I'd like to thank Shane for teaching Electricity 101. Tune in tomorrow,
same bat time, same bat channel, for Electricity 102. Test on Friday! ;-D
Ron
00 PB SLT QC 4X2 5.9 46RE 3.92 LSD
For modifications see my DML Profile (URL follows)
http://www.twistedbits.net/WWWProfile/dakota/Kw9pV1EkFeOYY
-----Original Message-----
From: owner-dakota-truck@buffnet.net
[mailto:owner-dakota-truck@buffnet.net]On Behalf Of Shane Moseley
Sent: Wednesday, July 25, 2001 7:17 PM
To: dakota-truck@buffnet.net
Subject: Re: DML: Engine cranks but not fire on 1999 5.2l PIA
steve preston wrote:
> Yes.You cannot have voltage without current.
Uh - say what? The definition of voltage has nothing to do with current.
It is a potential energy specified in volts. The potential for
current exists. I realize V=IR (Voltage = Current * Resistance) - this is
Ohm's Law. This is a relationship not a definition.
Specifically: "The law stating that the direct current flowing in a
conductor is directly proportional to the potential difference between
its ends."
Current will only flow when the resistance goes down between the terminals.
A short (or no connection between the terminals) represents
almost infinite resistance. In this case - virtually no current is flowing
(I=V/R). You have voltage (or potential for current flow) but
no actual current flowing. A load (like running an electric fan or pump)
applied represents some lower resistance and can initiate current
flow. A wire (or wrench 8) connected directly across the terminals
represents pretty close to 0 resistance which causes full current to
flow from pos to neg. You should get a large spark if the battery is good.
Not near as strong if it is near dead.
> If the battery is at the right voltage unloaded and the
> voltage drops too much when you apply a load,then the
> battery has trouble supplying current.
I agree. The power (P=VI=I^2R) is much less which is caused by low current
(see equation).
<snip>
> Anyway,it seemed odd to me that
> a battery could possibly spin a high-current
> starter,and not go on to also supply low current
> devices.
Consider that charge is stored - and that potential can even rise (due to
chemical reactions) when no load is applied. It is feasible that
enough charge exists to drive the starter and crank the vehicle but enough
of that stored charge is used up that the potential (Volts) and
thus current flow ability is greatly diminished.
> > They are not talking amps it is voltage that the
> > computer is looking at.
The computer is very sensitive to voltage level. It also sound like a crank
or cam position sensor.
Latr,
Shane
-- '96 IndyRam-HisIndy-MPI TB Pulleys RTcam MPComp HVoilpump DynaGearDoubleRoller WindageTray CompTAs '96 IndyRam-HerIndy-numbered(#142)"Track Truck" '74 Triple-Black Dodge Challenger Rallye 360 EFI R&D vehicle '93 Dakota CC 318 - soon to be mine 8)
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