Long crank time, but what is FUELPW doing?

[GregH]

Ok, so I've got an '06 in for a long crank time. Pretty straightforward, slow to build ICP, P2291 present in memory, and the hotter the oil, the longer it takes to start.

 

But I was watching some data, and had FUELPW up as one of the PIDs - having just come off the cluster that is my '03 long crank time that recieved a short block...

 

FUELPW pulses to about 3ms for a short time - almost like the computer is trying to bump up the cranking speed with some sort of burn, however crappy the injection would be at low ICP. It looks like the ICP slowly rams to the 300ish range, pretty much stabilizes there, then the computer goes ahead and pops the injectors a few times with a long pulse width. This injects some fuel into the cylinders, it burns, and bumps the cranking speed up enough to allow the high pressure pump to overcome the leaks. I observed the cranking speed bump up from 170's to 220's.

 

Check out the capture:

 

 

Interesting stuff...

[slim]

Can you upload the IDS recording to the internet? Just wondering, because it would be easier to view on my computer. But I was just wondering what ICP pressure is at when the computer enables the injectors. It may be borderline and that's why the FuelPW is on/off. I have seen injectors enable below 500 psi before which is contrary to what we have been told.

[Jim Warman]

It's always possible that there's something in PCM strategy that we aren't privvy to.... But the neanderthal in me wants to cut my PID list down to ICP_V and FUEL_PW to see if ICP has anything hiding in between data scans....

 

I don't really expect to see anything, but I feel the need to look....

 

Just so I know.... this IS two cranking events back to back, right?

[Keith Browning]

In addition to that, should you make another screen shot, move the time marker to a spot where you are cranking, maybe where the FUELPW is cutting out. This way we can read the PID values at the time of highest suspicion.