Re: [ihc] Coil Voltage?

[John Hofstetter <hofs@xxxxxxxxxxxx>]

on 3/19/04 1:37 PM, George B Humphrey at xgbhx@domain.elided wrote:

> I want to use the positive side of the coil as the trigger for the relay
> to the Projection system. I'm not getting enough current to the fast idle
> solenoid during start up and the solenoid recoils during cranking. I
> tried setting it up this way and can not get it to work at all. The fuel
> pump won't even prime. I checked the voltage across the coil (Pertronix
> Flame Thrower) while the ignition is in the start position and the engine
> is not running and only get 4.2 volts. I assume I should get full
> voltage. Is that correct? If so, does anyone have an idea why I am not?
> Once started the 345 runs beautifully. If 4.2 volts is about right, what
> do I need to do to get the Projection to trigger from the coil? As you
> can tell my auto electric knowledge is only slightly above none at all.
> 
> George H.
> 72 Scout II
> 345 V8

George,

I'm a little confused. You want to use the positive terminal on the coil as
the TRIGGER for the relay to the Pro-jection. Well, the voltage across the
coil is irrelevant in this case, as the voltage between the positive
terminal and the ground is what is relevant. So, you turn on the key, and
the voltage from the positive terminal goes through the relay to GROUND (all
important!) which  closes the relay which then takes current directly from
the battery to supply the fuel pump, the fast idle solenoid and whatever
else the ECCU tells it to supply. The voltage from the coil is not relevant
as long as it will close the relay. The negative terminal on the coil is
used as the tach signal, but not as the ground to the relay, or to anything
else. 

Most all problems with the Pro-jection, if it is wired correctly, are caused
by bad grounds. 

Hope this helps. 

John

John Hofstetter
www.goldrush.com/~hofs