Welcome to our Site for MG, Triumph and Austin-Healey Car Information.


MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - moss solid state fuel sending unit

I just installed a moss solid state fuel sending unit.My old (5 yrs) unit was leaking at the wire connection. The new unit has 3 spade connections. One is marked with a blue dot and also had a plastic cover over it. I connected the wire to that terminal and now my guage doesn't seem to work at all. The old unit worked, all though it read high by about a quarter.I also have a new voltage stabilizer but have not installed that yet. Is this the right connection? I tried the other connectors but didn't seem to make a difference.


B Stone

Ben. The best source for this information would be Moss Motors. They are the ones who sold you the unit, provided whatever instructions they felt you needed to properly hook up the unit, and are the only ones who, if there is a problem, can authorize a replacement unit. Thus, they would be the first people I would contact and request assistance from.

Les Bengtson

Thanks Les. No instructions with the unit. Thought I would get some quick advice from people who are using them in the field.
B Stone

Solid state or printed circuit? What part number? What year car? The printed circuit type is simply a variable resistance same as before, but achieved by sliding a mechanical wiper over circuit pads instead of a winding, so not solid-state as far as I'm concerned.

Connect a known good earth to the wire that goes to the sender - with the ignition on - and see if the gauge moves. If it doesn't then there is a problem back through that wire and the gauge to the instrument voltage stabiliser.

If it does then connect the same wire to the body of the sender somewhere and see if the gauge moves. If it does't then the sender isn't earthing. Originally there was an earth wire on a sender spade going back to a number plate bolt, later on it was expected to earth through it's physical contact with the tank and the tanks physical contact with the body.

If the gauge moves with the wire on the body, but not on any of the spades, then the sender is faulty.
Paul Hunt

If you look closely,the one with the the cover over it has a WL at the side for warning light which isn't needed.
on the opposite side is an I which is for instrument which goes to the gauge.
the middle is the earth.
Ste Brown

David DuBois is one of the resident experts on fuel pumps. I know he has a business fixing older pumps and also converts older units to solid state. He should jump in here shortly.
Bruce Cunha

The three terminal types need an eath wire as well as the signal wire from the gauge. Ignore the terminal with the plastic cover, use just the two uncovered ones.
Paul Walbran

Thanks Paul, I hooked up a temporay ground and the gauge does work like the old unit although not very accurate.I will work on that. Surprised that Moss doesn't include any paper work with this unit. Ste was right the terminals are marked but very hard to see.
B Stone

You're welcome Ben. I remember it had me puzzled when I first saw one :-)
Paul Walbran

Agree you ignore the covered terminal. Mine came with a photocopied connection diagram that proved to be upside down.
V Todman

This thread was discussed between 10/08/2013 and 19/08/2013

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now