So my last motor had no compression in one of the rotors (I forget front or back). And when I pulled the motor apart for a rebuild it was a stuck apex seal, which might of been able to fix w some ATF or whatever to loosen it up. Oh well. However, for the 5 years I drove her on and off she always started right up even when hot on the stock EFI.

So I swapped in a motor from another running TurboII that I wrecked last winter. This motor started right up everytime even in the dead of winter on a Blow Thru Dellorto.

W the used known well running motor now in the car, using stock EFI again, she starts fine when cold, however if I try to restart after shutting down when hot, she cranks and cranks and cranks w no start.

I searched and came up w installing a switch to kill the fuel pump which gets her started again when hot but sometimes not easily.

Anyone have an idea WTF could be causing this...???

 

The two likely answers are (in order) leaky fuel injectors or low compression.

Leaky injectors bleed fuel slowly into the engine after you shut the car off. Then when you try to start the car, it's been flooded and is hard to start. Based on the fact that you installed a switch and it helped, this is likely at least part of the issue. The switch is a bandaid fix, but a proper fix is removing the injectors for cleaning and then reinstalling them.

The other possibility is low compression, but having injectors serviced usually costs less than $100 so I would start there.

 

as said before, it’s due to leaky injectors. I had the same problem with my s4 na.

You never mentioned if you are using s4 or s5 electronics.

I think s5 has the option to allow you to hold the throttle at 100% when cranking which will tell the ecu you are trying to de flood the engine and it will not inject fuel.

if I’m wrong, I’m just spoiled with an apexi pfc.

But hey, why not check compression anyways. Might as well pull the plugs and check them out. I’ve had spark plugs get fouled out from flooding engines.

 

I believe you are right. I had leaky injectors a few years ago and there was a window in there that it wouldn't start unless you floored it. Overnight it was fine. If it set for half an hour or so you had to floor it. I can't remember if it was the FSM but somewhere I read the de-flood procedure on the S5 was to hold the accelerator to the floor while cranking as it would stop the injectors from injecting fuel.