Fuel leak? Sorted. Occasional misfire? Ah...

Wise mechanics will tell you that 90% of fuelling problems are actually ignition faults, but for once conventional wisdom didn’t apply to my Mercedes. While hunting down a persistent and long running (seven years and counting) misfire at idle – and getting nowhere fast – a petrol line somewhere underneath the car let go and turned my garage into a potential bomb. With the fuel spillage hastily cleaned up, I crawled around on the soggy floor looking for the culprit.

The leak was coming from somewhere up above the rear subframe, where the petrol feed line comes from the pumps before it snakes back down and runs along the bottom of the nearside sill, carrying its precious and vital cargo up to the 5-litre

V8 engine. I poked about for a while getting soggier and soggier, and while it was all great fun, you can have too much of a good thing. Eventually – actually quite a decent amount of time before that – I got sick of the sogginess, the bits falling in my eyes and my complete inability to see a damn thing, and gave up. Figuring that the closest I was going to get to pinning down the leak was within a few feet of it, I decided to go for the scatter gun approach and just replace the entire section of solid fuel line that I couldn’t see.

While I was at it, I took all the hoses and pipework off the fuel pump assembly (two pumps, an accumulator and a filter). I took these to a hydraulic pipe specialist and asked him to make some replacements – it had to be cheaper than the vast sums the Merc dealer wanted for the parts, although I suppose I should be grateful that they are at least still available. Grudgingly grateful will have to do. The pipe specialist still charged me £120 for three short rubber pipes though – hardly a bargain, but cheaper than a new car following a fire.

The options for buying Merc spares in the UK have become very limited in recent years. A lot of German-based suppliers can’t be bothered to sign up to the UK Government’s VAT collecting scheme, so no longer ship to this sceptred Isle. There’s a useful Americanbased specialist, but they won’t send parts to the UK unless you spend what they consider a worthwhile sum with them. In this instance that wouldn’t have been a problem, as they can supply a complete pump assembly as outlined above, including hoses and

ABOVE: Will’s 1987 Mercedes 500 SEC pillarless coupé has its original K-jet mechanical petrol injection, plus a custommade LPG injection system.

ABOVE: Two pumps, one accumulator and a fuel filter make up the assembly – plus some expensive new hoses.

ABOVE: The fuel pump cradle parts stripped and cleaned.