Coil and rev counter Issues

[sean]

Last week when I went to fill up my bus after standing for 2 or 3 days it suddenly had developed a peculiar miss on when trying to rev the engine up. First idea was to check out the coil and it was to blame.

I replaced it temporarily with one of those electronic ignition Silver Bosch units but what is the purpose of this hole in the picture of my old coil? Can it be refilled or something in that line?I should mention that oil was leaking out of my coil that I noticed when taking it out. This coil as far as I am aware the correct one for the type 4 electronic ignition.





The second question is my rev counter no longer works with the new coil. It just jumps around and at short intervals shows the correct reading. It is the VDO unit that is found in the SP beetle’s. It is also wired strangely with the sender wire to the positive side of the coil, as far as I understand it should be the negative but this doesn’t work with this unit. Any idea’s why this rev counter doesn’t like a new variety coil but works 100% with an old one?

Many Thanks

[buggyfan]

in reply to your rev counter wired strange comment
heres the sp VDO revcounter wiring courtesy of Tom Bishop

http://www.aircooledvwsa.co.za/viewtopi ... ng#p116277

[Dawie]

The SP rev counter basically senses current in stead of voltage. It is connected in series with the "ignition on" 12V feed to the coil. (The terminal marked "15").
Unlike the voltage-sensing type rev counter, which connects to the points side of coil (marked "1").

Ideally, only the coil must draw current through the revcounter. Idle cutoff valves, choke heaters, relays,etc, should preferably have their own 12V feed from the fusebox, so that they do not draw their current through the rev counter and possibly upset the current sensing.

An interference suppressor or radio connected to the wrong place will stop the rev counter from working, or make it act erratic. (Suppressing the "sensing spike"). None of these should be on the sense side of rev counter. Strange connections sometimes happen under the dark and sometimes difficult to reach dashboard of a car.

Some other makes of older rev counter (some Smiths, etc), also used current sensing like the SP rev counter.

[Muderick]

Either this is a coincidence or it must be related for sure.

Sean, I had a similar experience on my way back from George on Monday afternoon. I have an Equus type rev counter installed in my bays dash cluster. After changing my distributor from the original one (due to problematic Bosch points), I fitted my 009 with Ignitor...no points or condensor. Problem solved, but just before fitting the rev counter' wire to the coil again, my mechanic advised that the rev counter might not work, due to the current / voltage difference as explained by Davie above. We fitted the wire, I started up, and she worked a treat! Score!.. I thought.

On Monday just after Riviersonderend, the tacho needle starting jumping up and down erratically, and I thought the wire was loose. When we stopped, I checked, but it was on tightly. This morning, 5 minutes after starting up the bus, the engine cut out, not wanting to start at all. She only swung, but no starting at all.

I checked all the terminals on my coil, and found no issues. I then decided to pull the wire coming from the Rev counter, off the coil. I swung the engine, and she fired up as if nothing happened before.

After reading Sean's post, I am wondering if there is any relation to it, or if my experience is something different? Will the fitting of my Bosch high voltage coil (silver body with the blue Bosch sticker) alleviate this problem.

Any help would be appreciated here guys??

Muds

[sean]

I checked mine again and definitely seems to be a coil compatibility issue. The rev counter works 100% with the old faulty coil but not with the new one. I cant find much on Google either relating to this.

I am rather just going to get hold of another original.