1970s 1979 Seville no injector pulse

[amgsplinter]

My 1979 Seville's ECU sends pulses to the injectors only when engine is off and ingnition is on. Moving the throttle gives nice pulses. When cranking the engine pulses stop and engine wont start.
Replaced already temp sensors, TPS, distributor and checked wiring. 
Only "problem" is that voltage on junction box drops below 10V when cranking.
Can this be the cause of not starting?
Also tried a repLacement ECU but problem remains.

[Cadman-iac]

  I'm not familiar with the system in your car, but have dealt with other newer ones. From your description of symptoms, I would suspect that your ignition switch may be at fault.
Have you checked for voltage from the switch during cranking?

Rick

 Edit: The ignition switch should be sending power to both the ECM and your distributor during both the run and the cranking positions. If you're losing the pulse to the injectors while you're cranking, I would suspect the switch may have a worn contact internally.
 Just a guess based on prior experience.

[TJ Hopland]

I'm not quite clear on what or how you are doing this testing.  With the key just on you are getting injector pulses?  Measured with a test light at the injectors?  Then when you turn the key to crank the light no longer flashers?   And when you move the throttle what is pulsing?

Did this car ever run for you or did it come to you as not running?   Do you still have all the old parts?  You have changed a lot of stuff that seems a little random and with the quality of whats out there today especially for something that was never very common you may have created several new problems by installing possibly bad parts.  Its doubtful that anyone but Bruce has any way to test an ECU.  We have heard of distributors wired backwards.   

I don't know if there was a spec for these systems and voltage but since it doesn't have a micro processor it may not be as sensitive as ones that do to lower voltages.  I think the rough rule was 9v during cranking is considered a problem. 

We do have a couple people here that really know these systems well and repair them and make parts.  Hopefully they will be along soon with some more specifics.  Hopefully none of them are among the ones we are loosing because of new club policies.

[bcroe]

Your ignition (with ESS) working OK?  Put a couple spoonfuls
of gas down the throttle body and it should start to run for a
couple of seconds. 

Those systems should start the engine even at 10V. 
An ECU might not give crank rotation pulses because
the SPEED SENSORS on the HEI are bad, but you already
replaced it.  Check the timing chain slack, or even
for a complete failure.  There is a circuit in the
ECU to inhibit injection pulses if cranking at Wide
Open Throttle.  Unplug the TPS to make sure it is
not shorted to read this, but an internal ECU issue
can also do this (just fixed one of those).   

The ECU could have a bad MAP or other failure to stop
pulses.  You might want to send the ECU here for test
and repair, almost all the 70s Cad ECUs I see at this
age have problems.  Bruce Roe    bcroe@juno.com