'88 760 B230FT distributor

  • Thread starter Thread starter Anthony Flint
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Anthony Flint

Well, here's one I've not been able to figure out...

Problem:
Overnight-cold engine, when started, misses sporadically. While testing
spark w/timing light, noticed that when it was missing, the timing light
followed suit. New cap, rotor, plugs, wires, 3 different ignition modules
failed to clear problem. Retested using timing light and found that same
results acheived by connecting trigger lead to power supply of coil, which
meant the coil wasn't being triggered correctly. Since 3 ignition modules
acted the same, that pretty much ruled them out.

That left the hall effect switch. Pulled the distributor off the engine and
took a peek. Light film of oil, so internal seal is going/gone.

What really got my attention though is the plastic ring which holds down the
wires going from the connector on the edge of the distro base to the hall
switch... it was mostly gone, and what little was left was melted and
dripping down!

Engine hasn't shown any signs of overheating. Any idea what might have
caused this?

Thanks!
Tony
 
Anthony Flint said:
Well, here's one I've not been able to figure out...

Problem:
Overnight-cold engine, when started, misses sporadically. While testing
spark w/timing light, noticed that when it was missing, the timing light
followed suit. New cap, rotor, plugs, wires, 3 different ignition modules
failed to clear problem. Retested using timing light and found that same
results acheived by connecting trigger lead to power supply of coil, which
meant the coil wasn't being triggered correctly. Since 3 ignition modules
acted the same, that pretty much ruled them out.

That left the hall effect switch. Pulled the distributor off the engine and
took a peek. Light film of oil, so internal seal is going/gone.
Click to expand...

I have a 95 940 Turbo with end of head on the camshaft distributor, it also
get a light film of oil, but it just makes the car hesitate a little. I
find all cam mounted distributors do this. The 940 has an effective looking
metal seal on the disti base, compared the 340 1.7 that was really bad, but
the 940 still leaks.
What really got my attention though is the plastic ring which holds down the
wires going from the connector on the edge of the distro base to the hall
switch... it was mostly gone, and what little was left was melted and
dripping down!
Click to expand...
Weird, I assume it was hot, must be getting/taking too much current. Not
seen any melted wire on overheaded engines before.
My car doesn't use a hall effect, but they generally work by passing a
current through a semi-conductor which conducts a bit more when exposed to a
magnetic field. Could be a faulty hall sensor that is consuming more
current than usual but still functioning as it is probably the current /
voltage change that triggers the ignition.
 
I used to have a 1988 740 with the distributor with the hall effect sensor
in it. I'm pretty sure my motor had been overheated at some stage before I
got it (new water pump - shiny clean head etc).

I'd had it about 8 months and after washing it and driving it into my garage
one day it died. Turned out that the plastic cable clamp had been damaged,
I assumed by the previous overheating and pieces had broken been caught by
the rotating cup and smashed the hall effect device. It just took a while
for it to happen! The hall sensor still worked but it's casing was smashed
and un-usable. So I bought a used distributor. It wasn't easy to find,
apparantly Volvo only used the sensor in the 740 distributor for a couple of
years.

My advice to anyone with the model with the hall effect sensor would be to
check the condition of the plastic cable clamp occasionally and fix it if it
looks damaged as it can stop your car - suddenly. Rip it out and clamp the
wires some other way if necessary.

Regards
Barry
 
Well, got it all fixed.

Replaced the distributor, but problem remained. Replaced plug wires...
problem fixed. And they're barely a year old!

What was really strange is that as the engine warmed up, the problem faded,
though not completely. What finally gave it away was a post (somewhere)
about weak spark under acceleration. Spark might be fine at idle, but as
speed and pressure increased, the wires just couldn't handle it.

FYI.

Tony
 
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