There were a lot of great comments on various forums - here's a synopsis of what feedback I got from my OP:
- OMG it's always the CPS!1!
I was getting a rpm reading, but some people report failed CPS and still have reliable RPM (presumably via crank sensor).. a 30 dollar part that I should have a backup of in the van? I bought the updated International part and put it in.
- with GP on might give insufficient voltage for all the PCM/IDM to come online/sync
Went ahead and replaced the batteries - I was going to do that eventually as my old ones were on the way out.
Fuel Pressure is low:
- transfer pump could be bad
- could be a blockage from sediment, tank crap, or bits of o-rings
On a '96 ~30psi while cranking is acceptable (99-03 should be 50 psi cranking). I was still pretty concerned about the stale old fuel and since it clearly wasn't fuelling, I did a lot of poking around at the return lines, peering into crevasses in the fuel filter bowl, etc. I did actually find some black fibrous material in the screen leading to the pressure regulator, but not enough to be the sole cause of the fuelling issues. (I think it was a scrap of the (slightly ratty) hutch liner).
ICP looks too high:
- ICP sensor failure
- IPR stuck 'open'
I verified the correct function and output values of the ICP Sensor, although disconnecting it *completely failed to generate a code* (This is weird, and something I need to sort out). It also didn't change any of the system behaviour during cranking.
I was worried that the IPR was stuck but after checking some diagrams of the HPO IPR gate and layout, the 'off' (not energized) position of the IPR leaves the drain route open. From what I've read, with the IPR locked in the de-energized position, you would never see > 200psi HPO, which ruled out it being stuck. The duty cycle shown on the graphs falls right into line with the expected numbers - should come up to ~14~ KOEO, and come up to a 45% (max of 54%) on cranking prior to start.
- pulse width looked wrong to some folks, as 2-2.2 ms isn't much injector time
- it's clearly not actually fuelling, so if all above things considered fine, it must be the IDM with some weird error/hardware failure or wiring issue.
I ohm'd out the IDM wiring harness more than once; checked pins, traced stuff around and ended up fixing some abraded bits of harness (unrelated powertrain stuff). Doing a little reading on the startup Pulse Width I discovered the following: 0 ms means the PCM is in the no-sync state (between crank and cps) 0.42ms indicates PCM/IDM sync meaning the PCM waits on ICP to hit minimum cranking pressures (~700psi). At this point, the PW should change to 1-6ms depending on the fuel demand calculations.
It was pissing me off that *everything* looked like appropriate start conditions. I thought I'd like to see some of the result of the 2ms PW for myself, and hooked up a tiny 110V bulb to the B/C pins on the 3/7# connection (I think) and .. no flash, nothing I could see at least.. I then checked the "C" 110VDC pin on Injector harness connection (on the valve gasket) and .. KOEO gave me ~1.1 VDC. Yes, 1/10th of what I expected to see.
This morning I checked the Under Hood Fuse Box (for like, the 4th time) before pulling the IDM harness off again to see if it was getting appropriate voltage. I had previously bench tested the relays, and replaced the PCM relay as it seemed questionable, and this time I just replaced the IDM relay with a new one, and thought I'd give it another 'crank test'.
Bloody thing started; nearly caused my to fall out of the passenger door with my laptop in hand - had expected to log a bit more data of a no-start and instead it ran like a clock. Turned it off, reassembled the intake hoses etc, and cleared a path out of the shop. Started instantly, warmed it, and checked some roadworthiness stuff and half an hour later drove it for 20min or so to let the PCM get reacquainted with the engine.
Runs like a damned clock
I guess I made a key mistake with my assumptions about DTC's and such - there are a multitude of OBD codes that indicate IDM problems and many kind of injector issues; I wasn't getting any, and to all appearances it was a subsystem functioning correctly.
Turns out the relay was partially functioning (ie: primary closes, second makes connection that fails under load). Looked fine to the DMM on the bench - Noting the full voltage/amps behaviour varies from DMM is another mistake I shouldn't have made with a power subsystem.
Ah well, live and learn!
Thanks to all the folks that posted feedback and other resources in this forum; I've learnt a ton
about my van and wouldn't have even tried without the knowledge that other people on these forums can make it happen too!
Some offsite Links that were great: (I hope it's cool if I link em; didn't find this info in many other places)
Ford Diesel Power Forums - View Single Post - No Start 01 7.3
- great little rundown at DMM testing some 'obvious' stuff that your scantool might lie about
- 94 - 03 7.3L Diagnostics on PDF which has some insightful numbers
- More good voltage/resistance values and part numbers