1980 928 Registering your 928

My 928 was driven a few days ago. I tried to start it today and got no fire. I added some gas since it was low and it still turns over fine but does not start. As it is turning over all the 
dumb dumb lights go out  as expected except the O2 sensory. I'm just curious if an O2 sensory would make it not fire at all, or is it likely something else?  

Thanks for help.  Jim

Hello Jim,

The O2 sensor isn't likely the cause of your no-start condition.  There are multiple possible causes.  I always suggest looking at relays and fuses first.Look to your Owners manual to identify the positions of these items.XVI Fuel injection (AFC) 928.615.119.00XVII Fuel Pump 928.615.113.01#22 Fuel pump fuse  25 AmpThe fuses on these older 928s are subject to corrosion, I suggest removing the fuses (one a t a time) and inspecting them and cleaning the fuse tips and the fingers where they fit on the fuse panel.The relays are special relays and you’ll need to obtain them from a Porsche Specialist parts supplier as normal parts sales companies will not have them.  Even if the relays haven’t failed I suggest replacing them as they have carbon points and are failure prone.If you are mechanically inclined, the way to test the relays is to remove them and insert jumper wires and see if the engine starts.  If it does, put the relay back in and if it doesn’t start that has identified a failed relay.  A jumper wire should have a tip similar to the relay pins.  You can find the socket positions by looking at the schematic on the relay and the impression at the relay pin.The wiring convention for the Porsche 928 is terminal 30 is always 12V (direct connection to the battery) and 87 is the switched circuit.  In the case of the fuel injection relay (also labeled in Porsche documentation as the AFC relay), a jumper will need to have 3 wires for socket positions 30, 87 and 87A.  If the relays and fuse are not at fault, you need to determine if you have spark.  If no spark, that must be corrected as the RPM signal generated by the spark module connects to the L-Jetronic fuel injection module and the fuel pump relay.  If there is no RPM signal there will be no fuel injection and the fuel pump will not turn on.  You also should look for vacuum leaks, as they can also cause a no-start condition.  In my 1983 928 I had a large enough leak at the throttle body to cause a no-start.  If yours is an automatic transmission car, there are caps on the passenger side of the throttle body can with age can fail.  If yours is a manual shift 928, there are short hoses from the throttle bode that connect to a deceleration damper and those (and the damper) can fail.A shop that is familiar with Porsche 928s may assist you.  These 928s are quite different from the 911, so just because a shop says they service Porsche they may not know about the 928.  If there are no Porsche specific shops available, a shop that services 1980s Volvos may be able to do the work as the L-Jetronic  fuel injection system is similar.
 

Hi Rich: 
I’ve read your recent detailed  technical post in response to my apparent lack of fuel pump operation on my 1980 928. You have an amazing knowledge of these cars and you have presented it in a well thought out manner. Can I call you professor from here on?

I’ve located the fuel pump fuse and the fuel pump and injection relays. I have a mechanic friend coming over this morning to help me
jump the relays and hopefully address the possible vacuum leaks relating to the fuel injection and spark issues if we are unable to find the previously discussed easy relay fixes. My 928 is a 7,000 mile manual transmission car that has been kept inside its whole life but being 42 years old I think that vacuum lines and 1980’s plastic under duress should cause me some anticipated maintenance problems. 

Regarding your email about registering my 928:  I entered the VIN when I recently signed up for 928 Owners Club. Am I correct in assuming that this takes car of my car registration that you addressed?

Jim



 

Hello 1980928,

To add your Porsche 928 to the 928 Owners Cub Registry, follow the instructions from this link:

www.928oc.org/928-registry/registry-faq

We have over 3200 Porsche 928s.  Your very low mile 1980 would be a nice addition.  You can add your story and photos.