Classic cars forum & vehicle restoration.

[Phil Lincoln]

I thought I would buy a dwell meter to make sure the distributor on my P4 95 was doing what it should and would show up any wear.
I purchased one from Mapins , read the instructions which said if you connect it the wrong way you will just get a negative reading.
Connected it to the car and got crazy readings .Tried it on a 12v battery and got crazy readings again.
Contacted the supplier who willingly changed it.
Tried the second one and exactly the same.
My Rover is POSITIVE earth , and the LT wire from the distributor is connected to the + terminal on the coil.
Any of you boffins out there any ideas.

Regards to all , Phil.

[Phil - Nottingham]

Some work some dont and some work in reverse ie for a 6 cylinder deduct the reading from 60 (90 for a 4 and 45 for an


The connections may vary too. I have 2 digital ones that just do not work on + earth (swap battery leads & coil to set! - make all other accessories like radios and clocks have fuses removed) an analogue one that reads correct with connexions reversed and one that reads in reverse - this is antiquated Gunsens meter triangular shape that was in a job lot of bits I bought for £2 at the E Kirby P4 ralley 2 years ago - very easy to use
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Rover P2
Rover P4
Rover P5 & P5B
Land Rover S2 & S3
Morris Mini Traveller Mk2

[ukdave2002]

I bought an automotive meter from Maplin that had a Dwell setting, its very accurate, did a comparison with my Crypton unit which you can see in the link below, a great buy (think it was on offer at less than £20) which I use all the time.

Checking the dwell with a meter is far more accurate than setting the dwell by adjusting points with feeler gauges. If your reading is not stable it could indicate a worn distributor shaft.

Dave

http://www.oldclassiccar.co.uk/forum/phpbb/phpBB2/viewtopic.php?t=3361

[Phil Lincoln]

Hi Dave ,I take it you are on NEGATIVE earth.Ive tried two of these meters only to be told ,after much prompting , that they are not suitable for positive earth.
Regards Phil.

[ukdave2002]

Hi Phil

I have used mine for both = & -ve earth,

Sometimes what you can find with electronic dwell meters is that you are reading the idle period rather than the dwell, which is caused by the way that the circurity triggers, ie its looking for a rising edge on the waveform and ends up being triggered when the points open , swaping the leads round can fix this or you can simply subtract (for a 4 cylinder) from 90 degrees.

Or you could pick up a Crypton Tuner off Ebay, there are plenty around and the are as cheap as chips, all have dwell meters on and a host of other stuff, the one I use now was £25 !!

Hope this helps Dave

[Phil Lincoln]

Hi Dave ,this is an image of the Maplin meter coupled to my P4.The readings are the same whichever way round I located the leads.
I returned it and they willingly refunded my momey.
I guess I shall have to resort to the old feeler guages for now.
Regards to all Phil.