| '85 CJ7 repair problem [message #777368] |
Sun, 16 July 2006 23:48 |
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Hey,
I discovered my jeep wouldn't start the other day... the battery was
dead. When I tried to jump it, it wouldn't even turn over - but I
heard a lot of clicking and there was some smoking near the starter
solenoid on the inside fender, passenger side. On closer inspection, I
found some rubber was burning - presumably a short was heating up a
wire up.
Checking the wiring diagram, I found that the previous owner had
removed the fuse links that go from the battery to the alternator,
manifold heater, ignition switch, and a few other things. I couldn't
tell what was shorting so I inserted some 10 amp fuses where the fuse
links would go. One of the fuse links went to the alternator... is 10
amps enough here??
This time, the jump almost worked. She turned over and over for a
while (phew, a big worry gone - the starter motor was fine). Finally,
she caught and started firing, but only for a half asecond. As soon
as the ignition kicked in.
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| Re: '85 CJ7 repair problem [message #784307 ] |
Wed, 19 July 2006 19:27 |
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In-line responses.
Chris Roat wrote:
> I discovered my jeep wouldn't start the other day... the battery was
> dead. When I tried to jump it, it wouldn't even turn over - but I
> heard a lot of clicking and there was some smoking near the starter
> solenoid on the inside fender, passenger side. On closer inspection, I
> found some rubber was burning - presumably a short was heating up a
> wire up.
Probably not a "short", unless you meant the common sense of
"something's not right with the electrical system". My guess is that
the smoke was the result of rust. Rusty connections have high
resistance, resistance under surprisingly small load produces heat
(think light bulb filament here), heat produces smoke.
Apart from the battery cable and starter cable attached to the starter
relay (that black can bolted to the inner right fender) there's only two
wires that run to the relay: One runs to the key switch and sends B(+)
voltage to the relay when you turn the key switch to "Start". The
ground return path is through the mounting bolts to the fender and back
to the battery, so you need good clean connections here.
The other wire runs to the B(+) side of the coil, IIRC. It feeds full
battery power to the coil (as an aid to starting) so long as the key
switch is in the "Start" position. Once the key switch is released to
the "Run" position the relay drops out and voltage to the coil drops to
something around 7 volts via a length of resistor wire loomed into the
OEM harness, or a GM-style resistor block in replacement harnesses.
Are you certain that the battery is dead? This could just be rusty
battery connections at the battery or the relay.
> Checking the wiring diagram, I found that the previous owner had
> removed the fuse links that go from the battery to the alternator,
> manifold heater, ignition switch, and a few other things.
Are you certain? Fusable link looks very much like ordinary primary
wire but the jacket generally isn't bound to the wire strands inside.
Beware too that you didn't shorten the resistor to the coil (inside the
loom, probably in the part that runs across the top of the firewall),
full battery voltage will burn the coil up.
> I couldn't
> tell what was shorting so I inserted some 10 amp fuses where the fuse
> links would go. One of the fuse links went to the alternator... is 10
> amps enough here??
>
> This time, the jump almost worked. She turned over and over for a
> while (phew, a big worry gone - the starter motor was fine).
Failed Ford starters don't generally click, they usually don't do
/anything/ when they fail. Or, if the Bendix drive fails (had one once)
they spin up and whine, but nothing else.
> Finally,
> she caught and started firing, but only for a half asecond. As soon
> as the ignition kicked in.
I'll bet that it was "as soon as I released the key" and the relay
stopped sending full voltage to the coil. With the engine not running
and the key switch in the "run" position check the voltage from the coil
B(+) terminal to a good ground, you should get something lower than 12
volts.
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