck runs okay. I think that the exhaust drone that I have inside the cabin is quite likely due to incorrect timing.
Did it do it before you did the optic bump?
joispoi said:
Say for example, I've set my timing to 3.5. Then I learn the tdc offest and it's not the value that I want. I move the IP again and achieve desire tdc. What happens to my timing at this point? Does it even matter?
Not really. 3.5deg is base timing for all 6.2/6.5 diesels. It is used to just as a reference to time the pump since there are no timing marks.
If your TDC Offset is +2.4 and Base timing is +1.5 then you should probably advance the pump ~2-3deg and then try relearning TDC Offset and see what that puts you at.
 

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Oh it certainly will. Moving the optic sensor to the pass side (retard) has the same effect as moving the pump towards the driver's side (advance).

What I meant was it should not have any impact on displayed timing not that timing would not advance or retard functionally, bumps are supposed to blind to the PCM if I recall from your earlier explanations of it and why to do it.

I'm not a fan of it myself, as it appears that it's very fussy about setting of it, unless I'm misreading where it appears that more folks have problems with it than benefit from it.
 

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Discussion Starter · #9 ·
yup, there was exhaust drone present before optic bump. Increased after bump.
 
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