mctb

Today ive just checked all the relays and fuses and all ok, car turns over but i still have no spark have checked at the coils and i have nothing not even 12v at the + terminal both cols are brand new Bosch coils. Any ideas out there

gazfish

Both coils get power from the ignition switch via the central electrical panel, no fuses or relays involved. If you’re no seeing battery voltage with the ignition in the run position then there’s a cabling issue or ignition switch issue. Google wiring diagram for Porsche 928, there’s free copies available to trace the connections. Best of luck.

ROG100

CPS or the connectors at the harness.

Kiln_Red

Check that the 2-pin plug (green wire, white wire) isn't disconnected. This plug is in the passenger footwell with the CE panel.

Wisconsin Joe

Ok, I'm going to ask how you 'checked' the relays. Do you have a relay tester? Or did you just swap them around (you can use the horn position as a 'test' - If the horn honks, the relay is good).

Is your alarm disarmed? If it's armed the car will not start.

When did it last run? What did you do to it (if anything) since then?

Are you getting 'tach bounce' when you crank it? The tach should bump up and down a little bit when the motor is cranking.

Are you getting fuel injector pulse? Check with a noid light.

FWIW, I had a 'no start' on my 85 S2 a month ago. No spark, no injector pulse. Changed the EZF & LH relays and away I went.

mctb

Tested relays via tester

Alarm disarmed

3 years

yes bounces

Have 12 volts at the ignition switch two black wires no power at the coils or the relay ignition feeds but all the diagrams i have looked dont seem to match my CE board

byrdman454

The relay diagrams you will find on 928gt.com or most other web searches will be the US model version. The Euro S2 model is completely different. It also has a different fuel injection system, different injectors with different impedence, and twin distributors. Here is a list of the relays for the S2 with part numbers.

VIII - EZF


IX - 928.618.109.00 Kick Down (auto)
928.615.125.01 Bridge (5-speed)


X - 141.951.253.B Horn


XI - 928.615.124.00 ABS


XII - 141.951.253.B Fog Light


XIII - 993.615.101.00 Wiper System


XIV - 141.951.253.B Starter (auto)
928.612.473.00 Bridge (5-speed)


XV - 928.618.113.01 Intensive Washers


XVI - 141.951.253.B LH-Jetronic


XVII - 141.951.253.B Fuel Pump


XVIII - 141.951.253.B Fan


XIX/XX - 928.618.107.02 Headlight


XXI - 141.951.253.B Blower


XXII - 141.951.253.B Defroster

Landseer

Unless very new, I'd Replace CPS and pay special attention to connector integrity. Bouncing tach doesn't mean CPS is good, I've seen this more than once. Wave form can be read with scope, but most folks don't have them.


Clean computer and injector grounds:
On euro 84 all engine control grounds are attached to pass side cam/valve cover, two different ground points, quite subject to corrosion due to dissimilar metals. This and intermittently ad CPS caused o start problems for me with 84 euro over the years.

Also check little positive wire at battery. Battery must have full charge.

You can jumper the relevant relays to take them out of the picture. And can bypass alarm with a jumper too, search for these procedures using Google and ref rennlist, more reliable than search function usually.