7 replies to this topic

[Alburglar]

Arghhh!
Something keeps buggering up the optical eye on the electronic ignition on my 1380 road rocket, it's happened twice and the coil has gone 'constant open' once too!
Swiftune thought that I might have a positive earth, but i have checked and i havn't. What could it be?

For the time being I am re-verting back to normal point's ignition and have put in a good condition a+ distributer and points, condenser. how do I set up a new dizzy from scratch?
I have put it in, what next?

Any help on either issues will be much appreciated.

[Dan]

Use new points, condenser and rotor arm even if it isn't very old just in case, set the points properly, then you need to do static timing. Turn the engine by hand until #1 is coming up to TDC on it's compression stroke (that is to say when the valves on 1 are both closed and the inlet is just opening on #4). Keep turning the engine to set the timing mark on the pulley to correspond to the correct tooth on the timing scale on the front cover. 8 degrees BTDC is a good static point to start with (not knowing exactly which engine you have), and that is the third spike down the scale. If you don't have timing marks/scale at the pulley you can use the ones on the flywheel, if you have a lightened flywheel too then you may have to guess a little bit. The crank must remain in this position until you are finished.
Now undo the dizzy clamp and you will see the rotor arm pointing at the position for #1. This should be the top right hand corner of the dizzy, if it isn't then pull it out, pull the drive gear and turn the gear round by the correct amount and get it in the right place. With the rotor pointing to the right part of the dizzy, slowly turn the dizzy body back and forth a little until it finds a position where the points have just opened. But only just. Re-tighten the clamp and fit the cap and leads, the firing order is 1-3-4-2 placed anti clockwise around the cap from where the rotor arm was pointing for #1.
The engine should now start and run fine, but it won't be very efficient or healthy so you will need to do dynamic timing straight away in the usual manner.

If this is your GRP car you need an earth loom by the sound of it. I did edit up a more detailed description of an earth loom with pictures, and what I think the problem is but then the damn board glitched out for a second and lost it all. No time to redo it now, I'll get back to you if you want to know more.

Edited by Dan, 23 January 2005 - 10:12 AM.

[Alburglar]

many thanks dan. Yes it is my grp car.
If you get time to explain the earth loom with your pics. It would really be of help to me. You could e-mail it to me with the pics. [email protected]

[bluebottle]

have you gone through the fault diagnosis instructions that came with the lumenition?.....i found them to be pretty good, and led to me solving the only problem i've had with it.

my power module is earthed to the engine, which is well earthed to the subframe (my car is also fibreglass).

[Dan]

Right, okay then lets try again.

Earth loom.
(there now follows some boring technical junk that you probably won't want to know)

The problem with electrical systems in GRP cars is one of floating earths. It's all to do with the earth return being the steel substusture of the shell, and this being buried inside loads of GRP. It isn't certain that the steel parts have the same cross section all the way thoughout the shell, and some of the parts can become isolated from each other as part of the bonding process when the resin starts to flow through the mould. What you basically end up with is an unpredictable internal resistance of the shell from one earth point to another. So it might have little or no resistance from the headlamp earth point to the battery say, but a much higher resistance from the engine earth to the battery. The difference won't be much and it would be hard to measure or control in manufacture but it matters. What this means is that as the internal resistance of the battery changes with use the earth value changes. Basically the shell stops being just a conductor and becomes a component in the circuit itself which everything else is in series with. The value of the earth points could rise from 0v (negative terminal nominal voltage) to 2v, say.
So effectively the cars electrical system has been dropped to 10v. You will get dim lights, weaker ignition, slower starting and stuff. But also something else will happen. Effectively the supply voltage is changing continuously and semi conductors (such as parts of your optronic ignition) don't like that at all.
This shouldn't happen to stuff on the engine because obviously the alternator is earthed directly to the block, but it can do if something is also amiss with the alternator, or if you are running a lot of load (like in winter) and the alternator isn't supplying all the car needs so it draws from the battery.

End of technical section.

So, basically lots of GRP cars have an earth loom to get round this problem. In Japan you can buy earth looms for Mini's off the shelf as GRP silhouette racers are very popular over there. It consists of a load of extra wires basically. They are usually all made of braid (like your engine earth strap) and connect the negative battery terminal directly to all the main earth points of the car (cars tend to be made with centralised earthing points as it is faster on the line to screw lots of tags on in the same place than to earth each item directly). Late Mini's should have 3 main earths, but you might also find some others on your car which are a good idea to tie in.

Now I'm not saying this is definitely your problem, but you could find out by temporarily and safely running just one thick cable from the engine earth directly to the battery negative as a test to see if it works. Use an old set of jump leads and get a battery clamp and a decent lug for the other end and give it a go. If it works then build a full on earth harness.

Earthing directly to the subframe won't change anything, unless your subframe is properly connected to the battery itself of course.

Edited by Dan, 01 February 2005 - 07:26 PM.

[Alburglar]

Excellent. Thanks you two.
Without knowing it, that is exactly what I've started doing. I put a massive 4 guage wire (about 2cm thick) straight from battery negative to the flywheel casing. Then a braided strap to a metal plate under master cylinders and back into the car to the base of my solenoid (which is located under my dash). In order to provide an earth point for other bits and pieces.

I will put a thicker braid strap from engine to subframe too.

[bluebottle]

my jem uses the subframes as a kind of chassis to earth to.
the subframes are joined by a large battery cable, and then just about all the other earths (including the negative on the battery)are joined to one of the subframes.
things like the instuments have their own bunch of earths, which are made into a small loom, which then picks up on the front subby.

i had the car professionally rewired about 5 years ago, and it now has a weatherproof blade type fuse box, transistorised flasher units, a couple of extra main car fuses, and a battery cut off switch.....was the best £400 i ever spent!......everything works all the time!

[Alburglar]

have ordered a ballast resistor and dlb 111 coil from lumenition too.