Another 740T problem, Arg

  • Thread starter Thread starter James Sweet
  • Start date Start date
J

James Sweet

After years of faithful service my '87 740T has left me stranded for the
first time, thankfully only a mile from my house so I was able to walk
home. I was driving through a parking lot and the tachometer needle
suddenly wigged out and was flipping all over the place for a moment
then the engine simply shut off. Now it turns over fine but doesn't even
try to start. I can hear the fuel pump running for a fraction of a
second after I stop cranking but the tach needle now just sits at zero
and doesn't budge. My first guess is the hall effect sensor in the
distributor but before I spend $50 on a new one I'd like some confirmation.

Also does anyone have experience with the aftermarket hall sensors FCP
Groton sells? The OEM Bosch sensor is nearly twice the cost.
 
After years of faithful service my '87 740T has left me stranded for the
first time, thankfully only a mile from my house so I was able to walk
home. I was driving through a parking lot and the tachometer needle
suddenly wigged out and was flipping all over the place for a moment
then the engine simply shut off. Now it turns over fine but doesn't even
try to start. I can hear the fuel pump running for a fraction of a
second after I stop cranking but the tach needle now just sits at zero
and doesn't budge. My first guess is the hall effect sensor in the
distributor but before I spend $50 on a new one I'd like some confirmation.

Also does anyone have experience with the aftermarket hall sensors FCP
Groton sells? The OEM Bosch sensor is nearly twice the cost.
Click to expand...
I'd o some more testing first, but that's exactly the way the '87 EZK
control units would fail back in '87. They had a very high failure rate
for a few production weeks. If you drop the box down from its bracket by
the steering column and tap the tic-tac-toe pattern on the case in the
center square with the plastic end of a #2 Phillips screw driver while
an assistant cranks the motor and watches the tach you may see the
needle jump erratically to confirm a bad joint/component that lives
right in the center of the PCB for the EZK box.

Bob
 
I'd o some more testing first, but that's exactly the way the '87 EZK
control units would fail back in '87. They had a very high failure rate
for a few production weeks. If you drop the box down from its bracket by
the steering column and tap the tic-tac-toe pattern on the case in the
center square with the plastic end of a #2 Phillips screw driver while
an assistant cranks the motor and watches the tach you may see the
needle jump erratically to confirm a bad joint/component that lives
right in the center of the PCB for the EZK box.

Bob
Click to expand...



Thanks for the suggestion, I actually have a spare ignition box
somewhere, I should drag that out and plug it in. That would rock if it
were just a solder joint, I can fix that easily enough. Is there any
good way to test the hall sensor? I don't know what the pinout is.
 
You must log in or register to reply here.
Back
Top