MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

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 - testing a coil & SU fuel pump coil

Is there a correct way to test these on a bench? Russ
RAH Russ

Ignition coil and SU pump? The question is a little unclear.

If yes you need to set the coil up with a connection to a battery with a condenser in the return path. Connect the coil HT to a spare plug that has it's body also connected to the return on the battery. By shorting and unshorting the condenser you should get a fat spark at the plug when you take the short off.

fuel pump just needs to be connected to a battery to check that it chatters. By blocking first the inlet then the outlet the chattering should slow, but not stop. That's a simple go/no go. For a more rigorous test the inlet needs to be piped up to the pump by a couple of feet from a can of ideally paraffin, with the outlet going back into another container. The pump should deliver at least one Imperial pint per minute and in practice at least twice that in a continuous series of pulses with minimal bubbling. In this case by blocking the outlet the pump should stop, and not click more than once every 30 secs.
Paul Hunt

Russ - Paul's answer is correct if you have a complete fuel pump, however, if you have a broken down pump in pieces that is different. The 'coil' as you call it, is actually an electro magnet. You can bench test this unit by simply attaching a 12V battery to the two leads. The coil should produce a magnetic 'pull' that you can feel. The best thing to test the pull is with a .004 feeler gage as the coil only produces a small amount of current/pull. If you use a screwdriver or other tool you may not be able to sense the pull.
CCV Curt

" The best thing to test the pull is with a .004 feeler gage as the coil only produces a small amount of current/pull. If you use a screwdriver or other tool you may not be able to sense the pull."

Au contraire - The coil in a SU fuel pump, especially ones in the high pressure pump has to pull the diaphragm up against a spring that has a pressure of at least 2.6PSI up to 3.8PSI. A screwdriver held near either end of the coil will darn near be pulled out of your hand. Cheers - Dave
DW DuBois

It also takes about 7 amps, albeit just as a pulse when it clicks.
Paul Hunt

This thread was discussed between 25/06/2015 and 03/07/2015

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.