In article ,
The Other Mike wrote:
However, a dwell meter still has its uses on a modern car. All coils -
even multiple ones - will still give a dwell reading pretty similar to
points ignition. A dwell meter will also give a reading from (some)
injectors, as it measures the mark space ratio.

You might struggle to get a signal for a dwell reading from a coil on
plug system without a break out adaptor, sourciing the connectors for
both genders could be a problem too.

You can generally probe the back of the connector.

Plus the question is what you'd do with the reading when the dwell isn't
even specified by the manufacturer and probably won't have been for
anything since the '59 Mini went points free sometime in the 1990's

You're not looking for an exact figure since it can't be adjusted anyway.
Just something in the ballpark for fault finding.

Anyone with any sense at wanting semi-reliable transport would have
fitted contactless electronic ignition to their 'classic' at least two
or three decades ago. Perhaps they prefer to **** about under their
cars rather than driving them. Other than washing and waxing every bit
of maintenance on our classics is done over less than two days per year
per vehicle , that's all maintenance, laying up for the winter, getting
the MOT and recommissioning. They start on the button every time and
touch wood they have never failed at the roadside.

You'll be saying a contact less system can't fail? They can and do. And
being able to fault find that can be useful.

Not sure about more recent kit (only seen throttle angle percentage on
my generic scanner) but some pre-OBD diagnostic kit could display the
injection pulse on time it was actually commanding. But while you
could measure the actual the actual pulse at the injector it was still
no guarantee the injector actually opened and metered fuel, only
removing the injectors and seeing the spray pattern and measuring the
fuel dispensed could eliminate injector problems.

You can use a noid light, neon, or even a LED to see the injector firing
at low revs as they will flash. A dwell meter, however, will work at any
revs. Unlike the lamps which will appear to be on all the time at higher
revs.

Of course a 'scope is far more use for all of that. But is even more
difficult to learn than a DVM.

The snag with a lot of diagnostics is they can tell you what the ECU is
trying to do, but not necessarily if that function is being carried out
properly.

--
*I must always remember that I'm unique, just like everyone else. *

Dave Plowman London SW
To e-mail, change noise into sound.