MGB Tach slow to wake up...why?

[Joe Reed]

I just watched a YouTube video of a very low mileage MGB LE for sale. When the saleslady starts the car the tach stays pegged on zero, and then "wakes up" a few seconds later. My car also does this...and has for the 20 years I've owned it. I don't remember if the '72 Midget I had back in the day did this, but there's a lot I don't remember from the 1970s. The only other MG I've owned was a '79 I sort of inherited but I only drove it once (it ran horribly) before Tony Barnhill came to get it. I never would have noticed if it had this same affliction.

This seems to be very common, but I've never seen an explanation of why this happens. Anyone with enough knowledge of these instruments know why this occurs?

I have no intention of trying to "fix" it. I find it to be sort of an endearing quirk. It's as if the car first says "Wait...let me finish waking up!"....then, a few seconds later tells me "OK, let's go!"

 

[pdplot]

My TR6 does the same thing. Has done it for over 20 years. A rap of the knuckles and the tach comes to life.

 

[NutmegCT]

If I recall, on my MGTD and my MGB, same thing happened The grease was old and "sludgy". Removed the old stuff, replaced with new grease, and all was well.
Tom M.

 

[DrEntropy]

I put up with that in the Elan for a while, got tired of tapping the thing and removed it to renew the lubricant. All better now.

 

[Svcmangler]

what exactly are you lubricating?

 

[NutmegCT]

what exactly are you lubricating?

Some hints on tach/speedo maintenance:

https://mgaguru.com/mgtech/dash/st109.htm

Tom M.

 

[Joe Reed]

I can tap mine to get it going, but it starts up without that after a few seconds....or if I rev the engine a bit. Not something I want to remove the speedo to fix!