Help! No Start: '88 GM 2.8L MPI V-6

[Ferrill, Jess B]

I hope I am not misusing the DIY_ EFI with a mundane service problem on
a totally stock car, but it's got me stumped :<(.  Thanks for your
patience and help. 

My daughter's 1988 Oldsmobile Cutlass Supreme 2 dr.(same as Chev Lumina,
Buick Regal, Pontiac Gran Prix) with 2.8 L V-6 Multi-Port Injection
(Auto Trans & FrtWD) would not start after sitting several days.
Battery was low ("click, click" she said describing solenoid sound).
Engine would still not fire after attempting jump start and re-charging
battery.  Fuel pump, filter and system was priming and ok; see 40 psi at
the fuel rail, pressure regulator works ok dropping 5 - 10 psi when
vacuum is applied.  Spark is good and healthy, jumps 0.100" gap easily
and regularly. Car ran well before no start problem, except for
occasional stall when first started from cold, has 109K miles. 

Car will run for a second if the ignition is turned on to run fuel pump
and pressurize fuel rail, then pulse injectors with 12 volts, then
attempt start. Grounding "A" to "B" on ALDL to check for ECM trouble
codes yielded only the usual "12" s. (Indicating ECM is in Diagnostic
mode), but no other codes.  

Connecting an LED indicator across the injectors showed no flashes while
attempting start. Injectors were getting 12 volts power from ignition
key switch, but the ECM was not providing the pulses to ground through
its' internal injector driver.  "Oh this will be easy" says the
confident father!  "Looks like a bad injector driver in the ECM!"
(Impress daughter with the technical talk, right?)  (P4 ECM #1227727
upgraded with speed density, has ASWH MEM-CAL).  Plunked down $80 to
replace ECM with remanufactured unit.  Checked all solenoids for
resistance (All above 20 ohms).  MEM-CAL transferred from old ECM.  All
ECM and MEM-CAL connector contacts cleaned; no corrosion or
discoloration.  MEM-CAL chips seated ok.

But all symptoms were exactly the same with the "new"  ECM:  Injectors
not being pulsed, only "12" trouble code. Not the ECM?  Plugged and
unplugged all the sensors.  Checked most sensors from the ECM
connectors, everything looks ok.  All fuses have been pulled, checked
and cleaned. Most but not all connectors have been unplugged, examined
for corrosion and replugged.  Both banks (1,3,5 & 2,4,6) have the same
problem.  The injectors are 12 ohms, and I see the expected 4 ohms
across each bank of three in parallel. 

Grounds look ok, except possibly sensor (EGR, MAT, MAP, Coolant Temp,
TPS) grounds (looking at C5 & C10 in harness) are not grounded to engine
(which one Chilton Diagnostic Chart for EGR, Code 32, says should be
grounded to engine, but Haynes and the rest of the Chilton charts do not
show grounded).  Looking from EGR terminal "C" back towards ECM
connector harness I see a solid ground to engine (the questionable
ground?) but open to C5/C10 harness terminals (all the charts say this
should show continuity).  The rest of the sensors (MAP, MAT, etc.) have
correct continuity back to C5/C10.  This thing is a bear to work on for
access so it is difficult to trace and open the harness covers to check
for opens/damage or confirm the C5/C10 ground.

I can disconnect most sensors and the gray and black mini-harness
connectors and it still shows only "12" trouble codes.  Is this normal
if the engine can't be run?

Summary:  After sitting with low battery and jump start/recharge,
injectors are not getting pulsed, 12 volts is present to injectors, ECM
has been replaced.  Car will run briefly if injectors are operated with
separate 12 volts.  There may be a problem with sensor grounds.

My questions for the group:

1)  Any ideas?

2)  When a GM P4 ECM car will not run, can the ECM set any trouble
codes?  (I tried turning on ignition for 15 seconds and cranking for 15
seconds more which was supposed to set codes on some early GM ECMs, but
still get only "12"s).

3)   What are the minimum sensor inputs required to the ECM to make it
provide the ground pulses for the injectors? 

4)  Can the MEM-CAL (which was not replaced, only transferred from the
old ECM) cause this problem and still have the ECM show "12" codes?

5)   The question as to whether C5/C10 should be grounded to the engine
is still unanswered  and is where I am concentrating my efforts.  If the
analog type EGR doesn't get a ground for its pintle position sensor will
this prevent the injectors from being fired?  If the C5/C10 sensor
ground is not grounded to the engine will this prevent the injectors
from firing?  (I don't want to just ground C5/C10 and try it until I am
sure that this is not supposed to be a floating or instrument ground).
I don't want to spend too much time in this area if it can't cause
problem.

Thanks everyone for your help,  I will post the solution when I find it.

Britt Ferrill
bferrill at amp.com
910+727-5387