PDA

View Full Version : A4 will turn over but won't start.... Need help ASAP



Cbotello
12-22-2014, 09:27 PM
My 2000 audi a4 1.8 turns over but won't start .. I pulled my car into my garage to fix a tailight issue I had then when I got done and tried starting it to pull it out it wouldn't start.. I've done a little research on this and it mainly said to replace coolant temp sensor ,so I did and still nothing... How do I test the plugs and coils to se if there still good also i can't seem to hear the fuel pump prime but not sure if they make any noise like other vehicles is there and easy way to check the fuel pump aswell.. Any advice will be greatly appreciated thanks in advance and happy holidays

walky_talky20
12-22-2014, 10:52 PM
I would proceed as follows:

- Make sure ECU is acting ok > Turn key to RUN position (ie: Key on, but engine off). Make sure the Check Engine Light is on SOLID. If good, continue.
- Might just be flooded. Try clear flood mode: Hold gas pedal to the floor, crank starter for 10 seconds, break for 20 seconds. Repeat one or 2 more times. If no change, continue.

- Check for spark > Unbolt the coil from cylinder 1 (nearest radiator). Stuff a spark plug in the end of the coil and holding the opposite end of the plug against the metal valve cover. Have a helper crank the engine. Observe whether spark exists during cranking.

B5A4coastie
12-23-2014, 05:34 AM
Make sure your hand isn't touching the spark plug, hold the top of the coil. I seen a few people shock themselves by not paying attention to what they touch during this process.

Seerlah
12-23-2014, 06:03 AM
Keith, learned the other day de-flood mode does not work on our car. Was testing something for a member when discovered. Engine started and revved to the moon on initial start up (unexpected start). Pretty sure the engine wasn't too happy about that.

Saying he didn't hear the fuel pump prime, I'm going to guy said fuel pump fuse or relay.

walky_talky20
12-23-2014, 06:44 AM
Interesting. I will investigate the clear flood mode. I've used it before on my own car. Seemed to work a treat. But I wasn't, like, watching the fuel spray or trying to actively block a start or what have you. I suppose it's possible the clear flood doesn't fully cut fuel, but just cuts back the fuel some amount.

At least on the DBW cars, the fuel pump does not always prime. So I usually don't pay much attention to that. But if you tap the starter, it should definitely run. Stock pumps usually are too quiet to verify unless you put your ear to the trunk floor and have a helper hit the starter.

Cbotello
12-23-2014, 06:51 AM
How do I test the fuel pump relay and where is that located.... Thank you to all who's replied.

walky_talky20
12-23-2014, 07:41 AM
I wouldn't bother getting at the relay first. Just listen to the fuel pump during (and slightly after) cranking the starter. The access panel is behind the passenger rear seat, on the trunk floor. Just fold down the seat, put your ear the trunk floor, and have somebody hit the starter for 2 or 3 seconds. You should hear the pump "whir" nice and smooth.

If it sounds like it pulsates or has rocks in it, the pump probably faulty.
If you get no noise at all, I would get at the fuel pump connector (green and brown wires as I recall) and make sure you are getting battery power during cranking. Would be best to "back probe" the connector (ie: check for voltage without unplugging anything), but unplugging and checking for power on the harness side is alright too. If you's got's POWAH, but no pump operation, obviously the pump is bad. If you don't have power at the pump, then I would go further up the circuit to find out why. Next stop upstream is the fuel pump relay (well...via the fuel pump fuse of course).

If you wanted to make sure you were on the right track, you could - whilst your hands were on the aforementioned fuel pump connector - *apply 12 volts* to the fuel pump from a battery pack or the cigarette lighter or whatever, then attempt to start the car. If it starts and runs, they you know for certain that your problem is power delivery to the fuel pump. If it doesn't start, then the problem is something else.

Seerlah
12-23-2014, 07:44 AM
^ I have a highly tuned car and not sure if the programming with maestro played a role.

Cbotello
12-23-2014, 08:26 PM
Car has no spark at all and I can not hear fuel pump either wats my next step?

Seerlah
12-23-2014, 08:36 PM
How did you check for spark? You check all your fuses?

Cbotello
12-23-2014, 08:40 PM
Also I just noticed I have always had a check engine light from sai an now it's not on... Does that mean it's the ecu?

walky_talky20
12-23-2014, 08:40 PM
Forget about the fuel for now. Diagnosing the ignition circuit is easier.

- Question asked earlier: Key on and engine off, Do you have a SOLID check engine light? Report.
- Check Fuse #29 for power with key on. Report
- Only if above answers are "Yes, solid" and "Yes, 12 volts at fuse 29", continue:

- Check for spark again. Are you certain that you are missing spark during cranking?
- Unplug the #1 coil. Check pin #1 (Red/Green wire) for 12v+ with key on.
- Check pins #2 and #4 for good quality ground (1 Ohm or less resistance to negative battery terminal).
- Check pin #3 for square wave trigger from ECU during cranking. Use oscilloscope or LED test light only.

You will be missing one of the 4 signals above. That will determine the next steps.

Cbotello
12-23-2014, 08:42 PM
No check engine light

Cbotello
12-23-2014, 08:51 PM
I don't have a multi meter... Is that the only way to check for power to fuse 29

walky_talky20
12-23-2014, 08:53 PM
Okay. ECU is not booting. Possibilities are:

-ECU is not getting power or ground or ignition trigger power
-ECU is faulty

Normal steps would be:
- Quick check of all fuses that power the ECU
- A not uncommon failure that I believe causes the "no CEL" symptoms is a failed ECU Power Supply Relay. If all fuses check out ok, I would probably go after this next:
- Go to relay location
- Check voltage across relay coil (backprobe if possible). If 12v:
- Check source and load contacts for 12v+. Bad relay should have 12v at source, but not load pin.
- Perhaps turn the key on, then smack the relay with a screwdriver handle and see if the CEL comes on. Enjoy hero status for making that crap happen.

If 0 volts:
- ECU Power Supply relay is not getting trigger to turn on from the ECU.
- Check at ECU connector for all power, ground, and ignition trigger.
- If none are missing, ECU is faulty. If it's a chipped ECU, it's likely failure of the hasty internal solder work pursuant to the chip addition.

Cbotello
12-23-2014, 09:28 PM
I do have other dash light on like airbag and abs would those be on even with a bad ecu

walky_talky20
12-24-2014, 05:51 AM
Yes. ABS and Airbag are separate computers and have individual control of their own lights.

Cbotello
12-24-2014, 03:10 PM
Will a passat ecu work on my a4 it is also a atw 5spd

walky_talky20
12-24-2014, 08:01 PM
Yes, Passat ECU's interchange. 2000 is a very specific year, so make sure the part number matches. I think it will end in 018P (zero-one-eight-Papa-over).

But ECU failure is rare, especially if the ECU has not been modified internally. Until proven otherwise, I would be more suspect of literally everything else. Relay, wiring, ignition switch signal, current phase of the moon, etc. And I definitely would not be buying parts until I had a solid diagnosis.

thedownwardsprl
12-26-2014, 04:33 AM
Pump relay?

walky_talky20
12-26-2014, 08:17 AM
Fuel Pump Relay possibilities were discussed in post 4, 6 and 7.

OP has verified no spark, for which a failure of the Fuel Pump Relay cannot cause.