ignition ground

Bought a 1987 Olds Firenza GT with 40K miles that had been in storage
for several years. Looks great but I've had a series of electrical
problems (it is entirely possible that my "fix" of one leads to the
next). In order, I've replaced the knock sensor, the ignition module,
plugs and wires, the alternator, one of the three coils and most
recently the starter. After every "fix" the car runs great --- then a
new problem.

Shortly after replacing the starter I've run into a new problem that I
can't figure out. The car won't start 80% of the time (warm or cold).
In attempting to start it will sometimes backfire significantly. The
other 20% of the time it starts and runs like a champ. In trying to
isolate the problem, I pulled one of the plug wires and stuck a
screwdriver in it and attempted to draw an arc to the engine block to
see if there was a spark - nothing. But this is the weird part: I
accidentally touched the screwdriver to the block and the car
immediately started and then of course the plug wire was arcing
strongly. I tried it again and the same thing happened. When I just put
the wire back on the plug, the car won't start.

It seems like I must be grounding the ignition system which must
otherwise be ungrounded. Could this be caused by my work on the starter
or ICM? They are both extremely hard to see and to get to so I'm never
100% sure of the quality of my work.

Jeff

I am starting to sound like a broken record, but I would first make sure
the engine has a ground to the body. Ghost troubles can lots of times
be traced to a system lacking a main ground so it steals it for a while
until something moves. I have seen gas pedal cables be the ground so it
would only start with the pedal in a certain place.

There is usually a wire mesh strap from the back or side of the engine
to the firewall. These rot a lot up here in the salt belt so I see it
lots.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Jeff C wrote:
>
> Bought a 1987 Olds Firenza GT with 40K miles that had been in storage
> for several years. Looks great but I've had a series of electrical
> problems (it is entirely possible that my "fix" of one leads to the
> next). In order, I've replaced the knock sensor, the ignition module,
> plugs and wires, the alternator, one of the three coils and most
> recently the starter. After every "fix" the car runs great --- then a
> new problem.
>
> Shortly after replacing the starter I've run into a new problem that I
> can't figure out. The car won't start 80% of the time (warm or cold).
> In attempting to start it will sometimes backfire significantly. The
> other 20% of the time it starts and runs like a champ. In trying to
> isolate the problem, I pulled one of the plug wires and stuck a
> screwdriver in it and attempted to draw an arc to the engine block to
> see if there was a spark - nothing. But this is the weird part: I
> accidentally touched the screwdriver to the block and the car
> immediately started and then of course the plug wire was arcing
> strongly. I tried it again and the same thing happened. When I just put
> the wire back on the plug, the car won't start.
>
> It seems like I must be grounding the ignition system which must
> otherwise be ungrounded. Could this be caused by my work on the starter
> or ICM? They are both extremely hard to see and to get to so I'm never
> 100% sure of the quality of my work.
>
> Jeff

"Jeff C" > wrote

> Bought a 1987 Olds Firenza GT with 40K miles that had been in storage...
> Shortly after replacing the starter I've run into a new problem that I
> can't figure out. The car won't start 80% of the time (warm or cold).
> In attempting to start it will sometimes backfire significantly. The
> other 20% of the time it starts and runs like a champ. In trying to
> isolate the problem, I pulled one of the plug wires and stuck a
> screwdriver in it and attempted to draw an arc to the engine block to
> see if there was a spark - nothing. But this is the weird part: I
> accidentally touched the screwdriver to the block and the car
> immediately started and then of course the plug wire was arcing
> strongly. I tried it again and the same thing happened. When I just put
> the wire back on the plug, the car won't start. <snip>
> It seems like I must be grounding the ignition system which must
> otherwise be ungrounded. Could this be caused by my work on the starter
> or ICM? Jeff

It sounds as though you have a waste spark system where if one
of the secondary grounds you will have a much stronger spark on the
other secondary port. For example, you have a coil per two
plugs. If one plugs wire touches grounds then the other plug will
generate a stronger spark, jumping the plug gap, which otherwise
would not occur if the plug(s) gaps are set too wide, voltage too low,
coil too old and/or the compression too high. Once started, the plug
wire arcs strongly because battery voltage increases. This may
not be your problem but make sense to me.

--
Squareman