AMGBA website home page or AMGBA Photo Gallery or AMGBA Club Blog

Join or renew for 3 years and receive a free t-shirt
or tech sections on USB flash drive /emailed/CD or past Octagon issues on USB flash drive/emailed/CD
see details in the join the club section at!

Tach Problems

Started by september2020, August 09, 2020, 02:37:27 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.


We acquired a 1970 MGB from my son as a 50th wedding gift. He knew we liked 2 seater rag tops because we owned a Austin Healey and a 124 Fiat Spider before we had kids.

I can go on about all the things that are wrong, but on start up when you first turn the key and the fuel pump starts the tach goes bananas rocking from 0 to 6000 rpm. Is this normal or is there a problem with the tach or the pump?

I'm also curious as to where you (John Twist) were in Vietnam while in the service.  I was in Natrang 43 Meical Hospital.

The only reason why I ask is because I have watched so many of your videos and feel connected.

Jim Young


It is normal for the fuel pump to tick for ten seconds or so when you switch on the ignition, but then it should reduce to a click every ten seconds or so.  That is, if it's a factory SU fuel pump.

The tach swinging wildly indicates a fault in the wiring and/or a faulty tach.  The fuel pump circuit is common with the tach circuit, and it's certainly possible for an incorrect connection to have been made which would cause this. 

My Vietnam service began 17 June 1969.  My first assignment was to G-3 Artillery at USARV headquarters at Long Binh.  This five man office (LTC, MAJ, CPT, two E4s) kept track of the radar units (MPQ4s etc) and reported "accidents and incidents" when we shelled our own men.  By October I requested a reassignment to a fire support base.  When I arrived at the 25th Inf Div for transport to the FSB, the G3 called me in and asked me to work in the HQ there – Cu Chi. 

I spent the remainder of my deployment working in the TOC, but flew enough hours with the chemical corps to get my combat air hours logged for an Air Medal.  The entire time I was a clerk, chairborne, ending as an E5 71B.  Two R&Rs in Taipei.  I ETSed 18 June 1970 as I had less than two months of active service remaining.  I was RA on a two year enlistment.  A good friend was editor of our college yearbook and asked for a picture of me to include (even though I didn't graduate) in the publication.  I had a friend shoot a whole roll (36) of B&W to get a Rambo shot.  This was the one I sent -- from bunker guard duty.  In a more detailed shot you can see the starch lines in my fatigues.  I had a great time in Vietnam, but I know most experiences were not the same as mine.  At the time of picture I'd been an MG owner for about a year.

John H Twist
University Motors Online
100 East Beltline Avenue SE
Grand Rapids MI 49506-2410
Cell  616 307 6737
John H Twist
University Motors Online
100 East Beltline Avenue SE
Grand Rapids, MI  49506


If you have found my technical advice helpful, please consider making a contribution to help defray my online expenses.  Go to my website and click the PayPal button:

   back to AMGBA website home page or AMGBA Photo Gallery or AMGBA Club Blog