2003 C4 Tiptronic won't start

[whito123]

My new to me 2003 C4 cab with tiptronic has run perfectly for 3 weeks. Yesterday I drove it 200 miles - (100 miles to my destination, 6 hour break, 100 miles home). Before I left I installed a new RemoteTop module, which installed easily and works as advertised.

This morning when I tried to start it, it wouldn't start. The battery "seems" full of power. The fuel pump "sounds" like it is charging the pressure properly when the key is turned. The starter turns the engine strongly, but no start up. Everything sounds correct and normal, but it is as if the engine isn't getting fuel.

I removed the cover to the fuel pump, and when I removed the fuel feed line (the fuel supply line to the engine), it did not seem to be pressurized. There is 1/3 fuel in the tank. When I had a pre-inspection done, the mechanic removed the same fuel supply line from the fuel pump connection and it sprayed fuel everywhere like opening a coke after it has been shaken. This time, no such pressure existed.

Like I said earlier, the fuel pump responds to the key being turned to the right (ie: just before I turn it far enough to engage the starter).

Should fuel spray out of this connection due to pressure when I remove it? Is this an indicator of where my trouble is?

Please give me trouble shooting suggestions if you can. I'm learning quickly about this great car, but so far I'm stumped...

Thanks.

[Loren]

Start by checking for fault codes.

A bad crank sensor or something similar could cause this.

[whito123]

Sorry I neglected this piece of info: using a Durametric cable, I receive NO fault codes at all.

Disconnected and reconnected the battery as well.

Installed new Fuel Pump Relay. Checked fuse C4.

Still no fire-up...

Edited June 4, 2011 by whito123

[whito123]

OK, take a look at these two screen captures of Durametric actual values. The two shots are before I turn the key to "start" and after I try to start the car. Is the immobilizer value telling me something?

Before starting attempt

After starting attempt:

[whito123]

OK, here's the next thing I've tried. I unhooked the fuel supply line on top of the fuel tank sending unit, and hooked up a piece of clear tubing and put the other end in a jerry can. I then turned the key to prime the fuel pump / line. The pump sounds like it is trying to work, but I don't know if the sounds are the correct ones... not a drop of fuel came out of the sending unit though...

The dealer (not a genuine P dealership) said they had installed a brand new fuel pump the week before I picked it up (3 weeks ago). Does it sound like the fuel pump is bad???

[whito123]

Update: Thankfully, I figured it out!

I kept going back to the fact that there didn't seem to be any fuel pressure starting at the sending unit in the tank. I decided to investigate the sending unit further, and opened it up and removed the sending unit thinking that I'd need to get the fuel pump out to probably bench test it somehow (before I laid out $400 - 500 for a new one). Something didn't look right with the sending unit however; there was one "nipple" that didn't have a connection to it. I felt around with my hand and found a loose hose, connected it to the "empty" nipple, and put everything back together. I turned the key to prime the fuel pump, and then before starting it I thought I'd check for pressure again in the sending unit fuel supply line. Sure enough, as soon as I disconnected it fuel sprayed out (I had a towel ready just in case covering the whole thing). Plugged it back in, turned the key all the way, and she fired right up.

What a great feeling to figure it out, and to not have to spend a dime on a tow, new fuel pump, or worse.

I wonder what the dealer would have done had I had it towed.... new fuel pump...? new relays...? new "Johnson rod"...? or would they have figured it out the way I did and charged me for an hour's work???

Anyway, thanks for reading my posts and for the suggestions to diagnose.

[judgejon]

nice going!