PDA

View Full Version : Electrical Ignition coil hums, related to intermittent problem starting the car?



RichG
04-18-2016, 02:17 PM
Is it normal for the ignition coil to hum and vibrate slightly when the key is in the ignition and in the OFF position? Mine does.

I ask because my car has been having an intermittent starting problem for the past several years. It's what caused me to stop driving my car on weekends because I didn't want to get stranded -- which is prolly why one or more of my brakes are now stuck from lack of use. (That's another thread). :)

My battery and alternator have been replaced -- so I don't suspect those components. Many thanks to Dave and Tom from LINY DMC!

AAA reports nothing is wrong with my battery. Yet, often the car won't start. The relay doesn't even give a click-click-click sound. The battery has power because the headlights have full brightness when I turn them on to check. With the radio and lights OFF, if I hold the key in the START position for 30 seconds or more, once in every 10 times the car fires up. 9 times out of 10, I have to get a jump or recharge my battery.

When my voltmeter shows it is between 12 and 13, the car fires up like a champ every time.

Another factor: if I let my car sit for 2 days with the battery connected, the battery drains to the point where it needs to be recharged. Even a 2.5W solar panel isn't enough to keep the battery from draining. So, I use a battery cut-off switch in the interim.

I think I have 2 problems:
1) Voltage: some part in the ignition system is faulty causing my voltage to not be at the proper level to start the car
2) Current: something is draining my battery excessively (car alarm? stereo amplifier?) when parked

Interesting info: one time I had this problem at a DeLorean event. No click from the relay when the ignition key was turned to the ON position. Several owners came by and "hotwired" my car from the engine bay without giving me a boost from another battery. So, the battery had enough juice to start the car when part of the ignition system was bypassed.

content22207_2
04-18-2016, 02:46 PM
Is it normal for the ignition coil to hum and vibrate slightly

No (at least not one that isn't dying).

Ignition coils are backwards transformers. Remember when your childhood model railroad transformer started humming, before it died? Same principle.

Insulation on the windings is breaking down and disintegrating. Wherever they touch creates a short, reducing efficiency. Same thing happens to old electric motor windings.

Buy a new coil. They only cost $40 or so.

Bill Robertson
#5939

RichG
04-18-2016, 02:49 PM
Thanks, Bill. I'll order a new coil. If that isn't related to my starting issue, then at least it'll help prevent a future problem.

81dmc
04-18-2016, 09:24 PM
Thanks, Bill. I'll order a new coil. If that isn't related to my starting issue, then at least it'll help prevent a future problem.

If your looking for a coil, buy a 00012 blue coil here (http://www.ebay.com/itm/191556518804?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT). I dont believe resistors are needed with the newer Brazilian made coil.

content22207_2
04-18-2016, 09:56 PM
Any coil with 1.5 ohms or more of internal resistance shouldn't need external resistors.

Bill Robertson
#5939

RichG
04-23-2016, 09:42 PM
CORRECTION: it's my IDLE/LOW SPEED REGULATOR that hums when the key is in the ignition. I checked on another DeLorean and it hummed on that one as well. Normal?

81dmc
04-23-2016, 11:46 PM
CORRECTION: it's my IDLE/LOW SPEED REGULATOR that hums when the key is in the ignition. I checked on another DeLorean and it hummed on that one as well. Normal?

Perfectly normal.

Bitsyncmaster
04-24-2016, 05:19 AM
CORRECTION: it's my IDLE/LOW SPEED REGULATOR that hums when the key is in the ignition. I checked on another DeLorean and it hummed on that one as well. Normal?

Yes, normal with the OEM idle ECU. That is one of things I fixed on my idle ECU to shut down the idle motor if the engine has stopped. So if you have my ECU you won't have that hum.