Austin Reed

Hi all
Just bought a 4000s a month ago. Was trying to fix diff lock (vacuum line disconnected at distributor) and when I lowered the car from the lift and tried to start to check the lockers, it would idle for 5-10 seconds, and then die.
Fuel pump runs, has gas, and battery is charged.
Before I put on the lift, it fired right up and I took it for a drive, less than 3 hours before it would not start.

I found a thread about this same problem, but had no solutions or ideas.
Wondering if anyone has any ideas to help?

Austin Reed

Heres a pic of the old A4 and the new 4000

audi-driver1126

Check all your vacuum lines around the throttle body. These cars are very vacuum sensitive. Im thinking maybe during the process of checking the vacuum lines around the distributor you could have bumped something. Not all the hoses are clamped on so they could easily fall out and cause this issue.

Austin Reed

Thanks for the help. Will try that tonight. Does the hood sticker have every line on it? Bought the Bentley but won't be here until the 23rd.

Rogviler

At least with these, vacuum is vacuum so it generally doesn't matter how the lines are hooked up, unless they're supposed to go through a switch, such as for the differential selector. Be glad you don't have an old Mercedes where certain components need restrictors to change how much vacuum they get and there are amplifiers and modulators to worry about.

I would also make certain that your fuel pump is still working all the way up until the engine dies. If the pump stops before the engine dies then you could suspect some bad wiring, relay, or Hall sender. Of course then it goes into not actually being related to the work you did, which can be harder to figure out sometimes.

I'm thinking vacuum too though. A way to test would be to basically disconnect (and keep track of) all the lines and then plug the holes at the intake. If it starts, then plug things back in one at a time. Also look for tears on the intake boot, especially the bottom. Lastly, if all else fails, test the system with smoke (the cheap cigar trick) and you'll see any leaks right away.

-Rog

Austin Reed

Thanks for the tips. Vacuum seems hooked up. Will try cigar trick and wait for Bentley to come.
Here is a video of it running if anyone has experienced this before.

https://goo.gl/photos/nVuZNjGpXQAA9dB48

Rogviler

It definitely seems A/F related. You'll have to go through the vacuum stuff thoroughly. I tested it once and just a 1/4" opening can cause the car to not even start, so you could be looking at a very small hole or crack.

-Rog

Austin Reed

Turns out two wires that connect to the intake manifold to ground out were broken off. Wired together and fixed. Red and a red with brown stripe. Thanks to all who helped

Rogviler

Well, it was A/F related...

The ECU connections are an often-overlooked problem, either those grounds or the #24 fuse. Glad it was easy, and at least now you know everything else is in order.

-Rog