 Intermittent failures are the most frustrating, Relays can be gremlins |
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| ctc911ctc |
 Jan 20 2020, 03:12 PM
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Senior Member  Group: Members Posts: 1,124 Joined: 9-June 18 From: boston Member No.: 22,206 Region Association: North East States 
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All,
My son took the '74 2.0 to school when it was 15 degrees. Started right up in the garage, at the end of the school day it would not start. I met him at the school and recharged the battery. 1. The starter cable was not tight enough - this was one problem 2. Intermittently the Fuel Pump relay would not run when the key is turned. Turned out when I got the car back to the garage that the initial fuel pump run was not happening every time. Since it did happen when we were looking at this as a potential problem we were then focused on the wrong things. Within this forum, there are notes stating that the computer should "Pull-Down" the ground (connect) to the Fuel Pump relay to energize the relay. I could not get this to happen on Pin III of the wires coming from the computer to the relay board in the engine bay. HOWEVER, I was able to put in a headlight relay and get fuel pump to operate EVERY time out of 20-30 key turns. Not sure the PullDown language is accurate. This said the relay being energized can be affected by temperature. This exercise would caution everyone that old relays should be removed from the critical equipment chain. I had a very similar experience in 1974 with my 1970 1.7, where it would not start after a date at midnight when the temperature was minus 15. The next day, when it warmed to +20 and I re-charged the battery I was able to start the car no problem. |
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| Superhawk996 |
Jan 20 2020, 04:06 PM
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914 Guru Group: Members Posts: 7,028 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch
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(IMG:style_emoticons/default/agree.gif) Intermittent electrical conditions are the worst!
Great job troubleshooting it. (IMG:style_emoticons/default/biggrin.gif) Don't forget to to check all grounds both to the engine and also between the body and the transmission. |
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| 914Sixer |
Jan 20 2020, 05:29 PM
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914 Guru Group: Members Posts: 9,123 Joined: 17-January 05 From: San Angelo Texas Member No.: 3,457 Region Association: Southwest Region
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The old relays are mechanical step switches.
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| porschetub |
Jan 20 2020, 10:09 PM
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Advanced Member Group: Members Posts: 4,816 Joined: 25-July 15 From: New Zealand Member No.: 18,995 Region Association: None |
Had huge grief with fuel pump and FI control relays a while back...I understand your pain,luckily I have a few spares, I tested them and binned the bad ones to save confusion later.
Pulled 2 bad ones apart and the contacts were burnt and due to lack of use there was corrosion on those contacts,one had stuck contacts and the other was not energizing I think due to resistance. When I get back into my car again I will be ordering 914rubber replacements ,heads up to Mark for doing these ,current testing shows they will well out live most owners (IMG:style_emoticons/default/smilie_pokal.gif) . |
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