Intermittent failures are the most frustrating, Relays can be gremlins Options

[ctc911ctc]

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.