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MG MGA - Radio suppression

My old car radio (radiomobile 50T) picks up the regular ticking of the fuel pump. Is it usual for the pump to cause interference and can I fit a suppressor (type?)to the live supply wire or is it an earthing issue?
J H Cole

The SU fuel pump has a coil and points. Anytime you switch current to a coil through points you will cause an arc. The arc causes radio interference and also burns up the points. Various versions of the SU pump use capacitors and diodes to suppress the arc.

Anyway, to supress the radio interference the first thing to try is to add a capacitor right at the fuel pump. You could try something like this,
Just about any capacitor would help, even a spare ignition points condenser. Just wire it at the pump between the power wire and the ground.

Hopefull Dave Dubois will have some more suggestions as he seems to be the resident SU pump expert.

Jeff Schultz

JH - You probably have a very old pump that doesn't have the capacitor in it used for arc suppression or possibly the swamping resistor in the pump (internal to the coil) has burned out. Go to a local electronics store and get a 0.47 microfarad capacitor and attach it between the power terminal of the pump and ground as Jeff suggests. That should get rid of the noise for you. Cheers - Dave
David DuBois

Radio suppression: B exhaust manifold to sidepipe through thrush muffler...
Russ Carnes

I like Russ's idea more than the electronic approach. I have only one question .... what's the muffler needed for?
dominic clancy

Dominic, I live in a small town, have coffee with the local fuzz. Muffler makes it seem that I at least try to play by the rules!

Indeed, a cap from + to ground will help suppress the arcing at the pump points. Additionally, check to make certain that the battery ground point to the chassis as well as any other chassis ground points are clean, rust free and making solid contact. A high impedance ground can actually make electrical noises worse.
Russ Carnes

This thread was discussed between 28/06/2009 and 05/07/2009

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