Automotive multimeters

Didn't the need for dwell angle go out in 1980s with the death of the Cortina, Capri, Chevette et al?

Can be useful for checking injectors. And regardless of the trigger you still have dwell - so might be useful for fault finding.

However, I think Gunson's stuff overpriced for what it is.

I have at least 4 vehicles that benefit from dwell angle being correctly set, and saw another on my way in to work this morning. HINT: They're not all dead, so there's still a need.

I don't know what dwell is, so either my car doesn't have it or if it does, it's beyond my capabilities. Either way, it's nothing for me to worry about. What is dwell btw?

It seems the yellow meter only does DC, which for automotive use only is fine but the red meter does AC so you could use it for other purposes away from the car.

I wanted one with memory hold. I read an old post here about measuring the battery voltage when you start the car. The yellow meter does not do this, so that rules that out. I downloaded the manual for the red meter but it says -in broken English - that when you press hold it simply "holds" what is on the display. That doesn't sound right either; what if I don't press hold when the voltage is at its lowest?

Is there a meter that records maximum and minimum levels? I have an old Maplin white gold meter which records maximum values but not minimum ones.

Fred gurgled happily, sounding much like they were saying:

On a car with points & condenser (if you remember those...), it's a figure you really ought to bear in mind when adjusting the points gap and timing angle.

It's the angle of distributor rotation during which the points are closed.

It's the angle that the coil soaks at 12V before firing. Modern EFi will change this from as little as 30° at idle to 200+° at full load. Only way to find this spec is to hack the ECU and read the rom maps.

It's the angle of engine rotation that the injectors are open. Not a lot at warm idle, lot more at cold idle and longer than the valves are open ~270° at full load. Again a hack the ECU job to work it out.

Though just getting an dwell reading shows they are functioning and getting that dwell to vary shows the ECU is responding to inputs like throttle, rpm, airflow, temp.

Fred expressed precisely :

It is a percentage - the time the points are open versus closed. A more accurate way to set the points than using feeler gauges.

The hold is no use for that, you need one which records min/max. Yes you can get them, I have a Fluke which does it.

Or it's normally available via a fault code reader.

Well if you find an 867 on Ebay then it's still the best car multimeter I've used. Otherwise

Yes- my Fluke does that. But may be too expensive for occasional use. Have a look on Ebay - quite a large selection there. And you'll likely get good value. I'd get one which can measure temperature too. And one which can measure at least 10 amps - anything less will be pretty useless for car stuff.

Aye. And the more cylinders you have, the smaller the percentage, so the more critical it becomes.

In message , Fred writes

It does. Anything that uses an inductive ignition system will have dwell time.

Or not relevant because it's controlled by the ECU and non adjustable.

Probably not.

Charge time for the coil, it's an archaic term that goes back to points ignition, IIRC it's the amount of time the points are closed, dwelling in the low spot of the cam that drives them before it opens them. It usually refers to ignition coils but the same measurement can be applied to any inductor hence the comments about checking injectors with a dwell meter.

Ideally get a fast data logger/sampler or storage oscilloscope. Very much overkill though. Get an analogue meter and have someone crank the car while you watch the needle.

That's the voltage you get on the screen. It's pretty much the same for most meters but some do have min/max functions.

Yes, there are meters that will do this.

ODBII interface then you don't need a dwell meter.

It depends on what you want to know.

Describing it as an archaic term is wrong. It's still in use as coils are still used and dwell still applies to them.

A dwell meter measures the mark space ratio so can be useful for anything that switches quickly. Inductor or not. It will give a reading on a piezo injector.

In message , "Dave Plowman (News)" writes

Not really, it harks back to the beginning of the Kettering ignition systems so the term is archaic, it doesn't mean it's no longer applicable though ;-)

Of course.

I know.

I agree a dwell meter can be useful but it's less useful than it once was, an LED and current limit resistor across the injector is much cheaper with the advantage that you can see the peak/hold current changing. It's a *lot* more difficult to damage by dropping on the floor and is extremely cheap to replace if you do manage to break it or, speaking as the new owner of four 'road kill' LED inspection lamps, lose it.

It will also work with cam/crank position sensors.

I haven't seen or played with piezo injectors yet but I guess it'd only be the voltage that's (painfully) different.