Tach problems!!!

[CrownVic92]

I was given a sunpro tach. I installed it tonight with my friend but it's not reading correctly. It's running like a 4cyl instead of an 8 cyl. Theres 4 wires on the tach, green,white,red and black. I don't know if we connected the wires correclty but everything is working in tach it's just indicating 4cyl rpm instead of 8cyl. Any one know what would be the problem.? And yes the tach is switched to 8cyl.

[monterey1962]

Pop the back open. Should be one screw holding the back on. There should be a small selector switch. It's probably set on 4cyl. Just flip it to 8cyl.

[CrownVic92]

I did switch it to 8cyl still not showing correct rpm. I I checked if I put it to 4 to see if rpm would stay the same but it doesnt say same so tach switch working. But not showing 8cyl rpm.

[monterey1962]

Sorry, didn't read the first post well enough.

Wires should be:
Green: tach -- to green wire off of coil
White: illumination
Red: Key on power
Black: ground

[CrownVic92]

ok green wire is connected to a blue and white wire off the coil.

and white and red or on the same wire. Only thing this does is the tach light is always on when I turn on the key.

[gadget73]

If this is a 1992 Vic, don't you have a pair of coil packs? I don't think a tach would hook up the same way on one of those cars as the distributor-based engines.

[CrownVic92]

I don't know much about cars still learning. I think it might be that 2 coils but I do I connect the tach to that?

[Freshmeat]

You need a tach adapter. Roughly $50 for a cheap one on eBay.

[p71towny]

Yup, tach adapter, athough I hear some of the older 4.6's have a wire that might work.