Dizzy 3 Pin Wiring Plug

[mos 1]

as per my earlier post i having been trying to track down a fault with the rev counter behaving erratically above 3000rpm (needle bouncing around not unlike when the speedo cable is worn) but only intermittently.

 

had my head under the bonnet last night when i noticed something strange with the dizzy wiring the wiring plug from the dizzy to the main loom has been cut out and only 2 of the 3 wires had been hard wired into the car main loom. i have tried replacing the coil and ignition module and am about to try a spare dizzy

but having now seen the tampered with dizzy wiring its got me thinking that this is where the problem may be.

but what i dont know is if the dizzy has anything what so ever to do with the rev counter, if it doesnt i would be barking up the wrong tree here.

does anyone know if the dizzy is connects to the rev counter in some capacity?

and what do the three wires to the dizzy actually do? should the third wire actually be connected on a twin carb install or can you only use two i.e the third wire is something to do with fuel injection etc which has now been binned?

 

help!

[ada205 2]

but what i dont know is if the dizzy has anything what so ever to do with the rev counter, if it doesnt i would be barking up the wrong tree here.

does anyone know if the dizzy is connects to the rev counter in some capacity?

Yes, the dizzy is the very start of the rev counter signal. If your distributor dies, your rev counter dies! The wire you mention is also sheilded to stop cross interference, so a break could make your symptoms worse the higher the revs climb.

 

Definately change the lead, theres a very good chance it's the cause of your problem. If you aint got a spare lead, I've got one you can have for free if i can find it!

 

Good luck.

Edited July 21, 2006 by ada205

[mos 1]

thanks ada205 but i have just found one in the garage

 

i just looked up the wiring to the dizzy in a haynes manual

it shows all three wires going from the dizzy to the coil

they are numbered 141,140,139 in the haynes manual someone must know what each one does?

this fault is actually getting worse and although its not effecting the running of the car it is driving me mad

 

help!!!

[pug_ham 245 3 Cars]

They go to the ignition module not the coil & are the field windings for the distributor that create the feed to the rev counter.

 

Wurzel has recently had problems on his project car with this lead, when it fails completely the car simply won't run which I believe is currently the problem on Karlos72's car.

 

Graham.

[mos 1]

thanks

 

i tookthe lead apart and in deed there are only "two active" wires, the third wire is an earthing strap/anti interference wire of some descripton, this was disconnected from the part of the wire coming from the ignition module and the whole lot are protected by sheilding.

patched this up best i could and tried it again, fault is still there.

 

i then tried a spare 1.9 dizzy and guess what the fault seems to have disappeared!

i am going to leave this dizzy on for a few days to ensure the fault does not reappear as it is usually intermittent.

 

i am quite gutted about this as last year i bought the dizzy that appears to be faullty from skip brown for circa £200 with the VAT, then i sent it to richard longman to alter the advance curve to give 20degrees BTDC at idle to improve performance with my carbs and modified head and cam.

i am wonderig if the fault has actually been there all along or at least since richard longman modified it and i only notice it now as it has become more and more prominent.

not fully understanding the inner mechanics of a dizzy i do not know if something would have been distrubed when altering the advance curve?!

 

anyone shed any light on this please, i know what a dizzy does and the theory behind how it works but from a practical stand point i have no idea to the internal mechanics

 

thanks

 

mark