928 Forum
Sponsored by:
Sponsored by: 928 Specialists

1979 doesn't start at all, tried many things, now stuck :(

Old 07-11-2019, 03:10 PM
Join Date: Oct 2002
Location: Los Altos, CA
Posts: 562
Likes: 0
Received 0 Likes on 0 Posts

OP says there's 11 volts on pin 86 but infinite resistance on 85 -- and assuming that pin 85 was measured in P or N, that means a ground problem which I would attack first. (BTW I'm assuming that the measured 11V was not while the car was actually cranking, is that correct? 11V while cranking would not be an issue).

11 volts is a bit low though (again assuming that is not while the starter is actually cranking) so I would suggest, as the very first measure, ensuring that you have ground on 85. If you still have problems after that, then you'll need to start digging a little deeper into the ignition switch circuit. To do so, use the wiring diagram to figure out which line carries 12V going from the panel to the ignition switch, and compare it to the line coming back from the switch to the panel. This tests the condition of the switch and the lines to and from it. Do this as Dr. Bob suggested with the 14-pin disconnected so you don't actually start the car, just follow the thread I linked. On my '83 both of the lines to and from the ignition switch go through connector block A so it was very easy to locate and measure. On my car there was a slight voltage drop, but only a tenth or two as I recall, so if you're experiencing significant voltage drop across the switch with the above test then move on to investigating the switch and those lines. And finally compare the line coming back from the switch where it enters the panel (on my car at connector A), to the voltage at pin 86, that should all be the same (this will test the connection within the panel itself). I just did all this on my car, so see my linked thread above for more info.

The good news is that your bridge is starting the car, meaning that connectivity from the relay pin 87, out through Harness Number 1 to the 14-pin yellow wire and thence to the starter is OK.

To the OP, you simply need to start tracking down the above locations, it won't be hard to find, please report back what you find! Good luck!

PS If you haven't already done so be sure to unplug, inspect and clean and re-plug all your colored connector blocks -- that could also be a source of bad connectivity for virtually everything.

Last edited by rjtw; 07-11-2019 at 03:56 PM.
rjtw is offline  
Old 07-12-2019, 05:24 AM
Thread Starter
Join Date: Jun 2019
Posts: 5
Likes: 0
Received 0 Likes on 0 Posts

Thanks for the replies guys! Yes, 11 volts are measured in N and not running or cranking.
My first plan is to aim for the ground connections of the relay board and after that aim for the ignition switch.
Selector position I didn't think off but indeed also easy to diagnose once you already in the area
I will keep you posted but it will take some time..
Semjon is offline  

Thread Tools
Search this Thread

Contact Us - About Us - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.
  • Ask a Question
    Get answers from community experts
Question Title:
Your question will be posted in: