My truck finally runs again. My vp failed and was rigged with an external transistor years ago. Then the dreaded delayed wait to start issues for a long time then the ECM finally died a few months ago. It only ran in the hot wire test mode, idle only. So I made a microcontroller project to do it all. 3 hardware versions and 7 software versions and a lot of simulation and testing later I hooked it up for real today, turned the key and it started and ran, pretty good actually.  I'm  very happy😀. Still a long way to go though. The mysterious VP44 has been cracked.😎

Warm up timing doesn't really count being the timing offset is controlled by IAT and ECT temperatures. Colder the IAT and ECT the more timing will be given to aid in getting to the fuel to vaporize and go bang.

I know it adds timing when cold.I’d have to double check the cold idle timing.  Let me rephrase that. Fully warmed it idles at 13.73 degrees of timing. 

I got the TPS noise settled down. The micro controller I'm using can do analog to digital conversions with no CPU load so instead of supervising the sampling which slows things down, I just let it go randomly and ignore all the samples except the good ones when there is less electrical noise which is before the injection event. That helped a lot. Then I average the samples some too.

I'm pretty stoked to see the youtube video someday  Following this like a hawk haha. I'm hoping to have my custom PCM done this month, then I'll need another project.  I'm thinking transmission control next for me. But man someday I hope to use your work here.  Keep it up mate.

Here are some diagrams I put together that shows how the Vp sensor and solenoid drive current look. There is also the timing ref signal that used to come from the ECM. The vp sensor has two Hall or magneto resistive cells spaced about 1 millimeter apart. I call the signal from the leading cell phase A and the lagging signal phase B. The index tooth causes the A and B to momentarily shift polarity relationship when that occurs I call that tooth edge zero and start a timer at 0 microseconds. At tooth edge 19 the cam rollers go from expanding to compression, that is the cam apex, The inj fuel valve must be closing at that instant, not much before or after that moment.

 

 

 

Started right up this morning 40F no grid heaters. Timing at about 4* at 200 rpm to 400 then 9* and 16*  cold idle.  Almost no smoke. Surged a couple times on first start then soothed out. It likes 10 - 11 warm idle gets rid of some of the rattle. I set the injection duration to 21* for starting plus I can add more manually with the pedal, it takes about 12* of fuel just to idle. It may need more fuel for extreme cold starts. 

Truly fascinating, I'm impressed and wish I could join in with this research. 

So I needed to make the connections on the vp44 more permanent now that I proved it works. I also wasn't sure how much the psg interacts with the internal sensor as far as temperature compensation and bias so I took out the sensor and isolated and did some testing and found it to be quite stable on its own. I modified a defective psg to access the sensor connector and soldered on an old jet ski plug to connect to my project. I almost goofed big time, I put some aluminum foil in the pump so I would not drop the screws in it (still on the motor) and left the foil in there. Had to take the cover off again when I realized it.

On 4/9/2022 at 5:10 PM, W-T said:

Truly fascinating, I'm impressed and wish I could join in with this research. 

Thank you. It's been a big project and a lot of things have been neglected around the house I hope the neighbors don't mind

 

This is so fascinating! Going back to around 2000 guys were wishing someone could "crack the code" on these trucks in hopes of manipulating them better performance.  As far as I know you have gotten further than anyone else with this.

 

The starting-up process intrigues me.  I have always wished VP trucks could start a little more softly, less aggressive fueling and puff of smoke.  For whatever reason the VP pumps seem to totally fall off the table when pulled below idle RPM. May be why VP trucks are the hardest to start in extreme cold.  The very early 98.5 5-speed I had in 1999 would die easy letting out the clutch if you didn't give it a little fuel.  The reflash they did back then fixed it, by making it fuel far more aggressively. 

 

I have wished the idle could be set a little lower on these, 650-700 versus 750-800.

 

More power to you.  I am going to be pulling my VP44 off mine fairly soon and attempting to replace the main fail-prone chip in the PSG.  I've had intermittent long crank issues for the past 3 years and am suspecting the chip. If it cranks and cranks I just shut the key off then it will fire instantly when I retry it.  The VP is a reman of unknown source (previous owner) with about 140,000 miles on it.

First off, welcome to the forum! Head on on over to introductions when you get a moment and say hello.

(edit: hadnt scrolled far enough to see you already did.. Sorry!)

 

My truck has never had issues starting in the cold and I don't plug mine in unless its in the negatives.. My truck starts better than my brother's p24v. The puff of smoke I think is unavoidable because of the mechanical nature of the system. If the crank is swinging and the computer is allowing fuel, then the injectors are getting fuel. no way around that. If it takes longer to fire off then there is fuel pooled in the piston bowl that has to flash off..

 

750-800 is a semi standard idle across almost all vehicles.. What would the benefit to lower idle be?

 

Your 98.5 was probably flashed with the anti stall feature.. Makes a world of difference with a trailer on the back.

 

your hard start sounds more like a priming issue to me.. I would investigate that before ripping a VP apart.

 

Side note how do you like the tubular header? And whos is it?

800 RPM is standard idle speed. If the APPS sensor is tripping the idle validation switch it should be 800 RPM with +/- 10 RPM.

The fish are biting and work is busy so the truck is on the back burner again and fuel costs so much. In extreme cold you only have 2 maybe three tries to start. once the battery voltage falls off the VP simply won't inject. I should have done this 20 years ago. Could have made some money. But I could have never afforded a new truck to hack up and lose the warranty. 

This diagram shows how the crankshaft and camshaft sensors on the early engines are decoded to provide a signal whose falling edge is at 20 degrees after top dead center. The pump uses this reference signal to determine the relationship of its internal sensor, which is attached to the cam ring to the engine position. That's how it calculates timing this value is compared to CAN command timing and the amount of error feeds a servo control loop which changes the duty cycle of the timing control valve which either fills or vents the the timing piston causing it to move against a return spring. If the error is to great for over a certain amount of time P0216 gets thrown. I have a new Tiny Tach with a piezo line clamp on the injection line.  I only bought it for the piezo clamp so I can connect it to my oscilloscope and see when the injector starts spraying. That should be interesting. I think the ECU has a line delay stored inside to really get things dead on. This all seems like overkill considering the P7100 does none of this.

During start up run the lift pump circuit at 50% duty cycle. This will reduce injection pump fuel pressure. It will also prevent over advancement of the pump which creates hard starting. You can verify this by unplugging the lift pump.

Hey all, been super busy lately.  Yes the starting issue I tried disconnecting the lift pump, but the issue only happens occasionally.  So disconnecting the lift pump I wasn't able to repeat it (which could mean that's it, but this issue occurs maybe 5% of the time).  I have a Fuelab pump, it does not like the 50% pulse signal at startup so I have it key-on.  I have a delay relay I'm going to set to 15 seconds and pop in there soon.

 

The startup behavior is odd.  If I begin cranking and it doesn't fire, it will crank and crank and nothing happens.  If I shut the key off a moment then try again it usually lights right off.  Also, it can sit for days and fire instantly.  Other times, I have literally turned shut it off after driving a considerable distance, only to have it crank and crank when starting back up less than 30 seconds later.

 

This problem started about 5 years ago, with my previous lift pump, a Holley, controlled by the ECM.  That pump was about 5psi at startup.

 

Anyway back to the idle subject.  It was much discussed 20 years ago, why the VP trucks idle fairly high compared to 12V trucks in general and Powerstrokes at the time (around 600 as I recall).  To me 800ish has always seemed high.  But not a big deal, more of a curiosity more than anything.

 

I am most of the way through a cam swap on my truck. I decided to chicken out on tearing into my PSG, for now. I may pick up a core sometime for cheap and make an attempt at replacing the chip, keep the pump for a backup.  We'll see.

I would say the 800 rpm idle was chosen because it has less vibration and buzz sent to the truck.  I tried it at 600 and the buzz from the motor was bad

 

Too much fuel pressure at cranking will over advance the timing making nearly impossible to start.

 

Double check the  light is coming on instantly with the key. If the wait to start light isn't coming on it will not start because the fuel pump relay will not power up the VP44 nor any other ECM device till that wait to start lights up. Without the ECM booted up it is dead. It will crank but not start.

Thanks for the tip, I’ll pay attention to the WTS light.

Oh fuel pressure during cranking should be 7 to 12 PSI max. Anything over 12 PSI will cause over advancement and not start hence why there is a relay mod to hold the lift pump off till started for the troublesome cases.

This diagram shows the 2 signals that the speed sensor in the VP produces. The tone wheel on the pump shaft has 6 index regions spaced every 60 degrees. The index teeth have 2 wider then normal teeth with a deeper cut between them. In the diagram notice there is a unique alignment where the B phase is falling below the zero cross dashed line and the A phase is above the line. When the software detects this condition it resets a timer and edge counters. The injection starts at edge 19. By measuring the time between tooth edges, velocity and acceleration can be calculated.  Then applying kinematic equations we can predict edge 19 before it happens. We have to do this because the injection solenoid has deadtime so it has to be energized some time before the injection event is to occur.

 

 

Update the ECM is gone now. The connector was removed and I attached wires to it. The ecm side connector is available new but is expensive to buy only one. This cleaned up the messy wiring a lot. I also made a shielded cable from my VP speed sensor to the controller.  After some testing I found the shield wasn't really necessary.