changing injector timing

**9365turbo** · 10-29-2007, 20:33

I have a 93 k3500 6.5TD. It has a intercooler,new injectors,home made cold air filter kit and free flowing exhaust. Its MPG is 13 in town and 17 on highway at 70mph. Will messing with the pump timing make better MPG or what? I also turned the pump up a bit.

**Robyn** · 10-30-2007, 08:04

If its running good and starts fine I would not mess with the timing.
The numbers you are showing are about normal for a 1 ton.
Drop the cruising speed down to about 60 and the Hwy numbers will come up some.
My 95 dually will see 18 Hwy and 15 city if I behave myself

Ramping up the timing a tiny bit to compensate for timing chain wear wont hurt but just a little bit.
Too much and the sucker will rattle badly.

Getting a good idea where its at would be a better starting place rather than arbitrarily advancing it.

Since you tweeked the IP some this is going to steal a little MPG however it will give a little more power.

If the IP has a lot of miles on it you could be seeing some power and MPG loss from wear within the pump.
Over time the advance piston wears and this can take its toll on things.

Good luck

Robyn

**jpgreen** · 10-30-2007, 08:44

I want to be able to set my own timming on my trucks.

What gage/tool/scope do I need to buy to accurately set injection timming on a 6.5 electronic and 6.2 DB2, and where do they sell it?

None of the mechanics in my area can set this timing.

**9365turbo** · 10-30-2007, 10:29

I will leave it alone then. I asked because I'ved seen people on here with the timing changed,but they might have had the electronic pump were as I have the mechanical one. My truck does have 180,000 miles on it. the truck does run good and starts good. It probally wouldnt hurt to have the pump rebuilt.That will have to wait until next year.The only thing I have noticed more since putting the intercooler on is the oil from the CDR seeping out of the tubing to the intercooler. Which I seal up with silcone sealer.

**Wing Nut OOA** · 10-02-2010, 15:28

with a 95 you can view your timing specs with the engh motors GMTD ScanTech program

it also has a TDCO set and TDCO learn that you can use in conjunction with manually rotating the pump to get your target Injection Timing.

**Wing Nut OOA** · 10-02-2010, 15:38

IN ADDITION! since i am for some reason not able to create a new thread at this time.

what would you do in the situation where your Desired injection timing and Actual injection timing are 8.5 while the TDCO is 0* and it is adjusted all the way to the passenger side, yet STILL 1/8 inch off the timing mark. the slots in the pump wont let it rotate any further.

i hear people running up to -1.75 for towing purposes (is that right?) and -0.5* is stock but mine is stuck at 0.

i can rotate it the other way and it was at +2.02 but i dont think that is where it should be run.

i've heard people say anywhere between + and - 2.02 is fine yet i'm throwing a code 88, and just started with a code 56.

**suburbanK-2500HD** · 10-03-2010, 00:33

The code 88 means that the pump timing is outside the adjustment limits of the Ecm.

Code 56 - injection pump calibration resistor error. The PCM uses a calibrated resistor to determine fuel rates. The resistor value is stored in the PCM memory. if the PCM memory has been disturbed or the PCM has been replaced, the PCM will relearn the resistor value ot the next ignition cycle.

DTC 56 will set when PCM has lost its memory and is unable to read a resistor value on the next ignition cycle. Possible poor performance problem. PCM will default to the MIL will light and, a current hisory DTC 56 will set. PCM will default to the lowest fuel table.

Check connection´s it could be it causes this.

**JohnC** · 10-03-2010, 10:42

Running TDC offset learn causes the PCM to re-read the resistor value as well.The resistor is probably missing, since the last PMD replacement.

If the pump is outside the normal range, the PCM may store 0 as a default. I don't really know, but I'd try going back to center and re-learning TDC offset.

Come to think of it, the resistor error may prevent the relearn from working. Fix that first.

**Wing Nut OOA** · 10-03-2010, 16:06

i cant "re center" and start over.

the timing marks are 1/8 inch apart and its adjusted as close as i can get it.

now i got to thinking that maybe someone replaced the timing chain and got it a tooth off.

then i got to thinking it wouldnt matter if you got it 10 teeth off or just left the timing chain off all together, the slots in the injection pump will in NO WAY let it be rotated far enough to line up these marks.

now as far as the resistor.

where is it and how do i go about changing it.

**Wing Nut OOA** · 10-03-2010, 19:08

i am able to create new threads now so please see mine. apologies for the hijack

EDIT: false alarm......

95 K2500

i've got the pump rotated ALL the way towards the passenger side and the timing marks are STILL 1/8 inch apart. my TDCO is 0 degrees and i would like to see between -0.5 and -1.0 degrees

my desired and actual injection timing both measure about 8.5

i tried turning the pump the other way and that just got me a TDCO of +2.02

what should i do.

**suburbanK-2500HD** · 10-04-2010, 08:34

Have you checked the timing chain.
I did that error my self once, and got all sort of problems setting the timing.
And i was 1 tooth wrong, the truck was running, but poorly..

**JohnC** · 10-04-2010, 08:37

Originally Posted by Wing Nut OOA

i cant "re center" and start over.

the timing marks are 1/8 inch apart and its adjusted as close as i can get it.

Then the marks are wrong. Changing the position of the timing gear relative to the chain won't alter the fact that the timing marks won't line up, so ignore them.

Moving the pump 1/16" makes a huge difference in the TDC offset. If it's +2.02 at one extreme you should be able to get what you need. Fix the resistor error first.

The resistor is inside the connector of the FSD on a tiny circuit board pressed over the pins of the connector. I suspect yours is missing.

**Wing Nut OOA** · 10-04-2010, 15:30

i'm not desperately trying to get the timing marks to line up. i know they wont because it appears that either the timing cover or the pump is different from stock. maybe wrecking yard parts.

the fact that the timing marks arent lining up doesnt bother me really its what i need to do to fix the timing issue.

i will check for the resistor. i have changed the PMD so maybe i messed something up.

so if i unplug it it should be inside the plug pressed over the pins?

EDIT:

If it's +2.02 at one extreme you should be able to get what you need

i maybe wasn't clear on this. i had only moved it about 1/16 to 3/32 to get the +2.02 reading.

the metal fuel lines would in no way let me rotate the pump from extreme to extreme.

**Wing Nut OOA** · 10-04-2010, 16:09

okay so i unplugged the connector from the PMD and used a mirror and flashlight to look up inside there (remote mounted) i saw nothing but about 6 or 8 little prongs. and as far as i can tell the other side of the plug doesn't have a way to accomodate a resistor.

am i missing something?

**Wing Nut OOA** · 10-04-2010, 16:14

well lets start with this...

i aint got one.

where do i purchase one of these little gems

EDIT:

just went and bought dorman PN/904-107 for 23.99 at Advance Auto Parts.

be here in two days.

comes with the #5 AND the #9.

**JohnC** · 10-05-2010, 09:27

Put in the #5 and adjust the pump so the solenoid is vertical and redo the TDC offset learn. See what you get. In the end you may have to loosen the fuel lines to make the final adjustment.

There are no "official timing marks" for the pump, so the fact they don't line up is not surprising.

Your old resistor is likely in your old PMD...

**Wing Nut OOA** · 10-06-2010, 17:34

okay i'm callin it quits at -1.58

i got it to -1.94 but it kept bouncing up to -2.02 and i dint like that.

i may mess with it some more at a later date but from what i've read i'm a full degree beyond factory specs so i should be good.

most folks were saying between -0.25 and -0.75

power seems excellent. i dont have to depress the pedal as much to take off and cruise and also if i step on the gas while cruising the boost goes up and i gain speed without downshifting, where as it was prone to doing before.

peak boost seems to be between 8 and 10 which is what i've been seeing as a standard.

tranny temp was just over 100

the only other thing is my EGT. i thought maybe it would come up to normal operating temperature after i fixed my problems.

it still stays between 250 and 300 (guess) while driving.

i know after i get home and grab my infrared thermometer the surface temp of the crosspipe is a little over 250.

got 260 just now.

my EGT gauge doesnt start reading till 400 so i cant even really check to see if it works.

makes me a little worried.

what should i be looking at for operating EGT without towing?

**JohnC** · 10-07-2010, 07:44

Sounds like the EGT gauge is not working. Depending on where your probe is located, you should see 600-800 loafing and 1000-1200 under heavy load (roughly).

**Wing Nut OOA** · 10-07-2010, 18:42

yeah thanks for the #'s.

but i did find out that i was supposed to put it in the passenger side exhaust manifold.

i have it in the cross pipe on the bottom driver side.

my bad dawg...

Thread: changing injector timing

Thread Tools

Display

changing injector timing

Posting Permissions