tachometer problem

[xcashewx]

the tach in my 230 works fine when accelerating but when you hit about 60mph at about 3200rpm the tach no longer moves but the engine and speed is clearly getting faster when i press the pedal down. i checked the connections and they look good... any ideas??

[al_lieffring]

Hi

I think that the forum members are not replying to your post because there is not enough information provided to make a good diagnoses.
First let me ask fore some more specific information;
When you accelerate in second or third gear will the tachometer (engine speed) go up over 3300rpm.
Does the speedometer work smoothly at all other speeds or does it jump up and down when the vehicle is at a constant speed?
have you checked the dash tachometer against an eleectronic engine tester's readings.
Have you checked the speedometer against the speed reading of a GPS unit?

My gut reaction is that your car is in fact not accelerating above 60mph and that when you are pushing down the accelerator, the engine is just making more noise, not going faster. There are several fuel and /or ignition related problems that show up at the speed that you are mentioning.

I have seen tachometers that from lack of use wont read above a certain point, but it seems unlikely that both the speedo and tach would stop working at the same point, they are two completely seperate mechanically operated systems.

See if you can gather some more information for us and we will try to help you work through this.

Best of luck

Al

[xcashewx]

it does go above 3300 inthe other gears all the way to redline
the speedmometere jumps around from 0-20 mph

[glenn]

A little lube in the cable, needle, odometer??

[al_lieffring]

it does go above 3300 inthe other gears all the way to redline
the speedmometere jumps around from 0-20 mph

if the tach goes over 3200 rpm in the lower gears that would mean that if it is only showing 3200 in high gear, the motor running out of steam at 3200rpm.
It sounds to me like a tune up issue, a set of burnt up points will cause the motor to hit the wall and not go over 60mph. Replace the points (filing old points iis a waste of time) and the condensor. set the dwell and timing, A plugged up fuel filter could also cause these symptoms. At this point you would have already done half of a tune up, so you might as well plan on adjusting the valves and replacing the spark plugs.

The jumping speedo is a different issue, possibly just a cable needing some lubrication. Worst case, the output shaft nut for the flex disc yoke on the back of the transmission is loose and the speedometer drive gear is sliping inside the tail housing of the transmission.