Delayed Ignition Cut-Off Relay

[A930Rocket]

While getting my car running again and finding out I couldn't run without the Delayed Ignition Cut-Off Relay, I started to think it might be good idea to carry a spare one of those in the car along with spare fuses, relays, etc. Mine has a 1987 date stamped on it, so it's getting long in the tooth.

Then I started thinking, what if I bypassed it? I'm not even sure it was working before with the MSD, as it never seems to run on for a second after shutting it down. I realize it's to burn any left over gas in the cylinders, but what's the long term effect? I know Porsche wouldn't have installed it for grins.

On another note, can it be jumped like the other relays in an emergency?

[mark houghton]

Originally Posted by A930Rocket

While getting my car running again and finding out I couldn't run without the Delayed Ignition Cut-Off Relay, I started to think it might be good idea to carry a spare one of those in the car along with spare fuses, relays, etc. Mine has a 1987 date stamped on it, so it's getting long in the tooth.

Then I started thinking, what if I bypassed it? I'm not even sure it was working before with the MSD, as it never seems to run on for a second after shutting it down. I realize it's to burn any left over gas in the cylinders, but what's the long term effect? I know Porsche wouldn't have installed it for grins.

On another note, can it be jumped like the other relays in an emergency?

You know, I've been thinking on this for quite some time, and pretty much just said phuque it. I have the delay relay, but it's never delayed like it should. So, I figured it was defective and bought a new one. Guess what....I now have a spare that doesn't do anything either. Upon further inspection, I finally realized that the PO who installed my current MSD didn't bother to draw the power source from the relay output. So, the relay won't do a garsh-darn thang unless the MSD is hooked in-line with it, so it can delay the interruption of power to the MSD.

Net-net, who needs it to start with? I suppose that old injectors might be prone to leak down into the cylinders over time, but I figure it just gives a nice pool of raw gas sitting in the heads or on top of the pistons to aid in starting!

[A930Rocket]

I didn't even know to wire mine into the power source from the relay output. Did you change yours when you found it?

A few seconds of running isn't going to help a leaky injector I would think. It would burn what's there, stop and then continue to leak.

How much was a new relay BtW?

[mark houghton]

Originally Posted by A930Rocket

I didn't even know to wire mine into the power source from the relay output. Did you change yours when you found it?

A few seconds of running isn't going to help a leaky injector I would think. It would burn what's there, stop and then continue to leak.

How much was a new relay BtW?

Nope, never fixed the wiring. That's on my list of things to do, low priority. I don't recall exactly, but they're not that expensive. $30-$40 maybe. Actually, I think I found it NIB on eBay for a bargain price.

[Jim2]

The delay relay has a small capacitor across it's coil input legs. When the key switch is turned to "on" the relay coil is energized via the light gauge red/black wire. Upon shutdown with the key switch this capacitor continues to feed power to the relay coil which in turn keeps the relay contacts closed thereby continuing to feed power to the CDI until the capacitor discharges. Very simple.

I've been under the impression it's intention is to run the motor until the pressure in the fuel accumulator drops off so the injectors don't drip after shutdown. You certainly can jump it if needed. Long term effect? who knows.

[JFairman]

Thats good information about how the delay relay works.

The MSD has a thick red wire for it's voltage amplifier and storage caps and a smaller red wire for turning it on and off.
The thick red power wire is good to wire to the + terminal of the starter motor with a fuse inline. If you have the MSD on the firewall the starter motor is about a foot away.

The smaller red wire turns the MSD on. If you plug it into the terminal in the 6 pin plug in the factory harness that also turned on the origonal CDI than the MSD will be going through the delay relay circuit.

Or if you want to bypass the delay relay you could run a wire to the MSD from a fuse that is powered on at the front fuse panel with the ignition switch or from the ignition switch with or without a seperate relay.

You could probably just modify the wiring at the delay relay socket to bypass it's effect too.

[A930Rocket]

I have my thick red wire hooked up at the starter. No fuse, as I don't recall it calling for one. Next time I'll run it to the battery.

The thin red wire is plugged into the 6 pin CDI plug.

The thick red power wire is good to wire to the + terminal of the starter motor with a fuse inline. If you have the MSD on the firewall the starter motor is about a foot away.



The smaller red wire turns the MSD on. If you plug it into the terminal in the 6 pin plug in the factory harness that also turned on the origonal CDI than the MSD will be going through the delay relay circuit.

[sundevil64]

I wired in my Crane HI-6n with the relay in mind. Does this relay control the fuel pumps at all? I'm trying to trouble shoot a problem.

Thanks,

John

[equality72521]

Originally Posted by sundevil64

I wired in my Crane HI-6n with the relay in mind. Does this relay control the fuel pumps at all? I'm trying to trouble shoot a problem.

Thanks,

John

No, it just provides electricity to the CDI for a short time (as the capacitor discharges) to delay engine shut down for the fuel reasons mentioned above. The pumps have already shut down at this point to prevent them from continuing to push fuel.