Last week I posted symptoms of "660T CRANKSFINEBUTNOSTART" for my 1987 760FT. I checked all components I knew about, through brickboard archives and the dreaded haynes manual (its like getting half a manual).

an early reply to my brickboard posting by chris bogue, plus my mechanic’s intuition, led to distributor as culprit. More precisely, the culprit turned out to be the hall effect sensor. Not the distributor, not the hall sensor connector, not the wires, but in the sensor itself, or where the wires connect inside the sensor.

Well, as of yesterday evening, after securing a new/old distributor, the car is now its old ROARING self!

So, as a public service, my mechanic, andy, agreed to put his wisdom in words via email, re: his tests which verified hall effect sensor fault. the epitaph follows in andy’s words:

"Diagnostics on the Volvo were unfortunately intuitive - the troubleshooting trees that are published were written when the systems were new, and no shortcuts were designed into them for *most chronic* problems. I would still be working my way through crap like "alt belt tension" if I had followed the book.

No spark

12V on both sides of coil primary

Noid light - no inj pulse

12V (through ballast, possibly 10V?) both sides of injectors

Energize fuel pumps, key on, still no pulse or spark

What pulses both? dist or crank sensor(depending on year)

remove dist cap, check rotor turning, T belt ok

Search shop for known OK hall-effect Bosch dist, find Saab 900 unit

check wiring connectors for + 0 -

make left gonad available to anyone with a Saab 900 distrib elec connector -

no luck

adapt Volvo dist connector to fit Saab dist, incl ground, rotate with key on,

Bingo.

remove Volvo distrib, connect wiring, rotate, no spark, etc

re-wire Saab distrib, rotate, Bingo again - *Volvo Hall effect NG*

Additional -

Testing the two hall effects side-by-side showed identical ohms through each, with some diode-like effect noted from each (ohms changes with meter polarity). Any BBoard xperts able to bench-test a hall effect, I'd be interested in how.

Andy"

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Thanks to you brickboarders for your thoughts and input on this no-start situation. Now, for the next challenge, my son called me to say his ’83 242 cranks, but won’t start. Go figure – well at least we will know where to start on the troubleshoot!