High tension cable sparks once only

My 1980 Volvo DL engine stopped suddenly while driving, and wouldn't
restart (prior to stopping it ran normally). There is plenty of gas
in the tank, battery is full and able to crank the engine vigorously.
So I suspected the ignition system first and did a spark test.

When I unplug the high tension cable from the central connector of the
distributor cap and place it close to ground, then crank the engine, I
get JUST ONE SPARK at the very beginning of the cranking. Does that
make sense? Shouldn't it keep sparking while I crank the engine?

Any ideas as to what the problem could be?

Thanks,
Wolfgang

 

Hi -

Try checking the "secondary" battery connection on the positive terminal for
corrosion. On my '86 240dl, this same thing happened. It turns out that
there are two connections to the positive terminal on the battery - one
primary and one that goes to the fuel pump.

- Stu

 

Do you mean the second red wire coming off the positive battery
terminal? That looks just fine. Is there another way of testing the
fuel flow? Perhaps taking some hose off and cranking the engine, then
seeing if any gas flows or not? Does anybody have a recommendation
for some procedure like this?

But then, how would an inoperative fuel pump explain that there is
JUST ONE SPARK at the very beginning of cranking the engine.
Shouldn't there be a series of sparks as the engine keeps cranking?

Thanks for the information and your help.

Wolfgang

 

Wolfgang,

I had a '90 960 Turbo which just died and cranking the engine did not
produce any continuous spark sequence.

The roadside assistance recovery that I called out checked various
components and what I learned was that a crankshaft motion sensor has
to signal cranking to a circuit board. Additionally on that car there
is a chip (located in a metal box. in the engine compartment on the
inside wing) which is some form of spark control. There was a lead
which resembled a length of soft floppy co-axial cable which is also
problematic (any cut or nick and it fails).

In essence, even with a relatively old vehicle the simplicity of coil
and distibutor to leads has become more complex with reliance upon
many factors. The failure on mine was due to a cracked circuit board
(crankshaft movement sensor) and it was not an expensive repair.

Liam

 

It should keep sparking while cranking. The most common failure would
be the pickup coil in the distributor, then the wiring harness from that
coil to the switching box.

 

The problem was a broken timing belt. I had visually checked the
timing belt through the gap in the belt cover, and it looked ok. But
it wasn't. I had myself towed to a shop, and the mechanic there found
the problem was the belt.

Thanks to all of you for the responses, all of which made sense, too.

Wolfgang.