Ignition coils HELP , misfire / backfire

[busa paul]

have been having problems with misfire and back fire on a regular basis .
have fitted new plugs ngk 7eixs or something like that ,

have replaced fuel filter was rotten

so now have checked coil packs
and got the following readings

primary
620 ohms
650 "
720 "


secondary

21000 ohms
20000 "
19500 "


can any one please tell me what the readings are supposed to be
or any possable other reason for the misfire / backfire

[peter thomson]

Those figures are not too far off what I measured when I was looking for a fault. Turned out to be the fuel pump in my case.

[bigoxo]

One of my coils cracked and used to arc off a nearby bolt at times, causing a misfire. You could see a tiny white spot where it was arcing from. or get someone to rev it while you watch for the arc....course it could be the fuel pump - like peter said.

[busa paul]

got me some replacement coils all of his measured 580 ohms and 22k
misfire now missing !!! runs better than ever , and noticably better on fuel

so up for grabs 3 used coils (one dying )

[karlous54]

How do you test the secondary side of the the coil packs ? do you need a fairly good meter to do this ?