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What can you guys tell me about Resistors?

Darkrider

Darkrider

Lobo Solitario
Messages
240
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Location
Lloydminster, SK Canada
Ok i ordered a new PMD w/relocation kit from Leroy on the 5th and it is coming with a #9 resistor in it. Now i have a #6 in my current PMD. What i was told by the previous owner of the truck was that i need to have my Resistor matched to the one in the ECM of the truck otherwise i risk burning up the PMD. Is this true? What affects will having the #9 in the PMD have on the truck if any?
 
With obd-1 the ecm will relearn the resistor value within the next 50 key on cycles. Until then it will use the #6 value.

It's nothing to worry about.
 
NVW said:
With obd-1 the ecm will relearn the resistor value within the next 50 key on cycles. Until then it will use the #6 value.

It's nothing to worry about.
Click to expand...

Ok so i can put the PMD in with the #9 and as you said it will relearn basically after 50 starts. What effect will changing Resistors do though?
 
Each higher # adds approx. 1/2 mm3 of fuel. Their purpose was to fine tune each IP so they put out the same mm3 on a flow bench.
 
Ahhhh ok. So really i'm adding a minor increase in fueling with the new resistor. Prob not a noticeable amount but at least its a step in the right direction especially if i decide to add a bigger turbo later on.
 
Darkrider said:
Well my buddy (the po of my truck) was told this by the local gm dealer

Sent from my SGH-T959D using Tapatalk
Click to expand...
Not surprised the dealer was the source, its common for the dealers to BS clueless customers as a matter of keeping them off their back.
This is going to get worse IMNSHO These days so many kids don't have a clue about anything practical. Cars, carpentry, any hands on skill. They have no framework from which to call BS from. Ok I am shutting up now and going to bed. :hihi:
 
L98TPI said:
Not surprised the dealer was the source, its common for the dealers to BS clueless customers as a matter of keeping them off their back.
This is going to get worse IMNSHO These days so many kids don't have a clue about anything practical. Cars, carpentry, any hands on skill. They have no framework from which to call BS from. Ok I am shutting up now and going to bed. :hihi:
Click to expand...

The friend I bought the truck from is an old friend of my fathers who taught me a lot of what I know about vehicles in general, However when it comes to the Gm diesels we have long since past the point where I have started to teach him what I have learned from here. In fact I have already printed out pics of the optimizer block to help him id if he has one in his '97 Chevy C3500HD or not. And I plan on eventually printing out all the info I can find in converting from the DS4 ip like my truck has to the mechanical ip, there is a pretty good chance I can snag the DS4 from the HD when that time comes.

Sent from my SGH-T959D using Tapatalk
 
Darkrider said:
The friend I bought the truck from is an old friend of my fathers who taught me a lot of what I know about vehicles in general, However when it comes to the Gm diesels we have long since past the point where I have started to teach him what I have learned from here. In fact I have already printed out pics of the optimizer block to help him id if he has one in his '97 Chevy C3500HD or not. And I plan on eventually printing out all the info I can find in converting from the DS4 ip like my truck has to the mechanical ip, there is a pretty good chance I can snag the DS4 from the HD when that time comes.

Sent from my SGH-T959D using Tapatalk
Click to expand...

search for username bobbiemartin.

he posted a pdf on a complete db2 conversion.
 
Am sure a search will get me results to this question if I want to slog through all the returns (like I got the last time I tried), so am asking in a fresh thread, and here goes . . .

Physically / mechanically, what does the #9 (or any) resistor do? I got it that the effect is to add fuel, but how? Does it change the voltage going to the IP so the plungers start earlier and apply more force? Am I even in the ballpark?
 
The ECU reads the resistor value (once every few starts) and makes a small adjustment in the base fuel delivery depending on which resistor it is. Its a common method of making adjustments in embedded (this is a computer that runs some piece of hardware) systems since they have no user interface to tweak things with. Changing the resistors changes a voltage the ECU reads (just like the way it reads the MAP sensor and such) it looks this voltage up in a table and sets a fuel offset factor to whatever it finds. The resistors were intended to provide a way to adjust to differences in pump delivery due to manufacturing tolerances on the assembly line so they would not have to put a custom flash into every ECU (like they often do with big $$$ industrial engines). Putting a #9 in it just takes that adjustment to the max (but does it really? hummm).
Any know what value the chip resistors are?

There's your one free pass for not RTFM'ing :)
 
Quoted from john kennedy's site:

The Stanadyne DS4 pump is fine tuned by a small resistor "chip" that installs inside the wiring cavity of the PMD (pump mounted driver) and slips over the pins. Resistors are available in steps ranging from 1 through 9. Each step in resistor value will alter the fuel delivery by .5mm3. When a pump is built or rebuilt and the calibration is spot-on, it is equipped with a #5 resistor. This is the target value when building a pump. This leaves 4 steps upward to #9 or a 2.0mm3 potential increase in fuel delivery. Based on a 62mm3 program, this is a very slight increase especially when compared to an aftermarket chip or program that runs at 68mm3, 72mm3 or even up to 80mm3!

I have run #5, #9, and #13 resistors, and can assure you that simply swapping them OR using a variable (fuel control) will NOT alter fuel delivery. It WILL do so on the Stanadyne test stand, and it WILL do so upon the resetting or loss of the value stored in the PCM, but will have NO immediate affect.

Case in point: We frequently hear of 6.5 owners having their PMD replaced only to get a DTC 56 (Injection Pump Calibration Resistor Error) several months down the road. This condition will not reset until a proper value resistor is installed.

So what triggers the re-learn of this value? From my observations, initiating TDC learn (scan tool clears PCM memory) will do so. I also surmize that a given number of startups (key cycles) will cause the PCM to "recheck" this resistor.

During development of our laptop scan tool package (94-5 diesel specific) we encountered a table titled "Pump calibration." The vehicle in question had a 115 value logged and was equipped with a #5 resistor. Upon plugging into another driver with a #9 and restarting the engine, the value remained the same. Upon initiating TDC learn, the value changed to 145. Removing the resistor had no effect. TDC learn with no resistor caused the value to change to 95 9and set DTC 56) which is the lowest setting. The aftermarket #13 will also set DTC #56 therfore I will no longer be offering them for sale.

To summarize: I generally recommend the use of a #5 resistor when swapping out drivers. This, being the middle of the road setting, provides a nice safe setting. If one has the ability or desire to have a slight increase in fuel delivery, as evidenced by EGT readings, one could put in the #9 resistor, but remember, it will not change until TDC learn is initiated or the PCM loses its memory.
Click to expand...
 
L98TPI, So for the bulk of us, the easy path is fooling the programming rather than mod the look-up table. Now I got the whole picture, thanks! :cheers2:

Great White, knew about the delayed effect and missed the write-up on Kennedy’s site (or perhaps it is new since I bought the PMD).

Great responses guys. :thumbsup:
 
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