moosestang

I get a spike in actual fuel pump voltage during cranking. It shoots up to 25 volts!

Is that even possible?

It does it regardless of tune, but not always. Has anyone ever recorded this anomaly? Maybe it's just a glitch in the sct software.

DTMR

is that that vpwr stands for?

moosestang

I'm not sure. I don't read the abbreviations off the handheld. I'm looking at them in livelink. They are still abbreviated in live link, but not as bad.

Get a PC! I hate my parents apple laptop, it's such a PITA to use. I do like my ipod touch though.

vpwr is probably vehicle power, but I'm not sure if that's guesstimated horsepower or what. VSPD is vehicle speed, pps is pedal position, KSSPK+ is the knock sensor spark adder array, this is what you log to see if the knock sensors are pulling spark.

Nuke

Could it be associated with the fuel pump priming as soon as you turn the key?

moosestang

It's not the fuel pumps priming. I can't start the datalog that fast and it stops datalogging as soon as the key is switched off. It also doesn't log 25 volts at every startup. I didn't think you could get 25 volts on a 12 volt system. There is a fuel pump volts from table pid and it only shows 7.98v when it hits 25, so it's not written in the tune as far as I can tell.

it only happens during cranking, so it's definitely related to start up only. It may be perfectly normal too. My thinking is it's associated with the dual gt500 pumps and they way they are wired, but it should do it every time. Here's a pic of the spike.

hootie_john

Just a wild guess, but is it possible that it is summing the voltages for the twin pumps? Where does it pull the reading from? That might shed some light on it.

moosestang

that's my theory. I'm not sure where it pulls the reading from, but the gt500 pumps have a separate power wire, plus the stock wiring. The spike is right when I turn the key to run. You can see the crank sensor isn't even registering rpms yet.

siggyfreud

Easy way to find out. Go unplug the driver from one of the pumps and start it up.

moosestang

Funny you should mention that. I think one of the drivers might be failing. my fuel pressure has been acting funny, going up and down with small pedal position changes. It's normally pretty steady. I'm going to try switching them. I'll also try unplugging 1 at a time.

May have spoke to soon. Looking at old datalogs, my fuel pressure drop across the injectors does fluctuate between 36-42ish at part throttle. I'll have to do some more data logging.

351Blueblood

Hey Moose can you PM me? I cannot find how to PM you on this site. I have some FP ?'s for you. Thanks Frank