badinstincts

I have a 2001 A6 2.7T Tip Quattro. In the morning or anytime after the car has been sitting off for over an hour it wont start on the first try. It cranks and cranks but wont start, sometimes it kinda will, it will be at an extremely low rpm and seem to die off unless I give it gas, but it seems bad so I just crank first for 2 seconds then turn it off, then it will start right up on the second try like normal.

I just changed the spark plugs and oil, but that didn't help.
The only issue with the car is that my secondary air pump seized and I took it out and am going to rebuild, but I know that is not the problem.

Any ideas?

joshe8695@yahoo.com

try replacing the coolant temp. sensor

frankinstyn

Yup. Exactly the problem

badinstincts

hmm, I just replaced it last summer. you really think it could be bad already?
I did have a coolant leak like 6 months ago, and I didn't bleed the system like I should have after...

SloopJohnB@mac.com

check fuel pressure with a gauge. Leaking injector(s) or check valve will drop fuel pressure and fuel won't happen.

badinstincts

not saying your wrong, but wouldn't there be fault codes for engine running lean or insufficient fuel flow? i just dont have gauges and have no idea how to check fuel pressure, but i also feel that there would be a code for that.

SloopJohnB@mac.com

Depends on how the software was written. Things like a leaking injector or insufficient fuel pressure for instant startup might not set a code since the engine isn't on when these things happen. Codes are generally set when engine is running, not necessarily starting, especially if the engine starts and pressures come up.

Here's the real deal...not everything can be done by reading a code...sometimes you have to go old school and get your information the hard way. Fuel pressure øn a fuel injected engine happens to be one of the primary bits of information. It would be nice if vag-com could log fuel pressure over a few minutes of time, say from the time you turn on the ignition (not twist start) through the key twist to start and then to a few seconds after the engine starts.

That's somewhat different from just looking for a code.

SloopJohnB@mac.com

vag-com will log fuel pressure.
http://www.vaglinks.com/OBDII/Vag-co...d_Graphing.pdf

Zaphodb17

I'm wondering if you have two problems. If the fuel injector rail is bleeding down over a period of time, i.e. 1hr-24hrs, and the fuel pump is not triggering via its relay, on the first cranking period, this could be what you're describing. Usually (but not always) the FP relay gets a timed "run" trigger signal from the ignition switch and then once the engine fires, the "FP run" signal comes from the ECU. If there is no "Engine Running" signal from the ECU, since the engine doesn't catch immediately, the fuel pump relay will probably reach the end of the timed signal and shut itself off. Keying the ignition switch a second time starts it all over again and that may be why it finally starts. However, the ignition switches (the electrical part, not the key lock part) in these cars are not failsafe and that might be a contributing factor. Keep in mind that the above is theoretical and pretty simplistic, but I'd bet that the leak-down of the rail pressure is your main problem. Usually, fuel pressure remains at a predetemined level for quite awhile after switch-off and it does not sound as if your fuel pressure is staying up. You'll have to determine what's bad, your ignition switch, your fuel injector(s) or the fuel pressure accumulator, assuming there is one on this car.

badinstincts

ajajaj, sooo complicated, why cant it just be a simple $10 sensor, lol.
i'm gonna read that vag logging thing now and see if I could determine if there is low fuel pressure before the first try. then see what happens to it after I turn off the engine on the second try. i'll post results soon.