He had a new co-driver in Jonathan Hirschi and the Swiss driver was on fire, holding second place from the moment the lights went out.
He pitted to hand over to Hartley. Seventeen laps later the car was still in the pits with another electrical/starter motor problem.
Once the problem was sorted the Kiwi reeled off a series of fast laps.
"I was really happy with my stint. I did the 10 quickest laps of the race - the fastest lap by over half a second. The car was very, very strong. We actually found an issue with the car this weekend that had been holding us back all year, so it's a little bit frustrating.
"We would have won the race by a long way if we did not have the issue and lost 20 laps. I think the rest of the teams would be very nervous if we come back with the same line-up next time."
The team finished seventh in their class and 25th overall, 20 laps down on the winners. Team owner Greg Murphy was as miffed as the rest of the crew.
"We could have won the race by an absolute mile," he said. "I'm sorry for the drivers. Brendon had the top 10 fastest laps of the race, which showed what we can really do. No stone will be left unturned to find the problem and make sure it does not happen again."
How Hartley and Murphy met is a story in itself. The young Kiwi had been out of a fulltime gig for a while after being released from the Red Bull junior development squad and was wandering around racetracks looking for a drive.
"I was down at Paul Ricard [track near Marseilles, France] at the first test the team ever did, and Brendon came over and told me he was looking for a drive," Murphy recalls.
"I asked him how much money he had and he said he didn't have any. Somehow I got stitched up by a couple of Kiwis and he got the drive.
"I'm so pleased I took the punt because he's unbelievable, really unbelievable."
Hartley has proved he can pedal a sports car as fast as anyone else.
"If you put a great driver like Hartley in a good car, the rest of the field had better look out. He's got a great future in sports car racing," said Murphy.
Endurance and sports car racing is the fastest-growing category of motorsport. The fields are getting bigger with more manufacturers joining the fray. The Americans have amalgamated their two series - Grand Am and the American Le Mans series - and the new United Sports Car Racing championship will be a big deal there next year.
"If Brendon does somehow get a really good deal to race in America next year, all I can do is wish him the best. ... As much as I would like to keep hold of him, I just want him to be the best he can and succeed," said Murphy.
Hartley gets another chance to show how good he might be this weekend with his Starworks team at the Grand Am's Brickyard Grand Prix at the Indianapolis Motor Speedway.
The next round of the ELMS is at the Hungaroring, near Budapest, Hungary, on September 13-14.
