savantauto

Does anyone know if the relay that causes the delayed shut off has any impact on the engine's ability to restart?

Kaefer

Yes it can. If the relay has failed depending on how it failed it can prevent power from going to the CDI (ignition) box. If you do a search the relay plug can be jumpered to get the car running but then it'll stay running until you remove the jumper.

Edit for more info: When you turn the key on do you hear the CDI box whine? If yes then most likely the delay relay is ok. If no CDI whine when key is on then it's possible the delay relay is bad.

savantauto

Thanks for the info. Actually found out that my relay is missing!

Once I replace I hope starting will be easier.

Mark Houghton

Well then your problem is something else besides the missing relay. Usually when those relays fail they simply stop giving you the time delay between turning off the key and the engine stopping. But I suppose they could fail the other way to where you get no power to your ignition at all.

Either way, since you don't have one and the car has been starting, you don't need one. Something else is causing your issues.

savantauto

Thanks. What is the actual purpose of the relay? Even though car starts, I thought it might be easier if I had it. I suspect my fuel injectors are also adding to the problem.

Mark Houghton

It delays - for a couple of seconds - disconnecting the ignition to the CDI after you've turned off the key. Thus, it will bleed down and burn any residual fuel left in the injector lines. The car will continue to run until the fuel pressure in the lines drops, or until the timed circuit in the relay shuts off the power to the CDI. You'll think the car is 'running on' or 'dieseling', but it's just burning up the rest of the gas.

savantauto

Ok, I now understand what it is supposed to do, but what is the reason for it? Also, does it serve any purpose for restarting the engine?

Thanks

Mark Houghton

It's only there to help relieve fuel pressure in the lines at shutdown. These CIS injectors aren't electronically controlled solenoids (or frequency valves, or whatever) like modern injectors. There's simply a pintle held closed against spring tension that opens when it sees fuel pressure and sprays continuously. With age, the springs weaken and/or the pintle seat gets dirty to where they don't seal properly, allowing a slow drip of fuel after the engine is shut off. I believe this is the reason Porsche put the relay in to guard against that, though in my mind it's overkill.

It serves no purpose in restarting the engine. My relay had been bypassed by the previous owner when installing MSD ignition, with no ill effects for many years. I've been too lazy to re-wire it back into the equation.

savantauto

Got it. Thanks for your help!