There’s nothing more Aussie than a group of young blokes on their P’s, loading up their rigs and heading bush for a camping trip.

 My son, Khobey, had just joined the club, fresh P-plates in hand and his pride and joy finally back on the road: a 75 Series LandCruiser he’d rebuilt from the ground up.
 (If you’ve been through our workshop in the past year, you’ve probably seen it parked out back.)

Diffs rebuilt. Cab and tray painted. After months in the shed, he’d been driving it a week and was itching for its first proper adventure.

 He wasn’t alone, two of his mates had also just got their P’s, each in their own rigs. One of them, funnily enough, was in another 75 … but petrol. And as it turned out, both 75s were destined for a bit of drama.

The Setup

The boys left Newcastle on the Friday, Khobey’s Cruiser freshly filled with diesel. They set up camp at Mungo Brush, and by Saturday were topping up at a local servo before taking a run out to Seal Rocks and down Lighthouse Beach.

That’s when the cracks appeared.

On the freeway back, Khobey’s 75 started losing power, not just sluggish, but struggling to hold 50 km/h. Now, picture a red P-plater crawling along the highway in a farm-spec LandCruiser. Other drivers weren’t exactly patient. The “helpful” horns and hand gestures rolled in thick and fast.

First Attempt at a Fix

I got the call and drove up Sunday. By this stage I’d already had my senses confused: Khobey’s mate’s petrol 75 parked nearby had a fuel leak, so when I stuck my nose in Khobey’s diesel 75, I thought I caught a whiff of petrol. With that other rig leaking, I chalked it up to cross-contamination of the nostrils.

Looking back… I should’ve trusted my nose.

I had a service kit from the shed, but of course it was missing the primary filter. So I swapped only the secondary. Straight away, the Cruiser came back to life. Off we went for a beach run, thinking we’d nailed it.

But not long after, same loss of power. We jury-rigged the primary out of the loop as a test, and the 75 ran fine for the rest of the day. That pointed squarely at blocked filters.

Limp Mode, Round Two

By the time Khobey packed up camp, the writing was on the wall. Twenty minutes down the road, the 75 was coughing and crawling again.
 We went through the motions: changed both filters this time, drained 20 litres from the tank, and refilled with clean diesel. That gave him enough to limp toward Newcastle.

Home was in sight — but again, same story. Filters clogged. By Mayfield West we’d had enough; dropped the tank, gave it a proper clean-out, and started fresh with new diesel and filters.

The Smoking Gun: Petrol in the Tank

When we drained the tank properly, the truth came out. What flowed out wasn’t diesel with a hint of petrol, it was almost all petrol, with a dash of diesel at the bottom.

Here’s the technical bit:

• Petrol is lighter than diesel, so it floats on top.
• That 20 L of fresh diesel sitting at the bottom was enough to keep it running (sort of).
• When you drain a tank, you usually draw from the bottom — the densest layer. At the workshop, what should’ve been diesel looked and smelled suspiciously like petrol. “Well-off petrol,” as we joked, and it was evaporating off the floor pretty quickly.

The likely scenario? He ended up with petrol contamination (somehow) instead of diesel at that servo near camp. The small amount of diesel that remained settled underneath, enough to run short-term.

Add petrol’s solvent action into the mix, and it gets worse:

• Old tanks like that 75’s are lined with years of varnish, gum, and silt.
• Diesel leaves it sitting quietly. Petrol strips it off the walls like paint thinner.
   All that sludge gets pulled into the filters — which, credit where due, did their job and clogged solid before the rubbish reached the injection pump (including the suction strainer in the tank).

Why the 1HZ Survived

A modern common-rail diesel wouldn’t have lasted five minutes in this mess, petrol would’ve destroyed the high-pressure pump in short order.
 But Khobey’s 1HZ, even with its aftermarket turbo, is an old-school indirect-injection motor. Brutally simple and far more forgiving.

The main drama wasn’t lubrication loss (though petrol is no help there), but plain fuel starvation. The filters clogged, the pump was starved, and the motor had nothing to burn.

Clean tank, new filters, fresh diesel, and she was purring again.

Lessons from the Shed

• Trust your nose. If it smells like petrol, don’t ignore it, even if another rig nearby is leaking.
• Petrol and diesel don’t mix. Petrol floats, strips tanks clean, and clogs filters fast.
• Filters are heroes. They sacrificed themselves and saved the injection system from a world of hurt.
• Old tanks hide surprises. Years of silt and varnish wait patiently until something stirs them up, and petrol is the ultimate stirrer.
• Go all the way. Swapping filters bought us time, but the real fix was dropping and cleaning the tank.

The Punchline

Two 75s head out for a camping trip: one petrol, one diesel.
 The petrol 75 came home on a tow truck thanks to a stuffed clutch.
 The diesel 75 nearly came home on a tow truck thanks to petrol in the tank.

Both made it back, both taught their drivers a few lessons, and both gave us stories worth retelling in the shed.

For Khobey, it was his first taste of bush-mechanic diagnostics, roadside filter swaps, and the brutal honesty of other drivers who don’t appreciate a red P-plater crawling up the freeway at 50 km/h.

For the rest of us, it’s a reminder that sometimes the biggest dramas in a diesel engine don’t start with the motor at all, they start at the bowser.