JHolt55

I've got a 1986 Audi 4000s, 1.8 inline 4. It's got issues, it's had issues since it was bought that have only gotten worse. Currently the fuel pump has been replaced, the car was bogging down, smelled like gas and had little to no power. With the new pump the car still has little power won't rev out unless you let it sit for a couple minutes but after a couple revs it doesn't want to go above idle. It no longer smells like gas out of the exhaust though.

My questions are as follows. How on earth does this fuel system work? There is a pump in the rear, and some kind of block on the airbox that splits to the injectors. What's with that, is it a second pump or just a distribution system? What else could be causing the low/zero power issue? Can someone lend me a hand and explain.

Rogviler

Ho boy, it's a deep dive when you start learning about the fuel system on these. To answer some of your questions, the distribution block on the airbox matches the amount of fuel going to the injectors with the amount of air flowing through the airbox. It's basically a valve controlled by a flap that moves up and down with the airflow. It doesn't know when the cylinders are firing, it simply provides fuel continuously to all the injectors (continuous injection system or CIS). It is highly sensitive to both vacuum leaks and gunk in the fuel system.

If I had to guess, it sounds like you might have issues with the injectors being worn out or clogged and they're not opening and closing properly. You can get injectors new still, and either way I'm sure you'll see a benefit if you change them. But there are also several things along the fuel system that can cause issues like that, including a clogged or sticky fuel distributor, usually the "valve" part right in the middle, which consists of a plunger and a cylinder that has holes in it to distribute the fuel. Many times people have good results with unscrewing the fuel distributor and cleaning the plunger from the bottom with carb cleaner until it moves freely.

Gregar

These CIS systems cannot be allowed to sit for long. Old gas can clog up several elements. I suggest pulling injectors, jumping the fuel pump to see how injectors are working. If injectors are suspect, replace them and take Rogs advice. If injectors are gunked, very likely fuel distributor valve is also. Bentley manual is vital to working on these captivating cars. Welcome aboard!