Ign ECU Q... Where is my start/run voltage going??

440 w/ MP orange box (ballast ohms ~1.6)
Car is hard starting, has been for some time.
WOULD A BAD ECU CAUSE EXCESSIVE DRAW ON START & RUN CIRCUITS???
I take the following readings without my clutch safety switch pressedi in (no starter).

With both ballast resistor leads removed,
the run side gets 12v with ign switch in run &
the coil side gets 12.5v when ign switch is in start

plug the leads to the resistor though, and
RUN is only getting 5v(AT COIL) or so & START is only getting 11v(AT COIL)

What I have been doing, is unplugging one connector from the
ballast resistor. This allows the engine to fire (start)
but not run. Once the cylinders fire, I plug in both sides
of the ballast & the engine starts & runs.

NOTE: When I unplug the ECU, all voltage readings are as would be
expected across the ballast & at the coil.

this is confusing me - "plug the leads to the resistor though, and
run is only getting 5v(AT COIL) or so & run is only getting 11v(AT COIL)". did you mean start is only getting 5v? when you start a car with a ballast the ballast is bypassed entirely and when it starts and you release the key to 'run' then the ballast is being used. is it possible you have these wires reversed at your ign switch?

Sorry,

typo up there.
run is getting 5v at coil.
start is getting 11v at coil.

And the ign switch puts power to .....
coil side, of resistor in start.
run side, of resistor in a run.

Although I should check again that with ign switch in start that both sides
of the resistor should be getting power. I do my voltage checks with the leads off the resistor.

i would either rig up a jumper and bypass the ballast or better still just replace it. those voltage levels seem a tad low but with a 1.6 ballast .

Yea, I only bought 3 more ballast resistors,
none of them are ever what they are advertised (ohm wise).

Jumping out the ballast was one of the first things I
tried to no avail.

When measure voltages with no load (connector unplugged) you should read battery voltage, you are not.

When reading voltage with a load (connector plugged in) you are reading low voltages. Your problem isn't the ECU, it is the supply to the ballast/coil/ECU. Clean up and tighten all you connections, take a voltage measurement at each connection to see where the loss is. I usually start at eh bulkhead connector as that is usually the culprit.

if you jumped it and it made no difference in starting then i'd say you box is headed south. if you jumped and it started id say the ballast is weak. if looks aren't important you can get a parts store ECU from NAPA. if i wanted to keep the general MP ign type and feel but didn't care about looks this is where i would check into that REV-N-ATOR box over in the what's hot/new section. i really like what i've read (i don't believe the huge HP gain though) but i'm happy with my MSD stuff.

I will check the bulkhead & ign switch connection(sa) to the body harness & see if there is a bad connection.

Will let you know.

(THANKS ALL AS ALWAYS)

OK
While I took these readings, the ballast got hot (normal) the ECU got hot but could be held. Should the ECU be hot?

IGN SWITCH IN RUN
bulkhead "N" (which is run) 12v
bulkhead "Q" (which ias run) 5.7v (also an indicator of coil sidevoltage)
IGN switch "BLUE" wire (which is run) 12v
IGN switch "BROWN" wire (which is run) 5.7v (also an indicator of coil side voltage)

IGN SWITCH IN START
bulkhead "N" (which is run) 9v
bulkhead "Q" (which ias run) 11.5v (also aan indicator of coil side voltage)
IGN switch "BLUE" wire (which is run) 9v
IGN switch "BROWN" wire (which is run) 11.8v (also an indicator of coil side voltage)

a hot ECU = a bad thing. warm would be normal but hot, no. that is one of the jobs of the ballast. to reduce current to reduce heat at the ECU and coil.

from experiance when you change control box do the pickup coil at the same time Seen it a dozen times you do one and the other fails.

Quote:

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WOULD A BAD ECU CAUSE EXCESSIVE DRAW ON START & RUN CIRCUITS???

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I would say no. What does the spark look like with the coil wire held 1/4" from ground & someone cranking it with the key? I'd jump 12V directly from the batt positive to the coil positive primary & see if it starts any easier. On a side note the nominal ohms for the orange/chrome boxes is 1.25 ohms but as you noted they're usually higher. When you get this solved if you want to run a lower ohm ballast (plus you have several) get a pair of the double connectors used on the 4 terminal ballast/5 pin ECU systems & the width of (2) 2 terminal ballasts that you have are the right width to fit the connectors side by side. Wire them in parallel & see what you get for ohms. One end has the blue looped wire & you need 2 of them or take the brass connectors out & use new brass ones which is a good idea NAPA 725145. At 1.6 ohms your losing potential spark power but that's not causing the hard starting