Jumping Rev Gauge

[davev 1]

hi. i have just developed a little problem the i hope someone could confirm that its the ignition amp.

 

my car is a mi16 but i am running 8valve dizzy and management , and when accelerating through the revs at around 4500rpm the rev needle starts jumping around(usually jumps to 5000, flickers, then goes to 5500, and then drops back to 5000).

 

the car doesnt seem to missfire or anything like that but i usually back straight off, although yesterday i decided to carry on for a little bit and by time it dropped back to 5000rpm it seemed to go normal again.

 

i suspect the ignition amp as it was only last week that i changed it(new gsf jobbie) and have only noticed this since.

 

could anyone confirm it. or have a reason why my needle would jump around for no apparent reason.

 

thanks.

[welshpug 1,657]

could be anything that causes a lack of spark or a misfire, i.e coil or ignition amp, or the signal from dizzy to ignition amp, or the power supply to it, or its earth even.

[davev 1]

the thing is it doesnt missfire from as far as i can tell.

 

when i went up to just over 500rpm it carried on pulling nice and smooth like it was all normal.

 

my dizzy was refurbed about 2 years ago with new signel wire and the coil was changed sometime before that.

 

on a side note i remember the amp having an extra pin out, the connector was still the same but the last pin(or first what ever way you look at it) had no wire going to it?

[Anthony 1,003]

If the problem only appeared after swapping the ignition amp, I'd replace that first of all with a known good one and see if the problem disappears.

 

When you installed the new ignition amp, did you use some heat transfer paste between the amp and alloy plate?

[davev 1]

yep i used plenty of heat sink.

 

i still have my old one i could possible try. it didnt seem to be faulty but was getting on quite a bit and didnt have any paste on the back.

[timb1046 1]

yep i used plenty of heat sink.

 

i still have my old one i could possible try. it didnt seem to be faulty but was getting on quite a bit and didnt have any paste on the back.

 

 

this is probably the cause of the problem. "If it ain't broke then don't fix it!" if you replaced everything because 'its getting on a bit' then you may as well go and buy a new car!

[davev 1]

i replaced it as i had freshened up the other parts and this was the only part what was left in the ignition system from when i bought it. oddly all the other things failed.lol.

 

also the car has only been back on the road since pugfest and it was meant to be put on before i got it on the road.