pureroundcircle

I have a 99 a4 2.8 quattro, I removed the transmission and replaced the clutch. In doing so some electrical equipment was disconnected and re-connected such as flywheel sensor, o2 sensors, IAT, and transmission plugs. The only thing that is still not connected is the downstream o2 sensors because I need to replace them.

I get everything back togather, and the starter cranks but she wont start. Fuel pump isn't running, and there is no ignition. I checked the fuses, they are all fine. I checked voltage to the fuel pump fuse, only 4v! I plugged in 12v to the right side of the fuel pump fuse and the pump runs. I'm just not sure why i'm not getting power to the ignition or fuel pump, other items in the fuse panel are getting good power. Possibly a relay issue?

Thanks,
Paul

4Driver4

Pull codes, post codes.

pureroundcircle

Well with my OBD2 reader I got a single code the first time I used it, 0102 (Mass air flow), and that was it, I tried starting it a couple more times and tried to read codes again and just get error on my reader. I tried my generic vag-com which was not much help either but it did give this:

18010 - power supply terminal 30 voltage too low p1602-35-10 intermittent

MAF codes is a false code, it wont cause my problems, any idea what terminal 30 is?

I also looked up the fuel pump relay, the service manual says relay 6, but I have a big double relay in position 6, more like a light control thing.

Is there a common relay that turns on the fuel and ignition, or some place I should check voltage before the fuse panel?

Paul

turbo510

"Terminal 30" is VAG's way of saying "this always-hot terminal connects to the battery + post". Many different connections are "Terminal 30". They have other standard ones such as "Terminal 31", which is a ground, "Terminal 15" which is only powered when the ignition switch is ON, etc. Both the fuel pump and ignition depend on the ECU for control, so it there is an interuption of power to the ECU, that could keep the other things from working. Try checking every connection you can find from the battery terminals to the ECU. That small cable on the positive terminal of the battery is a critical one.

pureroundcircle

After a little more work getting my VAG-COM properly set up I got some more codes. I think I know what might be big part of the problem but I still have a question.

New codes:
16706 - Engine Speed Sensor (G28): No Signal
P0322
01367 - Central Locking Pump Run Time Exceeded (Likely Leak)
35-00 - -
01371 - Alarm triggered by Door Contact Switch: Driver's Side
35-00 - -
01370 - Alarm triggered by Interior Monitoring
35-00 - -
01365 - Lock/Unlock Switch: Interior
29-00 - Short to Ground
00956 - Key 2
09-00 - Adaptation Limit Surpassed

I'm pretty sure the problem is the engine speed sensor and not the locking or alarm stuff, I reset the codes from the central locking and they didn't come back. The engine speed sensor probably will cause my no start ignition problem but... Doesn't the fuel pump run when the key is turned on?? before the starter is even cranked?

I also ran though the engine output tests and the fuel pump turns on fine in those tests. Am I wrong in thinking the fuel pump normally primes when the key is turned on or for this car does it not do that and only come on when the key is turned to the starting position?

This weekend i'll pull the rpm sensor and see if I pinched some wires installing the trans, guess I probably should get one on order.

Thanks,
Paul

4Driver4

Suggest you confine your scanning to the ECU.

Concur that crank position sensor is a likely culprit.

Peter Badore

You may have damaged the the engine speed sensor G28 when you changed the clutch. The engine ECU
needs to "see" a speed sensor input before its provides a ground to the relay for the fuel pump.

pureroundcircle

Yes this is the reply I was waiting for! I had a feeling this was probably the case but I just wasn't sure about the fuel pump issue since many cars turn it on when the key is turned regardless.
Thanks.

pureroundcircle

update, finally got a new crank position sesnor, yep that was it, started right up after installing it. Now just to work out all the little stuff like all the broken vacuum lines, audi installs these cheap formed plastic lines and the second they get touched they crumble... There is sooo many of them too.