Does the fuel relay have any effect on the tach?

 

Possibly, yes. It has a tach input, which keeps it on when the engine is running.

 

My tach is under reading by about 700rpm right across the rev range (maybe slightly more at the higher end of the scale). I have replaced the coil, replaced the distributor and checked all the wiring including the earth points so do you reckon its possibly the cause or is there anything else thats worth checking first?

 

the tach itself?

 

Anyway to test it? or is the only way to test by using a known working tach?

 

does it go to 0 when off or past the bottom? pull the needle off and stick it on further up! is it mk 3 or 4?

 

just been thinking some more about this.... your fuel relay should not effect this as it is on the same cicuit as the coil (green wire) so in theory .....if it affected the reading to the tac it would affect the reading coil and make the car run slower! and we all know that would never happen!