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MG ZR ZS ZT Technical - Humming and Screeches .. I have a theory.

The 'Humming' thread over on MGF Technical was of interest to me. I have a theory:

I sometimes notice a continuous 'hum' in my ZS long after engine switch off. Not always noticeable and it does sound like a 'distant' EFi pump priming up, but a much fainter sound than that you hear for a second or two when switching on the ignition before starting.

By the way, I always wait for the pump noise to stop before operating the starter. No real evidence but from observations of other cars and their owners starting techniques, I strongly suspect that operating the starter BEFORE the pump has primed up sometimes results in damage to the starter ring. The screeching noise of a starter failing to engage properly is horrible. Over a period, the teeth on the starter ring (usually the same teeth as engines often stop in the same position each switch off) become severely worn and damaged.

One neighbour's Jaguar screeched horribly each morning waking me up as he tried repeatedly to start it - the sound of a starter pinion failing to engage in the worn teeth properly on the starter ring was horrible...... his repeated attempts to get the car to start resulted in ever more damage to that area of the starter ring teeth. It was so bad one morning, I got up and showed him that by putting the car in gear, moving it a foot or two forward, moved the starter ring to an unworn area of ring teeth where the car would start immediately. Done the same with other cars which have obviously been mistreated, possibly by owners who are guilty only of being ignorant of the way things work under their car's bonnets.

Invariably, the car and not the ignorance of the owner gets the blame.

How do others see this?

JMcF.
John McFeely

>>the teeth on the starter ring (usually the same teeth as engines often stop in the same position each switch off) become severely worn and damaged.

I had this on a Montego of mine once! (non MG 1.6)

When starting my ZS I turn the ignition on, wait for the for the pump to prime, as you suggest John, though I was not aware I might be reducing ware!

Kelv.
Kelvin

surely worn ring gears went out with pre-engaged starters becoming the norm...
David S

surely something as important as this should be built in to the car? - like a two second delay switch until the pump has finished, or the pump completes the ignition sequence when it's done it's stuff.

I keep meaning to follow your example John, but so far, I only remember after the car's started. Car starts, then I say "Oh B*gger!"

I can't help noticing your enduring interest in cars. According to Honest John, this is one of the main factors in happy car ownership, and trouble free longevity of the car itself. Again, something I notice you tell us about your cars.

Cheers -
Gary
Gary

Pre-start oil pumps are available for engines that increase the life of the bearings. The ignition switch first activates an electric oil pump to pressurise the oil circuit to ensure is pumped to the bearings to avoid dry starts. There have been some good case studies for the benefit of these.

FWIW
Martin
Martin ZT

>>>>>surely something as important as this should be built in to the car?

Unless it's not important? I too have a lot of respect for John but I can't see any benefits here.

>>>>>>I strongly suspect that operating the starter BEFORE the pump has primed up sometimes results in damage to the starter ring.

Can't see how John. Can you elucidate? I've had loads of cars, and never had a problem with starter rings even on my 40-year-old racing engines.

In the meantime yes I get into my ZS and wait for the petrol pump to prime but only because I've been driving a diesel for years and I've got into the habit of switching on and putting on my seat belt while the glow plugs operate ;-)

Max
Max T

This thread was discussed between 29/08/2004 and 08/09/2004

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