While my buddy was getting tuned, we swapped over from my series 1 EMS which we cruised 6 hours to the shop on to a new series 2 EMS which he purchased from the shop. While setting up the dyno, the ignition fuse popped and replaced it. After that during the tuning, we had no issues and got a great tune.

We left the shop and got some food. When trying to start the car after we ate, the fuel pump wouldn't prime and I couldn't connect to the series 2 EMS on my computer. We swapped back in my series 1 EMS and it would start and connect fine. The main relay would repeatedly click with the key out of the car with my series 1 EMS, but would go away when the key is switched to the on position. We swapped back in his series 2 EMS and it would not prime again and wouldn't connect. We ended up switching back to my series 1 EMS to get back to the hotel.

The next day, the shop owner came back to the shop on Easter to help us try to figure it out . We even swapped to another new series 2 EMS and it still had that issue. We could get the pump to prime on the series 2 EMS after power cycling it until it would prime. Sometimes it would only take a couple of power cycles and sometimes it'd take 10 minutes of cycling it. We checked all grounds and they're good, especially the G101 ground on the back of the cylinder head. It had this issue for both cold starts and after the car is fully warm.


Any ideas? We were thinking it was maybe his battery relocation in his trunk or maybe it needing some more grounding points back by the battery. He used 4 gauge wire and we were gonna redo it with 0/1 gauge wire. If not that, maybe a new main relay?

 

Check all the engine and ECU grounds. I have had v2 boxes do this when a ground came loose.