[V8] battery drain issue

[Kent McLean]

"Steve Kramer" <skramer at mac.com> wrote:
> I'm having a drain on my battery.
> 1. I was rear-ended a few weeks back. ... Does
> the grounding system extend past the battery under the bench?
> 2. I noticed after the accident that I wasn't getting good gas mileage
(260
> to a tank)  I figured the gas tank had been compromised and I wasn't
getting
> enough pressure.
> 3. My left distributor cap is sparking. ... Could a leaking/
> bad distributor cause a drain on the system?

1. The battery is grounded by a strap from the battery negative post
    to the chassis, where the strap bolts to the chassis under the seat.
    The whole chassis acts as a ground.  That means the rear tail lights
    can be attched to ground (the chassis) in the trunk, and the headlights
    can be attached to ground (the chassis) under the hood, etc. So yes,
    the grounding system extends past the battery.

2. If the gas tank has been compromised, such that it couldn't hold
    pressure (not that it is under pressure), that would imply a leak,
   and you should be smelling gas.  The tank is a sealed system.
   The fuel pump pressurizes the fuel in the fuel lines going to the fuel
   injection system.  Also, as gas is consumed, you may find a vacuum
   when you open the gas cap to refill your tank (although I think it is
   vented; I could be wrong here).  I think the poor mileage is related
   to #3.

3. Sparking at the distributor means your spark plugs aren't
   getting 100% of the electricity they need to fire properly, so
   your engine would be down on power.  Which means you are
   asking the other 4 cylinders to work harder to make up for the
   4 that are not getting 100% of their power from the distributor.
   So you gas mileage should be down.  A bad distributor by
   itself wouldn't cause a drain, unless the ignition key was in
   the "run" position.

As for the drain on your battery, there's lots of discussion on the
Audifans archives; search on "battery drain".  Here's one:
<http://www.audifans.com/archives/1997/01/msg01833.html>

In a nutshell, you'll have to chase it down. Remove the positive
cable from the battery, then place an ammeter between the
battery's positive post and the end of the cable.  (If you don't
have an ammeter, you can pick up a Volt-Ohm-Milliammeter
(VOM or multimeter) for cheap at Radio Shack or Sears for
$10-20; more if you want to get fancy).

The meter should show a slight value (about 0.05 amps) due to
keeping the radio memory alive. Anything above that (like 1.5 a)
indicates a drain.  One by one, remove fuses from the fuse box
until the drain goes away.  That isloates the circuit causing the
drain.  Put the fuses back in, and start checking the items that
are protected by the telltale fuse.  For example, you may find
that removing the fuse for the trunk light kills the drain.  You then
discover the trunk light stays on when the truck lid is closed,
caused by a faulty switch. Relace the switch, and the battery
drain problem goes away.  Of course, your problem probably
won't be that simple. :)

HTH,
Kent
'94 100 S Avant
'89 200 TQ, "Bad Puppy"