cranking but no fire
 

Have a 83 mercruiser i/o 3.0l in a wellcraft. did a little maintance
on it getting ready for the season. The starter was acting up last
year and i pulled it and put in a new one. It is cranking fine, hits
good and hard every time. But i was getting no fire. I stated at the
plugs and traced back to see if i can see a spark. ended up at a bad
coil. Pulled it and heard the swishing sound, so unless the coil on a
marine motor is diffrent it's eletolitic fluid menbrane had busted.
replaced it with a coil form auto zone. Here is my problem, we still
have no spark
Pulled the volt meter out and found this:
With the key off:
we have nothing on the + 0.0v
we have nothing on the - 0.0
With the key in the on position:
we have 12v on the +
!!! we have 12v on the -
From my understanding, and without a service/maintenance manual on
hand,I believe this to be very wrong. Has something changed with the
starter cylanoid?
with all the wires on the cylanoid, there are only 2 that fit the
smaller poles. Tried reversing them, and got no cranking. So they are
in the correct postition. I did notice a momentary firing when i first
started the engine after putting the starter in, but nothing since
then. Any help would be greatly appreciated.
TIA, JAW

cranking but no fire
 

"jason" wrote in message
om...
Have a 83 mercruiser i/o 3.0l in a wellcraft. did a little maintance
on it getting ready for the season. The starter was acting up last
year and i pulled it and put in a new one. It is cranking fine, hits
good and hard every time. But i was getting no fire. I stated at the
plugs and traced back to see if i can see a spark. ended up at a bad
coil. Pulled it and heard the swishing sound, so unless the coil on a
marine motor is diffrent it's eletolitic fluid menbrane had busted.
replaced it with a coil form auto zone. Here is my problem, we still
have no spark
Pulled the volt meter out and found this:
With the key off:
we have nothing on the + 0.0v
we have nothing on the - 0.0
With the key in the on position:
we have 12v on the +
!!! we have 12v on the -
From my understanding, and without a service/maintenance manual on
hand,I believe this to be very wrong. Has something changed with the
starter cylanoid?
with all the wires on the cylanoid, there are only 2 that fit the
smaller poles. Tried reversing them, and got no cranking. So they are
in the correct postition. I did notice a momentary firing when i first
started the engine after putting the starter in, but nothing since
then. Any help would be greatly appreciated.
TIA, JAW

If the points are open, you will get 12v on both terminals. As you turn
over the engine, the (-) terminal should go between 12v and 0v. You can see
if there is spark, by grounding the (-) terminal that goes to the
distributor. When you remove the ground, you should get a spark. Pull the
distributor cap and see if the rotor is turning and the points are opening
and closing.
Bill

cranking but no fire
 

With the key in the on position:
we have 12v on the +
!!! we have 12v on the -

Points? Electronic?

The points/electronics are what provides the ground to the coil.

cranking but no fire
 

"jason" wrote in message
om...
Have a 83 mercruiser i/o 3.0l in a wellcraft. did a little maintance
on it getting ready for the season. The starter was acting up last
year and i pulled it and put in a new one. It is cranking fine, hits
good and hard every time. But i was getting no fire. I stated at the
plugs and traced back to see if i can see a spark. ended up at a bad
coil. Pulled it and heard the swishing sound, so unless the coil on a
marine motor is diffrent it's eletolitic fluid menbrane had busted.
replaced it with a coil form auto zone. Here is my problem, we still
have no spark
Pulled the volt meter out and found this:
With the key off:
we have nothing on the + 0.0v
we have nothing on the - 0.0
With the key in the on position:
we have 12v on the +
!!! we have 12v on the -
From my understanding, and without a service/maintenance manual on
hand,I believe this to be very wrong. Has something changed with the
starter cylanoid?
with all the wires on the cylanoid, there are only 2 that fit the
smaller poles. Tried reversing them, and got no cranking. So they are
in the correct postition. I did notice a momentary firing when i first
started the engine after putting the starter in, but nothing since
then. Any help would be greatly appreciated.
TIA, JAW

I gather that you are looking at the coil terminals. One lead, the + is
connected to the ign switch, the other the - post is connected to the points
in the Distributor, or the electronic ignition module. The - terminal is
pulled low then high in time to fire the cyl the rotor is positioned under
in the dist cap. The rate of change in the primary voltage determines the
secondary (along with turns ratio).

cranking but no fire
 

"Calif Bill" wrote in message hlink.net...
"jason" wrote in message
om...
Have a 83 mercruiser i/o 3.0l in a wellcraft. did a little maintance
on it getting ready for the season. The starter was acting up last
year and i pulled it and put in a new one. It is cranking fine, hits
good and hard every time. But i was getting no fire. I stated at the
plugs and traced back to see if i can see a spark. ended up at a bad
coil. Pulled it and heard the swishing sound, so unless the coil on a
marine motor is diffrent it's eletolitic fluid menbrane had busted.
replaced it with a coil form auto zone. Here is my problem, we still
have no spark
Pulled the volt meter out and found this:
With the key off:
we have nothing on the + 0.0v
we have nothing on the - 0.0
With the key in the on position:
we have 12v on the +
!!! we have 12v on the -
From my understanding, and without a service/maintenance manual on
hand,I believe this to be very wrong. Has something changed with the
starter cylanoid?
with all the wires on the cylanoid, there are only 2 that fit the
smaller poles. Tried reversing them, and got no cranking. So they are
in the correct postition. I did notice a momentary firing when i first
started the engine after putting the starter in, but nothing since
then. Any help would be greatly appreciated.
TIA, JAW

If the points are open, you will get 12v on both terminals. As you turn
over the engine, the (-) terminal should go between 12v and 0v. You can see
if there is spark, by grounding the (-) terminal that goes to the
distributor. When you remove the ground, you should get a spark. Pull the
distributor cap and see if the rotor is turning and the points are opening
and closing.
Bill

Bill - there are 4 wires in question, 2 that are fixed together on the
+ side and 2 loose on the - side. not sure of the color pattern on
the + side, but the - has a gray and a black. With the key in the on
position and all wires disconnected from the coil. i see 12 on the
pair and 12 on the gray and 0 on the black. the black leades down to
underneath the distributer. I will test your hint when i retun home
and see if the rotor is spinning. i and guessing that it will not be
the case. Can i crank the motor with the cap off the distributer to
see it spin?

cranking but no fire
 

Assuming this engine has points, if you are measuring across the coil, you
will not get an accurate reading.

The + side of the coil should be hot when the ignition is on, but only when
measured to ground...NOT the - side of the coil.

The - side of the coil is connected to the points. When the points are
"open" the coil is being saturated. When the points close, the field
collapses, and make the voltage (spark).

A shorted condenser will render an ignition system useless. An open
condenser, will cause huge arcing on the point face, and can wipe out a set
of points in minutes.

Also, some models had a ballast resistor running from the primary side of
the starter, to the coil. This was used to keep the current down across the
points, during cranking.

I have always replaced my "point distributors" in all my boats, to
"pointless" electronic units...you might want to consider the same...your GM
would take an HEI replacement unit, and it is a simple swap. The coil pack
is incorporated in the distributor cap, and it is a simple two wire hook up.
One lead is + voltage from the ignition key, and the other is tach pulse (if
used).

Hope this helps some, good luck.

--
-Netsock

"It's just about going fast...that's all..."
http://home.insight.rr.com/cgreen/

cranking but no fire
 

Bingo -- replaced the condincer and we got fire. still a little
slugis, so i drained the tank and droped fresh midgrade and then
changed the plugs
she is running great
taking her out tomorrow
Thanks
JAW


"Netsock" wrote in message ...
Assuming this engine has points, if you are measuring across the coil, you
will not get an accurate reading.

The + side of the coil should be hot when the ignition is on, but only when
measured to ground...NOT the - side of the coil.

The - side of the coil is connected to the points. When the points are
"open" the coil is being saturated. When the points close, the field
collapses, and make the voltage (spark).

A shorted condenser will render an ignition system useless. An open
condenser, will cause huge arcing on the point face, and can wipe out a set
of points in minutes.

Also, some models had a ballast resistor running from the primary side of
the starter, to the coil. This was used to keep the current down across the
points, during cranking.

I have always replaced my "point distributors" in all my boats, to
"pointless" electronic units...you might want to consider the same...your GM
would take an HEI replacement unit, and it is a simple swap. The coil pack
is incorporated in the distributor cap, and it is a simple two wire hook up.
One lead is + voltage from the ignition key, and the other is tach pulse (if
used).

Hope this helps some, good luck.

cranking but no fire
 

On 24 Jul 2004 21:43:06 -0700, (jason) wrote:
Bingo -- replaced the condincer and we got fire. still a little
slugis, so i drained the tank and droped fresh midgrade and then
changed the plugs
she is running great
taking her out tomorrow
Thanks
JAW
=========================

If the condenser was bad, good chance the points need to be replaced
also. Check your timing when you're done with that.

cranking but no fire
 

Glad I could help, but Wayne is right...you should ALWAYS replace the
condenser when replacing the points, and vive versa.

--
-Netsock

"It's just about going fast...that's all..."
http://home.insight.rr.com/cgreen/
"jason" wrote in message
...
Bingo -- replaced the condincer and we got fire. still a little
slugis, so i drained the tank and droped fresh midgrade and then
changed the plugs
she is running great
taking her out tomorrow
Thanks
JAW

cranking but no fire
 

"Netsock" wrote in message
...


The - side of the coil is connected to the points. When the points are
"open" the coil is being saturated. When the points close, the field
collapses, and make the voltage (spark).

You have this backwards....

When the points close current is allowed to flow, but current builds slowly.
At low RPMs the current will reach some maximum level deteremined by the
voltage and resistance of the coil.

When the points open the current path is altered. A basic principle of a
coil is that it is impossible for the current to change instantaneously, it
has to go someplace. As the points first start to open it will divert into
the condensor, which gives the points time to open far enough that the spark
won't jump the points. The VERY rapid rise in voltage across the condenser
is also coupled via a transformer action to the "secondary" winding which
generates the spark voltage.


Rod