speco tacho trouble

[n8dzy]

morning all,hoping someone can help me out with this one.Have fitted a procomp HEI dizzy with coil mounted in top,to my blue 253.I have now fitted a 2in speco tacho with all wires soldered into correct spot,the tacho seems to work fine during idle but as soon as you take for a drive and get above 2000 rpm,it starts to spaz out and the needle starts to flick back and forth.I would also assume that the idle speed is out just by listening.Just to confirm the cylinder selecter is in the 8 option.cheers

[Jonno]

its connected to negitive on the coil yes?

[n8dzy]

yeah man,on the dizzy cap there is two terminals.One for tacho and one for 12v constant power,so as far as i know its all connected properly.One thing i was wondering though,if the timing was too far advanced would the tacho spaz out like that?The car does run on sometimes but again i think the timing is right.Thanks for your reply mate hopefully you can help me.

[ari666]

its not a V8 tach on a 6 or vice versa?

[Hangman]

Not saying it's causing your issue, but I wouldn't use procrap anything if you paid me. Too many horror stories...

[n8dzy]

thanks for the reply fellas,as for the tacho it has a selector switch with 4,6,8 and ive got it on the 8 so i think thats right.As for the procomp gear ive heard they make some definate rubbish,but a few good things also,so fingers crossed ey!

[ari666]

their dizzy'z are not that bad. their coils are crap. may as well throw that bit in the bin and get a hec716 bosch.

[n8dzy]

thanks for the advice mate,any ideas on how i can get this tacho working?Cause i am having trouble trying to get the idle speed set right without it.
cheers.N8

[ari666]

well, if you have the correct wire connected for the tach, then i am a bit stumped really. maybe just prentend you are starting from scratch and check each wire again. earth is the pulse signal. it will be the same wire that triggers the coil. then the guage itself will need 12V (ignition on) and illumination. with the switch set on 8, there really shouldnt be a problem.

soz i can be more help.

[n8dzy]

yeah i think your right, i will have to start over.Now when it comes to the earth wire off the tacho ive just got that running to a bolt in the firewall,is that maybe my problem if so where should i earth it to?The instruction sheet they gave me with the tacho was as good as a c**k flavoured lolly pop,so that didnt help alot for a first timer.Hey man cheers for your reply hopefully ican get this bugger sorted soon.

[mr j-man]

yeah i think your right, i will have to start over.Now when it comes to the earth wire off the tacho ive just got that running to a bolt in the firewall,is that maybe my problem if so where should i earth it to?The instruction sheet they gave me with the tacho was as good as a c**k flavoured lolly pop,so that didnt help alot for a first timer.Hey man cheers for your reply hopefully ican get this bugger sorted soon.

haha "#### flavoured lolly pop" classic i cant say ive ever heard of that one b4.

[ari666]

.Now when it comes to the earth wire off the tacho ive just got that running to a bolt in the firewall,is that maybe my problem

soz i never noticed this post.

yes, yes that will be your problem. without a doubt. the earth wire is just a wire going from the coil to the dizzy, the dizzy pulses each time it passes each point on the rotor and the pulse triggers a flash from the coil. if you splice into that wire, then each time it pulses itll tell the tacho also that it haspassed (x) amount of rotations.

the only wires from the car to the coil should be from ingition 'on' (+) and tacho (-). the two wires from the dizzy go on the + and - of the coil.

[n8dzy]

cheers for the info mate,im finally starting to see the light.Just to confirm though,on my dizzy the coil is mounted in the cap and it just has one terminal which i have the green wire from the tacho.So do you think i should splice the ground wire into that?

[ari666]

man a pic would be really helpful, i have nfi

[n8dzy]

good idea,i will try and upload one tommorow,thanks mate,y