Sometimes when it’s cold out, my car will take a few seconds to a minute or two to let me start the engine from the run position. The only dash light that’s on at this point is the seatbelt reminder, the rest stay off til it can start. It turns over just doesn’t start. Why is this? Regina 740 1990.

 

when you turn on the ignition, ALL the warning lights on the dash should light up, then they should go out when the engine starts and the alternator kicks on.

if thats not happening, I'd suspect your ignition switch

 

when I turn the ignition, only the seatbelt warning lights for a bit. They come on after a bit then I can start it. It’s only when it’s cold though and no amount of knocking the dashboard or jiggling the key helps.

 

as I said, sounds like a flakey ignition switch. the ignition switch has a bunch of different outputs.

I suppose it also could be the wiring from the 'positive terminal' to the ignition switch but then the seat belt light probably wouldn't be seeing power, nor would the starter turn over, so that rules that out.

the ignition key switch is a stack of 3 things... there's the actual lock cylinder, there's the mechanical bits that lock the steering column, then there's a rotary electrical switch on the back of it, which has 1-2 circuit 30 always-power wires into it, and a whole bunch of switched power wires out of it going to different circuits, including circuit 50 (starter), circuit 15 (ignition), circuit 15X (accessory), and so forth. these cars are 25-35 years old, that switch wears out.

this is the switch for later 240/740/940 https://www.fcpeuro.com/products/vol...80-940-9447805 (generally all models with airbags, pre-airbag 240's use a different switch)

her'es a whole write-up on them
Notes on Ignition Switch and Lock

 

Or it could be the circuit board in the back of the panel, it acts in weird ways when the soldering points get cracked, lights off/on, etc.

 

true, but would that prevent the car from starting? I mean, I know the alternator wont bootstrap without D+ current through the battery light, but the ignition and fuel injection power doesn't go through the dashboard

 

OK, but the car starts, only takes it a little longer meaning it is cranking over. And in COLD weather this is common and it seems unrelated to the dash lights' issue. It can probably do with a tune up or even a better battery.

 

k, i don't have wiring diagrams on a 1990 740, but I do have for a 1991, which should be close enough...

the power to the instrument panel comes from the 15R terminal of the ignition switch, and goes via a blue-red wire to connector D (3) pin 4 on the instrument cluster

that same blue-red 15R circuit goes to the ECU which uses it to decide when to turn on the fuel system relay so if the 15R output of the ignition switch was flakey, then you'd get exactly the symptoms you describe, no dash warning lights, and cranking without starting.

the seat belt reminder light gets its power from ignition switch 15I and a blue-YELLOW wire, so a completely different circuit.

15R is on in Drive (II) and Start (III), while 15I is only on in Drive (II) and goes out temporarily when you twist the key to Start (this is to minimize current drain while the starter is running).