This is probably the beginning of several small articles about electrical issues I've run into and solved.
On my 64 after maybe a year of sporadic driving a problem arose with the EFI. The system would, during random times, go through what is called a "Reset". It's like I turned the ignition key off and back on quickly while driving. This caused the ECU to go through the afterstart enrichment, fast idle and, of course, the car jerks and the system shuts off and comes back on. Very errattic and very difficult to drive in any traffic.
My first thoughts were to look for a ground issue. All this checked ok. Second I checked the 12V connections. These were good too. Last week I decided to fire it up and drive around the neighborhood. Really to keep the tires from flat spotting. While driving around the block several times the car ran fine. I had changed my idle settings in the ECU from "Closed Loop" to "Open Loop" thinking maybe the fault was with the idle valve. Maybe shutting down for an instant causing the "Resets". I decided to take it out to the main road towards our Loop 410. I hit 3rd gear in a spirited acceleration and there she goes, Reset. On my laptop the system showed "Not Connected". So no power to the ECU. Stopped the car in the median(during rush hour traffic; really fun!). Messed around checking for power at the ECU wiring. Ultimately found the main relay dead. Luckly I had a pair of new 4 prong relays wired into the power top motor wiring. I swapped these and the car ran.
So here's the problem and solution. I decided to use some solid state Hella relays #H41773001. 4 prong, wiring and prong position on the Hella website looks the same as the Bosch type I initially used. These Hella relays are "Made in the USA". Very Nice! I ordered these from McMaster-Carr. This place is an extremely nice source for many different items. The relays arrived in the Hella boxes. But, no wiring schematic and no prong numbers anywhere on the relay. Hum... So, of course, I plugged the first relay in and the fuel pump starts running. (I use 2 relays, 1 main and 1 fuel pump. The main relay triggers the ECU which, in turn, triggers the pump relay) The ignition key is laying on the seat. Not in the switch. So the relay is either faulty or the prong positions are different from the Bosch type. Well, yesterday I decided to test the relay. My multimeter showed continuity on only 2 pins. But this was a momentary continuity. I figured these were the "switch" prongs so one should be "86" or power from the ignition switch and the other "85" used for the ground. The other will be "30" with 12V with the remaining "87" going to the "load".
The Hella website shows a prong position for these relays that is incorrect. I also searched and found several forums discussing this same problem but without any info on the correction. Most guys just suggested going with more Bosch type relays. Some also said the solid state relays would run really hot. I'm here to tell you these relays are awesome. My car runs fine, no more "Resets" and once I got back I checked the relay temps via the finger test and they were at ambient temp. I didn't detect any heat. My old relays were very hot to the touch. The SS relays are pricy but so far well worth it.
Bosch type relay schematic from Hella
My wiring solution
My solution above leaves the "87" position alone but the remaining 3 need to be repositioned. I just popped the wires out of the relay mounting block and plugged them into their new homes.