G8RB8

Car used to start with a touch. I would say less than one revolution. The last two weeks it sometimes will spin like crazy but won't catch and run unless
I give it gas. Once it starts it idles and runs fine.
88s4 US

jej3

Crank Position Sensor? Fuel Pressure Regulator? I'm literally asking because I have somewhat similar symptoms.

Good Luck!

James Bailey

Actually instead of "giving it gas" you are actually giving it AIR ! pushing on the accelerator pedal simply opens the butterfly giving it more air. Not that I know what is wrong with your car

G8RB8

Fair enough. Never heard anyone refer to it as the air pedal though.

James Bailey

At least with a 928 it moves something Most new cars all you move is a potentiometer to tell the computers what you would LIKE to do...then it does what IT wants to do

gazfish

It allows manufacturers to include cruise control at almost no cost though

James Bailey

And of course gets us all closer to self driving cars as well as launch mode ,automatic blipped downshifts , traction control for the masses
Now why is this S-4 not wanting to start ????
Maybe the fuel is bleeding back to the tank and it is taking time to get fuel back to the engine ???Maybe try jumpering the fuel pump to build pressure BEFORE trying to start to see if that helps ???

docmirror

Happens when car is cold and warm starts? Or, cold starts only? Try running the car fully warm, shut it off, wait 10 seconds then crank it again.

Air may be getting into the fuel system and needs to be blown out while cranking until proper pressure is built up. Have a look at the entire fuel system from the pump to injectors while running and look for any small leaks. Use a high intensity white light on all fittings as it may only be enough to seep or drool if it only happens on cold start.

G8RB8

Warm and cold, but random. I've started trying to remember to watch for movement in the tach but it hasn't done it again yet.
I'll try your test this afternoon.

FredR

What voltage do you see when you switch on, and then cranking- both hot and cold?

Rgds

Fred

Brian'sIris

Could this be caused by sticky/leaking injectors allowing fuel into certain cylinders when the car is shut off?

Thus, when you step on the 'air' pedal, there is now enough air to allow the excess fuel to combust.

You could check by pulling spark plugs several minutes after shutting down, smelling or looking for fuel.

safulop

Yeah the fuel delivery system seems prone to tiny leaks at the injectors, causing the "starts with a touch" symptom, which it should not do. I think unless warm starting there should be significant crank time, your car is starting before the fuel pump is even running. Mine was doing this; I asked mechanic to check the fuel system for leaks, none were found. Yet when I completed an intake refresh with new seals etc., the car doesn't do that anymore. So my suggestion is injector seals.

Brian'sIris

I was thinking injector Cleaning, but also new o-ring seals and pintle caps are strongly recommended if they are very old or (gasp!) original.

Cheers!
Brian