Recently bought a 2003 a4 quattro 1.8t and upon delivery the guy went to boost it and hooked cables up wrong, won't start since. So I tried fuses a d relays, there's no spark or fuel, I can get fuel pump to turn on but have to jump it. Whirls over good just doesn't start. I have exact car for parts tried computer but that didn't do anything. So my question is, what am I missing, something, whys my fuse box half powered and how to test computer to see if it's cooked

 

If I'm not mistaken, there is a relay panel in the engine compartment, and one in the dash behind the panel where your left knee would be when sitting in the driver seat. Did you check both? Don't quote me though, it's been some time since I had my B5, and I've never messed with a B6. But it sounds to me like you're missing a relay of fuse somewhere.

On another note, if your ECU is fried, the check engine light will not come on when the key is in the on position... If the CEL comes on and stays on, the ECU should still be good.

 

Car ran great until it was backwards, I believe all relays are in correct positions

 

Believing and checking are 2 different things. Check all your fuses and relays again. Also, hook up a diagnostic tool to the obd2 port and see if it has power etc....if you have one. I'm going to guess you won't be able to communicate at all with any of the modules.....

Try and look at fuse 7 on the end of the dash fuse box, it's a mini fuse. Look at that fuse VERY carefully AND the wires behind it....

Jumping a car backwards can cause serious damage to a bunch of electronics on an Audi/VW if the fuses don't protect it....

 

Ok ill try that, I've tried three different computers n nothing, no power to fuel pump fuse or engine control unit fuse, I have the same car for parts should I replace fuse panel

 

What do you mean by 3 different computers? If you're talking about the the ECM and you swapped those out, just remember they either have to match the part number EXACTLY and/or need to be reprogrammed for your car-so put the ORIGINAL one back in. If there's no power to any of the modules, fuel pump,ECM etc...there IS a fuse or RELAY (or melted wires) somewhere.

Check that 7 fuse and let me know.

Check your fuses with an ohm meter as well.

Before swapping fuse panels and throwing parts at it, find the issue first.

 

I'll try that n get back to you later, I appreciate the help :-)

 

It was that fuse, a brake fuse, thanks again :-) you saved me a headache

 

It runs, but ecp light n check engine light are on now, runs like crap no power at all?

 

Now you're going to have to SCAN it for codes. As stated, when you jump a car backwards...it can do a lot of damage....there's probably some other issues to work out now.

By no power, do you mean it idles rough or while driving?

Scan it and post the codes.....and we can go from there....