Rod being connected up to the life support machine, for a full ignition system check up.
It might be old but this still works! (sounds like me)
Rod gets a tune up on a 1972 engine tester.
This is a wonderful bit of old kit, now it would all be on a lap top computer and not weigh half a house!
Still it was fun remembering how too read all those dials and even how to connect it up to the engine. The main thing it has made an improvement to ROD's running.
I have been asked what the engine tester was showing, well the r.p.m. was 900 a bit on the high side, the exhaust gas was shown as being 5%, slightly rich, the timing was spot on at T.D.C but the dwell angle (this is the time in degree's of rotation that the points dwell in contact with each other) was out of adjustment.
The only time you can set points accurately with feeler gauges is when they are new, once used the surfaces are pitted and uneven, feeler gauges are then no use. If you can measure with a meter the contact time you can adjust any set of points.
The dwell angle is very important, you need the points to remain in contact with each other as long as you can to "charge up " the coil, you also need them to open quickly and cleanly to provide one high intensity spark as the coil discharges. If the dwell angle is to high, the points are remaining closed too long and vise versa, as each degree that the points are out, affect the timing also by a degree.
When using this engine tester you can see on the oscilloscope the the primary ignition line, and you can see if the timing on each cylinder is the same! It not on ROD, due to a worn distributor bush, the four lobed cam is NOT running central, so number one cylinder is set up and firing correctly but number 4 cylinder is in fact approx 2 degrees retarded! A new bush or a new distributor is required.
Checking the secondary firing line on the scope showed that the coil was round the wrong way. This was due to me changing the vehicle to negative earth. Why is this important? Well its due to electron flow, we know electrons flow in an electrical circuit, well electrons flow easier from a hot surface to a cooler one, like steam coming off from boiling water, so the hottest part of a plug is the tip, so it helps if the electrons flow with the "heat radiating" from the hottest tip to the very slightly cooler side electrode.
The other thing the scope showed me was that one of the H.T. leads/ sparking plug cap was high resistance, this was giving a weaker spark on that plug.
You would be unable to see this with the naked eye, the engine tester gave early warning of the plug cap braking down.
Still plenty of things to do before the M.O.T. and plenty of painting to be done at a later stage maybe by me or the new owner, I need to sell ROD to pay off the credit card bills and give me some time to work on some of the other fleet, any offers?
