Refuelling was a problem for the #88 in the race at The Bend. Image: InSyde Media
Whincup led the early laps and sat second to the eventual race winning Brodie Kostecki/Todd Hazelwood Ford when a lap 24 pit stop put the Red Bull Camaro out of contention.
The seven-time champion emerged from that pit stop cycle 20 seconds behind Hazelwood and was forced to pit again for fuel just over 10 laps later.
“We came in for fuel and we’re sitting there for fifty seconds with no fuel going in,” explained Whincup post-race.
“We’ll have to analyse it when we get back, but we think there was fuel in the vent which was stopping the air from escaping so the fuel could go in and fill it up.
“It was like a hydraulic airlock creating compression in the tank so the fuel couldn’t come in. That was basically our day.”
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Whincup lost further time when he speared off the road in his final stint, before Feeney took charge and eventually greeted the chequered flag in 19th place.
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“The rest of the day we were just trying things,” said Whincup.
“We were doing things with the set up just trying all different lines and all sorts of things just like a bit of a test session after that pit stop issue.
“We were always going to be running around at the back of the pack after something like that. She was a long old day out there, unfortunately.”
Whincup had been overhauled by Hazelwood during the first stint and conceded the car did not have the pace to contend for victory regardless.
“There was no sign whatsoever all weekend that we were weren’t going to have the pace in the race but ultimately that’s what happened… we just didn’t have the pace,” he said.
“I got off to a good start, we led from the start and had clear track, but I just got mowed down by the DJR car and then Frosty (Mark Winterbottom) was coming as well.
“He was going to be a big problem of ours in the second stint regardless and we saw that coming.”
The sister #1 Red Bull Camaro of Will Brown and Scott Pye climbed from a lowly 16th place qualifying effort to finish fourth.