S4 (Federal) Convertible Ignition Problems

[richardcox_lotus]

The box looks like a voltage stabiliser to balance the voltage going to the fuel gauge.

Regards
Richard

[sprintsoft]

Hi Rick,

given that the original problem was that the engine died at the same time as the tach I think you are on the right track i.e. isolate the tach by using a direct to coil 12v feed. You now need to confirm that fix works by driving it.

Let's assume that it drives OK, then the white wires in and out of the tach are up next, I would replace both of these temporarily to make sure you have 100% connectivity and to see if it fixes the tach. If it does then the white wires are intermittently broken somewhere.

I would test the voltage at the coil +ve terminal with the ignition on, to check if you see the same voltage from the original white wire feed compared to your temporary parallel wire. (Edit: test them individually, don't have them both connected to the coil at the same time)

It is also possible you have an intermittent connection within the ignition switch.

The RVI tach can work with Pertronix without modification but it is normally recommended to convert to RVC to get it reliable - however this is not your issue here, even if an RVI tach doesn't work correctly it will still feed the coil.

As Richard pointed out your pic shows the voltage stabiliser attached to the back of the dash. It may or may not be working, but it will not influence your ignition feed. If you want to test it, just apply a 12v feed into the 'B' terminal and make sure the case is earthed, then you should see a steady 10v from the 'I' terminal, it its unsteady or lower than 10v just replace it.

It's good you have decided to trace these bugs through, Phil is a great help I'm sure, and removing all those dead wires must be very satisfying!

Iain

[gjz30075]

Rick, re: #4; that is your fuel guage regulator. 12v in and 10v out. Should have nothing to do with
your current (no pun intended) problem.

[collins_dan]

The tach does not need to be converted to rvc to run electronic ignition if you power it separately from the coil. I ran a red wire from the fuse box and have never had a problem. Dan

[hubrick]

Hello All,
Wow, great progress. Just replied to my other post about all the other electrical things that I'm working through and sorting out. Yesterday I got back to the ignition problem again. Progress there too.

I discovered that the wiring to the anti-theft switch has been disconnected by the PO. I was fooled a week or two ago when I had test light power to the switch. It wasn't until fixing grounds that I realized that the ground wire to that switch was the source of power. Once I had the dash pulled back as far as it will go with the steering column still in the car and the tach out of the dash, I had no continuity from either of the white wires at the back of the tach to the anti-theft switch, and after that I found the disconnected wire. I can live without it.

The wire from the tach to the coil had a questionable looking bullet connector at the tach and two splices in it before disappearing into the harness to the engine compartment. I just replaced that section of wire with a new one, new bullet, and a single soldered splice, so now I have power from the ignition switch through the tach to the coil. I hope that solves the intermittent ignition failure problem. I have the spare wire from the ignition switch directly to the coil just in case.

So I'm getting close to driving again. Only has taken a few weeks, but made much easier thanks to the help from all of you. I appreciate it.

Cheers,
Rick
70 S4 (Federal) 45/0030K

[hubrick]

Hello All,

Here's a wrap up to my ignition trouble which is now hopefully fixed. I discovered that the anti-theft switch had already been disconnected by the PO, believe it or not, the intermittent power I was finding there was backfeeding through the ground wire. Talk about causing some confusion.

There were two splices in the wire from the tach to the harness going to the engine compartment where the white wire went to the coil. I decided to replace that wire with a single soldered splice.

So today, I put everything back together, and have everything working but the headlight vacuum (waiting on parts) and the horn (waiting on wires from Dick Britton's old harness). Quite an accomplishment - yes it took me 4 weeks, but it's great to have it all working again.

Couldn't have done it without the help from this list - particularly Phil and Dick. Thanks very much.

So today was maiden voyage with almost everything working again. I'm keeping my fingers crossed that I found and fixed the intermittent ignition wire problem, but as a back up, I have a spare wire the PO ran from the ignition switch directly to the coil area. If mine fix lets me down, I can switch to that one, and get back home again.

Hope I have many miles and many smiles ahead of me with my little Elan.

Cheers,
Rick
70 S4 Federal (45/0030K)

[pharriso]

Congrats, enjoy your runs!