My friend has a 1990 vw fox and recently she would drive it for awhile and it would just die...She would have to wait as much as a day before it would start again...It's a four cylinder(I don't know the size of the motor). She has had many people try to fix it...So far the fuel pumps, fuel pump relay, Coil, Ignition module, heating/cooling sensor and other basic tune-ups have been replaced with no effect..If anyone has any ideas, I would appreciate hearing them..

Does this happen when it is cold out or an any temp? Aprox. how long will it run before it dies? Does it just start to idle ruff and then die out when she hits the gas? Just looking for a trend here...

I have had the same exact prob - I at first I thought it was the fuel pump relay since the gauge, tach, fuel pump, starter, cold start, and all these other things were connected to it - replaced that, replaced the fuel filter, pump (both in the gas tank and the one outside) the fuel accumulator, even the distributor, eventually the problem got fixed - it was the fuel pump - and the accumulator - but the rest was replaced just in case - what I had to do though in order to get it running was when it started up I had to press on the gas to get the gas flowing to the injectors - because what happened was there was too much air and not enough fuel to ignite a decent enough spark - my cold start valve was also replaced (very important if you even wanna get a turn outta the engine in any weather) but until these parts were replaced I had to balance out the air fuel ratio by giving as much fuel as there was air until the proper compression needed from the engine that the faulty parts werent doing normally manually - this usually only takes about a few minutes if its done right - it'll be hard at first - the colder the worser of course - but I couldn't figure this out nor could my mechanic - just started reading a bentley book and put two and two together and now I have a better fuel system than when I first bought the car! :) If you start driving the car from a cold engine from the start you'll get hesistation and sputtering because the improper amount of air and fuel has been allocated - it usually ran until I left it off for at least an hour - hopefully this helps you both - I would make sure that both the pump in the gas tank and the one outside are both replaced at the same time because one could fault another useless to malfunctioning

It all depends what your friend has for a fuel system. I have an 89 fox with cis-e fuel injection and I had the same problem. I took it to a vw specialist and he found the differential pressure regulator wasn't working correctly. This part is rectangular, and is screwed onto the side of the fuel distributor. The fuel distributor is the part thats connected to the engine with steel braided hoses. Now if you feel a little adventurous, If you unplug the differential pressure regulator I think the car should start. Now theres no guarantees to that only because it was a while ago when I had it done. Good luck