After finally upgrading to the plastic fuel tank on my 1990 Puch 460 diesel, I decided to tackle something I’ve been meaning to do for years — install a diesel lift pump. And let me tell you, the difference is night and day.
The Bosch mechanical injection pump used in these old diesel G-Wagens is a marvel of analog engineering — entirely mechanical, no computers, just precision machining. It draws fuel from the tank using suction alone, relying on a small internal lift mechanism to pull fuel all the way forward through filters, lines, and any air bubbles or restrictions along the way. The problem is, it was never designed to deal with modern fuel blends, aging hoses, or tank swaps. By adding even a small amount of positive pressure from an external lift pump — say 4–6 psi — you’re giving the Bosch pump a much easier job. Instead of sucking fuel through a long, potentially leaky run, it’s now being fed a steady, pressurized stream. This keeps the injection pump cooler, reduces cavitation, and eliminates hard-start problems that come from air intrusion or fuel drain-back. It’s the kind of simple tweak that makes old-school tech feel modern again.
I went with a 24V Facet Cube solid-state pump (12V versions are avaible), mounted low and tight near the tank, tied into the existing fuel pickup line coming off the new vertical sender with an inline filter.
You can simply disconnect the existing rubber hose from the fuel supply metal tube (top is supply, bottom is return), connect the pre-filter to the hose, run a short hose from the filter to the lift pump, then a short hose out from the pump to the metal tube. I ran 14-gauge automotive wire in a sleeved jacket alongside the factory harness, grounded it properly, and tied the power into a 5A fused circuit on the fuse block. The three fuses on the right side of the fuse box are tied to the ignition.
What I didn’t expect was just how transformative this simple addition would be.
Starting is instant. Throttle response is sharper with more power. Cold starts no longer involve that hesitant sputter — just a clean, confident idle. Even after long sits or filter changes, the system now primes itself while the glow-plugs warm pre-chambers without a hand pump or cracked injector lines. In fact, after swapping the tank, I was able to fully bleed the system simply by turning the key (but not cranking) and letting the pump push fuel through. Took maybe three minutes for the bubbles to vanish.
I also added a proper tank vent with a rollover valve, routed up high and out of the way, to keep the pressure system happy and sealed. More on that in a future post.
While I installed this system on my W460 G-Wagen, the benefits apply to any rig running the OM617 or OM617A diesel engine — whether it’s a G, a W123, W126, or anything else in the Mercedes diesel family. In fact, any pre-1990 W460 diesel with the stock mechanical draw setup would see improved performance, easier starting, and faster priming with a low-pressure lift pump added to the fuel system. It’s a worthwhile upgrade for anyone still relying on the original suction-only setup. That said, gasoline-powered G-Wagens don’t need this mod — they already run electric fuel pumps as part of the factory injection system. But if you’re on the diesel side of the fence, especially with aging hardware, this is one of the best quality-of-life improvements you can make.
The old iron just keeps getting better.
