I’ve been in the process of restoring a 1986 mk2 GTI 8v CIS Kjet. I have done an excess amount of work on it and after fixing the vacuum leaks I am having trouble keeping the engine running. The list of new parts are listed.
-New fuel distributor
-New fuel lines
-New 5th injector
-New fuel pumps (both)
-New injectors
-New Distributor, wires, and plugs
-New ISV
I have cleaned up the grounds the best I can. Both fuel pumps prime. But I have to wait 24 hours to start the car. After 24hr it starts up quickly it hunts for idle 200-ish rpm for a minute or two and smooths out. The car runs incredibly rich. I pulled the spark plugs and they were caked in carbon from the fuel. I’m at a loss at this point. It’s either the fuel differential module or something else. I’m banging my head against the wall. Each step I take is going to the right direction but I’ve hit a wall.
You've said you've done the Fuel Distributor, but have you done the Warm Up Regulator?
The WUR ultimately controls the fuelling based on how hot the car is, if it has failed, it'll almost certainly cause you massive problems.
You can also try unplugging the 5th injector, these have been known to cause more trouble than they're worth, I run with mine unplugged on my quattro and it starts much better.
I had a similar problem.Turns out the fuel pressure regulator was at fault. Look at the clear pipe that goes to the air box if you can see fuel in it there should not be.