Dead ignition, then starts ok

andy625uk

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Sep 23, 2023
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Southampton, UK
Vehicle Details
Thunderbird LX 4.6v8 1994
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This morning I went to start the car, turned the key and it was completely dead. Ignition lights came on but didn't start. Battery isn't flat. Tried two or three times and nothing, then the next time it starts s normal. I didn't manage to hear if there was any clicking when I tried the times it was dead as I had the windows up. I'll see what happens later when I have to start it again.

I know my ignition switch is worn, just wondered whether that could be causing this, or if it's the starter.
 
My guess is it's more likely the starter than the ignition switch. Based on a similar situation on my '95 4.6. Almost like the system is slow getting electricity to the starter. Sometimes I'll turn the key to on, all dash lights come on as supposed to, then turn the key to ignition but sometimes there is a pause of up to almost three seconds before the starter cranks the engine. I think it's a weak solenoid, that it's taking a while to build up the magnetic field to activate, but its been like this for several years and I am yet to connect up some test equipment. Light running a test lead from the solenoid to inside the car and then watching the meter or test light to see if it is the delay is from the ignition switch to the solenoid or from the solenoid to the starter.

Yes it could be the ignition switch, contacts not being fully contacted each and every time the switch it turned to ignition. Could be a slightly maladjusted neutral safety switch? Rather than trying the ignition switch a couple three times if at first it doesn't crank how about holding the ignition switch in the on position for an extended period to maybe differentiate between the switch and something further down the circuit?
 
Yes, I also think of the MLPS (neutral safety switch) on the side of the transmission in these cases. Easy to test - try moving the shifter into neutral, or just from park into manual 1 then back to park to see what it does.

When the MLPS is preventing the engine from turning over, when you turn the key all the electronics go out with no clicking or other sounds until you release the key back to on. That's by design and controlled by the ignition switch. If you have electronics still when you try to crank, that would point more towards the ignition switch than MLPS.
 
I have experienced a similar situation after an engine swap. The MLPS connector wasn't fully seated and the car would power up but turn the key and everything went out. The ignition switch could also be the culprit.

Here are the MLPS and ignition switch testing procedures from the factory manual, and the wiring diagram of the starting system.

Screenshot 2024-07-25 075551.png

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Good ideas. I have had issues with the neutral safety switch before. I'll try that first - doh! Didn't think of that earlier.
 
Start by jumping the starter with a cheater switch. If it bumps fine a several times, its not the cable or the starter. Next, switch batteries, don't rely on the current voltage, mine said 12.5 but was intermittent just the same. Use a VM meter to see what voltage you have before running, then check when running to see if your alternator is charging the battery, should be about 14 running. The culprit on mine was both a battery that seemed fine and the ignition switch. If you have another car like your car, swap ignition switch's to see if that is the culprit. That is how I found out mine was crap. Good luck!
 
Went to move the car tonight and it started ok, so I think I'll monitor it for a few days.
 
Battery and heat do not mix well at all. Have you checked the fluid level in the battery cylinders? If it is low, add ONLY distilled water till it makes an upside down bubble (full to the top in side mark).
 
Ok again this morning. I reckon I must have left the shifter in slightly wrong position.

Thanks for all the suggestions though. When the car's nearly 30yrs old, something or other is going to go down at some point!
 

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