I have a 1998 Chevy Silverado. Just recently it started acting up, I would turn the key and it would crank but never fire up. I applied the brake pedal and sure enough it fired right up. But as soon as I let off the brake the truck dies. Any ideas?
Any aftermarket security system?
No aftermarket security
The only thing we know is somehow the brake light circuit is supplying voltage to the secondary ignition system. And the secondary ignition system circuit isn’t.
Look at the bulkhead connector at the firewall for the under dash fuse block.
I have to say, that is definitely puzzling. There’s often a safety interlock with automatic transmissions that require you step on the brakes before the engine will crank, so it is possible there’s something with that function that is awry. Why it would crank but not fire up though, have no idea. But that would be the first place I’d start if I had this problem with an automatic equipped vehicle, test if that brake safety interlock was working correctly.
One other idea. When you step on the brake, that activates the brake booster, which is vacuum powered. So maybe there’s some kind of problem with the brake booster, or the booster is ok, but activating it is causing something to happen in the engine vacuum system to allow the engine to start. For example the fuel pressure regulator is usually connected to the vacuum system, so the fuel pressure regulator is another thing to check.
I’ve never seen a vehicle with an automatic transmission where you must step on the brake pedal in order to start the engine.
Every automatic I’ve seen, requires that the brake pedal be depressed in order to shift the transmission out of park.
Yes, my mistake, you are 100% correct Tester. The safety interlock prevents shifting out of park until you step on the brake.