Is it worth repairing the fuel injection system yourself?

Pressurised fuel injection is used mostly in racing cars. But Volkswagen's engineers have been using a similar technology in production cars for decades now.

The injection unit is a fairly complex assembly, so its repair and servicing should be done at an official dealership. These days you can find an official Volkswagen service centre in almost any city. What engines is this injection equipment built for? As a rule, larger ones, of 1.5/1.6 litres. But so-called “small-displacement” engines are no exception either.

On this brand's cars, the injection unit is controlled by special air slide valves. And this is their fundamental difference from other manufacturers, who still fit their injection systems the old way, with throttle plates. Of course, air slide valves are a fairly high-tech product, but any Volkswagen service centre can diagnose and repair them. However technically savvy a car owner might be, repairing a system like this is quite labour-intensive for them. Judge for yourself: the slide valves sit inside a special housing. That housing, in turn, has four “funnels”. Their dimensions match the size of the engine. It's into these funnels that the injectors are screwed, as close to the edge as possible. This design feature helps fill the cylinders better. The injectors deliver the petrol-fuel mixture at an angle of thirty degrees.

It's worth noting that the air slide valves keep dirt out entirely, and so don't let the engine lose fuel. As is well known, an engine vibrates while the car is moving no matter how smooth the road surface or how good the engine mounts are. To keep this vibration from reaching the air slide valves, they're mounted to the intake pipe fairly elastically. If you've still decided to repair a Volkswagen yourself, it's worth paying attention to a few other details too. Keep in mind that besides the block with the air slide valves and funnels, the system also includes a fine filter, a fuel pump, and a high-pressure fuel pump, with a minimum pressure of 3 bar. The latter is driven by a toothed belt connected to the camshaft. Given all these factors, it's still better to leave repairing the system to the professionals.