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IGNITION LIGHT TAKES 10 MINUTES TO COME ON

879 views 12 replies 7 participants last post by  Ianwright40 
#1 ·
My 1980 450 SLC is difficult to start in the morning.

After leaving the key in the ignition the ignition light will finally come on after 10 minutes.

Otherwise, the car will usually run fine .
During the day, after initial start in the morning there will be a delay of a few seconds;
ie the ignition light does not come on immediately like it should.

The problem does seem to be temperature related; ie when it is cold in the morning the engine
will not fire, since the ignition light does not come on this means no spark available.

The starter motor turns engine no problem, but I must wait 10 minutes in the morning
with the key turned in the ignition. Once the ignition light comes on the car usually starts
since then the spark is obviously coming through.

I must also point out that the fuel pump noise is also not present; when the ignition light
finally comes on the the fuel pump noise can be heard when you approach the vehicle.

YOUR HELP WILL BE APPRECIATED
 
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#3 ·
Hello Weather Man - -

I suppose more accurately it is the battery/charging light.

What I meant is that although the charging and battery is perfect it seems that the engine won't fire
unless the "battery/charge" light comes on first.

The engine cranks without a problem and starter motor is fine.

Under normal circumstances the battery/charge light comes on immediately and after a few seconds of course goes
off as soon as it detects the charging is OK.

I don't have circuit diagrams but I am guessing the ignition and possibly even fuel is cut off so the engine won't fire-
but there is clearly no spark since the engine just cranks:

As soon as the battery light comes on the car usually starts without a problem.
It just takes about 10 minutes with the key in the ignition and THEN the battery light comes on-
As mentioned you can also then hear the fuel pump,

SORRY I think I got a bit hung up on the fact that there is no ignition ie spark UNTIL the battery/charge light comes on.
Once it comes on, I can proceed to turn the key all the way and the car usually starts and drives perfectly.

It is totally baffling and really makes no sense,

As I say, if I can get the battery/charge light to come on it starts and drives without a problem.
The next morning it's the same thing; the car is cold and the battery/charge light does not come on.

Wait about 10 minutes- the battery light comes on and then you can start, the engine fires, and the car is usually OK for the rest of the day.
 
#9 ·
This may sound really crazy, but.......I have a 1981 280SL. When I bought the car and brought it in to the States, it had right at 43,000 miles. At 48,000 miles, the voltage regulator (brushes) went out. Same thing happened at 96,000 miles, and then again at.....you guessed it, 144,000 miles. As in Weatherman's case, the battery sustained operation for a little while but not for long. I already have the new regulator anticipating 192,000 miles, at 186K right now.

That said, I don't really believe your situation is likely related to the voltage regulator since, as you say, after the power finally comes on you drive without issues. IF it were the voltage regulator, you would wind up without juice after driving for a while (especially at night, when you have lights on draining the battery even more) and the vehicle would stall since the battery would not be charging.

My guess is you have bad contacts somewhere, so start with the battery and work through the system from there. Have you tried a different battery? That would be your quickest test. Or, just take it to any Autozone and have them run a diagnostic on it. Beyond that you would need an electrical schematic that shows your circuits so you can start testing each one. Also, with the key in the ignition at the ON position (not start), have you tried moving the key ever so slightly in one direction and then the other? Some play in the switch can definitely create issues as ejboyd5 suggested. After I have started my car and am going down the road, if I want to turn the blower motor on I have to very, very slightly move the key about 1/8" counter clockwise, not enough so the car stalls, and it comes right on. I need to address that at some point, but haven't had the time lately and besides, I know how to make it work....

Best of luck to you and let us know how it goes.
 
#10 ·
Hello ANOVAK - -

My thinking is that the most likely cause (not including bad wiring) is the ignition switch or the voltage regulator.
I don't have the circuit diagram, but I think these are the "2 units" circuit-wise that could stop the ignition light from
coming on initially.

The voltage regulator may give a partial short? on switch-on, which may explain the 10 minute delay- indicating that the semi-conductor works but is not 100%?

It seems rather strange that a bad connection can consistently give a 10 minute delay- I would suspect that bad connections
would be more sporadic?

A faulty semi-conductor might "drag down" the voltage initially, but might be OK once it "takes" after warm-up.

I'm putting my money on a semi-conductor that might be ready go completely or the ignition switch, or of course wiring or contacts in the "ignition/battery globe" circuit ?

Regards,
 
#11 · (Edited)
Yes, what you say makes sense although I'm not well-versed enough in electronics to speak knowledgeably about the semiconductor thing. The easy thing is, next time you have her started and running, is to proceed to Autozone and have them test the battery.....just to rule that out, or in. Free and easy and it will give you more information.

The symptoms I've experienced with voltage regulators have mainly to do with a drained battery once they go bad since there is no longer a charge when the brushes are too short to make contact. Doesn't sound like the issue to me, but I'd like to know just the same.....always something to learn with these cars!
 
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