I was tired of buying PMD?s every time my truck started stalling or failed to start.? The electronic DS4 is a fine setup when it is working, but it is very discriminatory when feeding it fuels that are outside the norm of the diesel marketplace.? I went through a couple of IP?s in short order once I started running a modified vegetable oil through my DS4 system.? In another truck, another IP went bad.? That was three strikes.? The trucks ran great, but the optic sensor and related electronics of the DS4 gave me a lot of trouble on the couple of trucks where vegetable oil was used as fuel.?
So, like the military vehicles, I wanted a versatile setup where I could just about run any liquid carbon based fuel in the tank when times get tough and the truck would run.? A multi-fuel truck was what I was after, so after sidelining my truck for several months and reading all information I could find, I have started to retrofit my truck to negate the electronically controlled injector system.?
I chose a DB2 Marine IP and with the marine injectors, I should be on the road and smoking it up with the best of them, doing my part in adding to the ambiance of road travel, smelling like French fries as I go down the road.?
All Theory until it runs: I have gotten strong feedback at every turn regarding this retrofit and the vegetable fuel preparation.? The latter is a subject for another chapter, but through all of this, despite many who would focus on the aggravation and the troubles and offer only little more than the scorn of the naysayer mentality, I have gained great knowledge through all of this!?
The truck is a 1998 K3500 GMC pickup. Let?s look at the DB2 retrofit of the Accelerator Pedal ? Throttle Position Sensor from the later model truck.? My goal is to make this work with transmission control using the stock computer.? The TPS on the older trucks with mechanical injection had 3 wires and one circuit.? The later models with electronic injection and OBII computers have 9 wires and 3 circuits.? The naysayers have jumped up and down stating that this cannot be done without a stand-alone transmission controller.? I am a member of several blog sites and the surprising lack of information and disinformation provides for a frustrating maze for the seeker of real and concrete data.?? We will know soon as to whether the stock ECM will run the transmission without a stand-alone TCM.
DB2 Marine IP set at 250 hp
My original idea to retrofit the drive by wire APP/TPS 9 wire setup did not work because of lack of room.
Plan B: Old type TPS and usage of APP sensor 2 wiring:
I finally rec'd my old type TPS. This thing has a 12 to 4 o'clock rotation (4x that of the APP/TPS - but the IP shaft only turns 12 to 3 o'clock - but the play won't allow tight and continued movement throughout the range of the TPS). There is plenty of adjustment slop in this unit also. There is approximately 2/3 rotation of slop, or 2x 12 to 4 o'clock slop adjustments on each side. This would tend to make me think that the TPS only has available about 1/3 rotation if set all the way to contact upon first throttle movement - and then only on the up side (or down side reversely). It looks (from the literature) that only 1/2 of the movement is needed to provide 4.5V needed at full throttle (if I am correct).
I do not have corresponding info on the APP/TPS unit which I am proposing to use. I think it is similar in output at 5V. That is the input line voltage, so I would guess that that would be max at full throttle.
My next possible option (if the above fails) is to use the TPS from an older truck once I find out the outputs on the older TPS. I want to use the existing computer on my truck because I would also have to install a engine speed sensor (up on the engine similar to the gasser distributor gear) /Oil Pump Drive. I would probably try to take the 9 wire (drive by wire) plug and figuring that it looks like there is a dbl redundency on the TPS output. I wonder if I could splice 6 of the wires for the 5V output and splice them into the 3 wires on the older TPS.
Throttle Position Sensor (TPS)
GM Full-Size Trucks 1988-1998 Repair Information
By monitoring the output voltage from the TPS, the ECM can determine fuel delivery based on throttle valve angle (driver demand).
TESTING
See Figure 1
Backprobe with a high impedance voltmeter at TPS terminals A and B.
With the key ON and engine off, the voltmeter reading should be approximately 5.0 volts.
If the voltage is not as specified, either the wiring to the TPS or the ECM may be faulty. Correct any wiring or ECM faults before continuing test.
Backprobe with a high impedance voltmeter at terminals C and B.
With the key ON and engine off and the throttle closed, the TPS voltage should be approximately 0.5-1.2 volts.
Verify that the TPS voltage increases or decreases smoothly as the throttle is opened or closed. Make sure to open and close the throttle very slowly in order to detect any abnormalities in the TPS voltage reading.
If the sensor voltage is not as specified, replace the sensor.
