I recently just bought a great driving beautiful B5 A4.

Randomly a couple days after buying it, It just wouldn't start.

Eventually I went through all the steps to troubleshoot and realized that the fuel pump wasn't priming or activating when I turned the key. I jumped the fuel pump relay and heard the pump kick on and car still didn't start.

I ended up going in my ecu box and wiggled and pulled on the wires just a little bit and then it started up.

This happened at least 5 more times randomly and most of the time (hot or cold) would start up no problem.

Anytime I have driven my car, it has never shutdown or bogged out. The problem only came randomly when I have tried to start it.

It happened again this morning and now I can get it to start at all.

I have yet to look at any codes my car my be sending out. I have to wait for someone to bring a code reader over since I can't bring my car anywhere.

Could it be a bad computer? even though it is fine when it is running?

I'm at a loss...

 

It sounds like a simple (wiring) connection. Not necessarily simple to fix, but that's what it sounds like to me.

I had a brand new fuel pump put in and it immediately wouldn't start cold. Hot? no problem. I found out that the new pump had a bad diaphragm and since our cars prime electronically (for 2 seconds), I have to try to turn it over once, then try again before it will start.

See if that's happening to you.

 

It's not sparking and the fuel pump doesn't engage unless I jump the relay circuit... even then, still nothing.

 

Did you check all of your grounds?

 

Yeah checked all the grounds for sure... I ended up bringing my car to a diagnostic place. They literally charged my battery then my car started right up... they checked the alternator and battery and they are both good. I think I know what happened though... The trim with the seal that sits below my windshield is completely loose and by no means stops water from running into my engine bay. Though the ECU is covered i still think if enough water gets into that area around where it's mounted to the car/ firewall that water still can get in slightly. Whatever I did when I was messing around with the grounds and all the connectors might have helped also. I think i fixed it when I was messing around with it, but by the time I did, the battery was too dead to start my car. Any thoughts?

 

Yeah, Tape that **** up! lol.

I have that same crappy, plastic weather stripping and it's more important than it seems. You have your cabin air filter right up against the bottom of the windshield (opposite the ECU), you obviously have the ECU & harness and another big one is access to the cabin. That's why it's so important that we keep our engine bays clear of leaves, etc. I've heard horror stories of guys who have had their entire floors flooded because of that.

What I did was take off the entire (two piece) plastic piece and used a razor blade to cut the smallest part of the top edge off, just enough to get rid of the old crusty edge and create a clean, "new" edge that compliments the angle of the windshield, then I cleaned everything real good and put everything back on, made sure everything was snug and in place (as stock as it could be), then I duct taped the **** out of it. lol.

My car is black, that piece is black and I bought a huge roll of high quality black duct tape off ebay for like $8 and I started just below those bullshit screw lock pieces, using pieces as long as possible (you don't want to make a huge straight line when it's ultimately going to be curved. I started from the bottom and worked my way up as high as I could get on the windshield, overlapping by 1/2 a strip. Working your way up and overlapping gives you the best protection. Just make sure you stay away from the wipers, because you don't want that sticky **** gets on your wipers - and don't use a razor blade to cut the tape on the windshield.

I hope that helps.

G/L