Metering head

Took the metering head of the GTI today to check it due to various fuelling problems. Quite easy, just a case of removing a lot of fuel lines. Top tip - leave fuel filler cap off to ensure tank remains de-pressurised. Didn't work this out at first and had petrol gushing out of the return line under low pressure fom the tank 8O . Almost filled a litre jug before I realised my error :roll: .

All the connections and ports look very clean as did the petrol which came out of it, but you can't see inside the ports so its hard to tell what ots like inside. I assume I would have seen crud coming out of it or in the ports?

The central piston was also very clean and didn't appear worn, however it didn't travel the full length of the chamber smoothly. Anyone know if this is a problem? Piston seems to catch a bit two thirds out of the chamber, but is a tight fit when pushed furthe in. Don't think it would ever get to this position when connected up. Going to leave it to soak in carb cleaner for a couple of days before refitting.

Out of interest has anyone taken a metering head apart and tried to recondition the internals. Seem to remember someone posting a while ago that they did and that they couldn't get it back togther without leaking? Also the four little hex key dusk gaps on top of the metering head appear to have adjusters underneath each one. Never heard seen these referred to before. Anyone know what they are for/how they work?

Cheers

Seem to remember reading in the Haynes that if the central piston is not a smooth sliding fit then its pretty much a new metering head if its casuing problems   .

There was a thread on the old forum about dismantling and reassembly of a metering head. but not sure if the old forum limk works anymore. As you rightly point out though the person that did this then had loads of problems with leakage after reassembly.

Chris

The four pressure differential valves are there to maintain a constant pressure drop at the metering slits as the control plunger changes position. Without them, the pressure across the slits would alter, thereby affecting the metering of the flow to the injectors.
I would say they are pretty reliable, and do not need maintenance. They are quite sensitive (they maintain a pressure differential of only 0.1 bar - (about 1.5psi). Stripping them down may result in the settings being disturbed on re-assembly - so they're best left alone IMO.
Geoff