Billgran wrote:
"Per-Olof Litby" wrote in message
...

I made a post back in January about my non-starting Cobra (GM block,
original post at bottom) and received some responses. It's now spring time
and the problem has not fixed itself :-) so it's time to revisit it. I've
done some more troubleshooting and it indicates a more general electrical
problem.

I've found that the trim does NOT work either, and that as soon as I
switch on something, say the engine room blower, there is a significant
voltage drop - down to below 6V. The gauges don't power up fully and the
tachometer doesn't return to 0 when the ignition switch is put in the acc.
position.

Voltage drops to zero when I try to operate the trim or the starter, and
the trim solenoids don't click.

Also, there is no voltage on the IGN lead which goes from the ignition
switch to the tach. With the ignition switch in the start position, there
is only about 6V on the purple lead at the starter solenoid (which is
placed on the starter motor).

Battery is new and OK. I've checked all fuses I know of, and there is
power from the battery to the instrument panel (12V).

Any ideas? Grounding problem at the ignition switch?

/P O Litby




Your voltage drop is possibley due to a bad battery cable, poor connection,
or internal corrosion.

Grab the battery cables and flex them along their length. If you feel any
"crunchy" areas, they are corroded internally. Inspect the ground stud on
the back of the motor. Usually water drips down thru the engine cover to
transom area and rusts the stud and terminals. Look closely for rust and
corrosion around wiring or their connectors and fuse holders.

A voltage drop test using a voltmeter will tell you where the problem is.
Read a service manual or enlist the help of a knowledgeable person to
perform it.

Bill Grannis
service manager



OK, this thing is giving me gray hairs. I've done the voltage drop test,
and the voltage drop (which varies depending on what you switch on, from
a 2-3 volt drop with the cabin lights on to a 6-7 volt drop with the
ignition key in the start position) actually starts at the battery
positive terminal and remains the same at other points forward.

Measuring directly between the battery terminals, the voltage drop is
right there whenever something is switched on.

The trim solenoids (just barely) trigger when a direct lead from the
positive battery terminal is connected to their trigger terminal. The
starter solenoid does not (suspect it needs more current). Doing this
drops the voltage (direct at battery) down to 6 volts.

All ground points (I tested several) have the same potential as the
negative battery terminal, so ground seems fine from that point of view.
The main ground wire from the negative battery terminal to the engine
ground point seems OK, no obvious corrosion or damage.

So this to me indicates either a faulty battery - which seems strange
since I tried a different battery last fall when the problem showed up
the first time and that didn't help - or some problem with the grounding.

Am I correct?

/POL