BrianC72gt - Check this out
06-23-2006, 03:44 PM
#1
AudiWorld Super User
Thread Starter
BrianC72gt - Check this out
I printed out the ECU/motronic wiring diagram for an 00, I think that's what you have.
Here is the wiring diagram for the fuel pump and down stream of it:
<img src="http://www.audipages.com/images/ECUwiring2.JPG">
You said you blow a 20 amp fuse during output tests.
I probably jumped the gun earlier, there are three 20 amp fuses powered downstream of the fuel pump relay load side. I gave you the loads for the first one.
First off, I'll throw out a quick check that I might perform before all other troubleshooting.
I know there are O2 sensor and O2 heater wires that pass through the floor board where your car got wet, and they are powered through S3 which is a 20 amp fuse. I can't readily figure out where S3 is physically located by looking at the wiring diagram.
If this is the fuse that is blowing, then I would suspect the wiring connectors for the 02 sensor heaters (maybe the 02 sensor itself?) under the carpet.
Here is my 97, you can see where the 02 sensor goes up through the floor board:
<img src="http://www.audipages.com/Tech_Articles/auto_transmission/transeal8.JPG">
<img src="http://www.audipages.com/Tech_Articles/auto_transmission/transeal9.JPG">
There is a connector under the carpet where they come through.
See if you can find them, disconnect them, and with your old ECU, see if you car will start.
That's the shot in the dark....
If that doesn't work, you'll need to troubleshoot via the diagram above.
NOTES:
Power for the primary of the relay comes from the unswitched 30 bus, through the relay, then to the ECU, Pin 65. The ECU must then switch the fuel pump on when it sees an ignition signal.
Number 1: This is the circuit that I'm suspect of on your car, it continues at trace 109 on page 56/10, you can see how it powers all four O2 sensor heaters, 2 are on that page, 2 are on the next page connected by bus A99.
Report back which fuse you are blowing.
Number 2: This circuit powers the primary of the eight coil packs that fire the spark plugs. It's a 30 amp circuit so I take it that this is not your problem. If this is the case, it shows that there is a good chance that there is nothing flooded or shorted out in the ECU box.
Number 3: Powers the fuel pump directly and only the fuel pump. If this was the circuit that was the problem, it would not be hard to troubleshoot, this is also a 20 amp circuit. You can find the fuel pump motor on page 56/16 trace 183.
Number 4: These are the fuel injection components that I posted about in your previous post:
N208
N205
N156
N261
N80
N145
N144
N112
J299 (see trace 118 from the bottom up)
G70 (mass air flow sensor)
I found it interesting that the old ECU had the air pressure fault code, please post the actual code. I wonder if the new ECU will even go through all of that without being coded to the instrument cluster/immobilizer.
I think you are close.
I got my investment property on the market today and now I have nothing to do!
Well, not really......
Here is the wiring diagram for the fuel pump and down stream of it:
<img src="http://www.audipages.com/images/ECUwiring2.JPG">
You said you blow a 20 amp fuse during output tests.
I probably jumped the gun earlier, there are three 20 amp fuses powered downstream of the fuel pump relay load side. I gave you the loads for the first one.
First off, I'll throw out a quick check that I might perform before all other troubleshooting.
I know there are O2 sensor and O2 heater wires that pass through the floor board where your car got wet, and they are powered through S3 which is a 20 amp fuse. I can't readily figure out where S3 is physically located by looking at the wiring diagram.
If this is the fuse that is blowing, then I would suspect the wiring connectors for the 02 sensor heaters (maybe the 02 sensor itself?) under the carpet.
Here is my 97, you can see where the 02 sensor goes up through the floor board:
<img src="http://www.audipages.com/Tech_Articles/auto_transmission/transeal8.JPG">
<img src="http://www.audipages.com/Tech_Articles/auto_transmission/transeal9.JPG">
There is a connector under the carpet where they come through.
See if you can find them, disconnect them, and with your old ECU, see if you car will start.
That's the shot in the dark....
If that doesn't work, you'll need to troubleshoot via the diagram above.
NOTES:
Power for the primary of the relay comes from the unswitched 30 bus, through the relay, then to the ECU, Pin 65. The ECU must then switch the fuel pump on when it sees an ignition signal.
Number 1: This is the circuit that I'm suspect of on your car, it continues at trace 109 on page 56/10, you can see how it powers all four O2 sensor heaters, 2 are on that page, 2 are on the next page connected by bus A99.
Report back which fuse you are blowing.
Number 2: This circuit powers the primary of the eight coil packs that fire the spark plugs. It's a 30 amp circuit so I take it that this is not your problem. If this is the case, it shows that there is a good chance that there is nothing flooded or shorted out in the ECU box.
Number 3: Powers the fuel pump directly and only the fuel pump. If this was the circuit that was the problem, it would not be hard to troubleshoot, this is also a 20 amp circuit. You can find the fuel pump motor on page 56/16 trace 183.
Number 4: These are the fuel injection components that I posted about in your previous post:
N208
N205
N156
N261
N80
N145
N144
N112
J299 (see trace 118 from the bottom up)
G70 (mass air flow sensor)
I found it interesting that the old ECU had the air pressure fault code, please post the actual code. I wonder if the new ECU will even go through all of that without being coded to the instrument cluster/immobilizer.
I think you are close.
I got my investment property on the market today and now I have nothing to do!
Well, not really......
06-23-2006, 08:26 PM
#2
AudiWorld Senior Member
Re: BrianC72gt - Check this out
Wow, thanks Paul! I pulled the fuel pump feed in the trunk and ran a multimeter on the 12volt feed and ground and all I see is like 2.45 volts regardless of key position....Hmmmmm...the ground back there reads fine.
The O2 sensors were giving me grief but I pulled and dried them long ago. Now what I'm wondering is does the fuel pump harness have a connector below the water line. I suppose I'll pull the rear carpet and find out. Not really a waste of time either as it does need to be properly cleaned and dried. Your notes on the diagram are very helpful. I'm not that proficient with this kind of diagram. I still don't know how to follow the current track number. The fuse that keeps blowing is fuse S1 so I think either the relay is wonky on that one set of contact points...unlikely...or the wiring is in the drink out back. The bummer is I won't get another crack at it until Sunday afternoon....Damn. But is certainly does sound like we've narrowed it down.
I can't tell you how much I appreciate your assistance in reading this diagram.
Cheers,
Brian C.
The O2 sensors were giving me grief but I pulled and dried them long ago. Now what I'm wondering is does the fuel pump harness have a connector below the water line. I suppose I'll pull the rear carpet and find out. Not really a waste of time either as it does need to be properly cleaned and dried. Your notes on the diagram are very helpful. I'm not that proficient with this kind of diagram. I still don't know how to follow the current track number. The fuse that keeps blowing is fuse S1 so I think either the relay is wonky on that one set of contact points...unlikely...or the wiring is in the drink out back. The bummer is I won't get another crack at it until Sunday afternoon....Damn. But is certainly does sound like we've narrowed it down.
I can't tell you how much I appreciate your assistance in reading this diagram.
Cheers,
Brian C.
06-24-2006, 05:49 AM
#3
AudiWorld Super User
Thread Starter
You'll get it
Worse comes to worse, you could run a temporary wire from the fuel pump fuse S1 back to your trunk to get the car going.
Heck, then you could drive it to PA and back and dry the whole car out with the windows open!
To read the Bently diagrams.....
<img src="http://www.audipages.com/images/ECUwiring3.JPG">
1. The power (12 VDC) comes from the top, the "30" line is unswitched power, you can see the battery hooked to it on sheet 56/3.
2. I think 15 is the "load reduction relay" which is switched power, it's all the loads that turn off when the engine is cranking like the headlights, then it picks back up when the ignition switch is turned back to "run".
3. I believe the X bus is switched power, but don't quote me.
4. 31 bus is ground, once again, you can see the negative of the battery connected to the bottom of all the traces connected to it.
HOWEVER, you will normally see the negative connected at the bottom trace. It is shown connected to bus 31 (ground) only on page 56/3. So when you see something tied into the bottom, it's ground.
<img src="http://www.audipages.com/images/ECUwiring2.JPG">
<img src="http://www.audipages.com/images/ECUwiring4.JPG">
To see where S1 goes, you can see that it is fed from the 30 bus, through the fuel pump relay. The hot side has a 2.5 mm gn/ge (green/yellow strip) wire going to it. The load side has a 2.5 mm gn/ro (green/red strip) wire feeding the fuel pump.
Looking at diagram 56/12, you can see fuse S1 is located on trace 137, see the number at the bottom under the ground bus?
Then it stops at a box where my "3" was that I photoshopped in....and it has 183 in the box. This means you go over to trace 183 (you'll find this on page 56/16), and look for a box with 137.
Bingo....you find it, it's the first trace. Notice it's still a 2.5 mm gn/ro wire and it fees G6. Look down at the bottom of the page, and it says G6 is the fuel pump. It then connects to the ground bus.
That's how the fuel pump is getting power.
Heck, then you could drive it to PA and back and dry the whole car out with the windows open!
To read the Bently diagrams.....
<img src="http://www.audipages.com/images/ECUwiring3.JPG">
1. The power (12 VDC) comes from the top, the "30" line is unswitched power, you can see the battery hooked to it on sheet 56/3.
2. I think 15 is the "load reduction relay" which is switched power, it's all the loads that turn off when the engine is cranking like the headlights, then it picks back up when the ignition switch is turned back to "run".
3. I believe the X bus is switched power, but don't quote me.
4. 31 bus is ground, once again, you can see the negative of the battery connected to the bottom of all the traces connected to it.
HOWEVER, you will normally see the negative connected at the bottom trace. It is shown connected to bus 31 (ground) only on page 56/3. So when you see something tied into the bottom, it's ground.
<img src="http://www.audipages.com/images/ECUwiring2.JPG">
<img src="http://www.audipages.com/images/ECUwiring4.JPG">
To see where S1 goes, you can see that it is fed from the 30 bus, through the fuel pump relay. The hot side has a 2.5 mm gn/ge (green/yellow strip) wire going to it. The load side has a 2.5 mm gn/ro (green/red strip) wire feeding the fuel pump.
Looking at diagram 56/12, you can see fuse S1 is located on trace 137, see the number at the bottom under the ground bus?
Then it stops at a box where my "3" was that I photoshopped in....and it has 183 in the box. This means you go over to trace 183 (you'll find this on page 56/16), and look for a box with 137.
Bingo....you find it, it's the first trace. Notice it's still a 2.5 mm gn/ro wire and it fees G6. Look down at the bottom of the page, and it says G6 is the fuel pump. It then connects to the ground bus.
That's how the fuel pump is getting power.
06-24-2006, 06:11 AM
#4
AudiWorld Super User
Thread Starter
Next Step in Troubleshooting
You'll need to figure out why the fuel pump relay has 4.5 VDC on it in the trunk....probably because most of the voltage is shorting to ground along the wire and dropping the voltage.
It's a 2.5 mm (relatively large) wire that is green with a red stripe.
If the fuse is located under the driver's side dash, then I would think the wire goes down the driver's side floor board to the back and through the whole going into the trunk.
Here is one picture I have of the gas tank....it appears that it is routed over to the driver's side.....you can see the 2.5 mm green/red stripe wire....
<img src="http://www.audipages.com/images/gastank1.jpg">
If you <a href="http://www.audipages.com/upgrades/navplusgps.html">go to this page on audipages</a> you'll find how to get the back seat out, etc. but you probably won't need to.
Here is the pass through on the driver's side....I would first trace the fuel pump wire and see if it goes through the driver's or possibly the passenger side:
<img src="http://www.audipages.com/upgrades/nav55.JPG">
I would pull the carpet aside at the door openings and find that wire.....the wiring diagram does not show any connectors.....but it's got to be wet down there and possibly the insulation is comprimised somewhere.
I think once you find it, it will become obvious.
It's pretty easy to pull the carpet back by pulling the trim pieces out at the doors.....you probably don't even have to take the rear seat out, you want to focus on the floor.
Good luck! Once you think you dried it out, check to make sure you have 12 VDC at the green wire in the trunk.....if it's no longer 4.5 VDC....you've probably fixed it.
FIRST THING TO CHECK:
With the key out of the ignition, check the green/red stripe wire in the trunk resistance to ground. Do this by pulling it off the fuel tank connection and check the resistance between it and the brown ground wire.
Normally it would be an open or very high resistance circuit (i.e. 1000K ohms or higher). I think you'll find it's less than 5 oms to ground. This is your problem.
Then pull the carpet, use a hair dryer and dry every inch of the wire, take another resistance reading to ground (you can use the brown wire on the fuel pump connection), and watch it go up....once it's above 1000 ohms (it should be much higher than that), you will have solved your problem.
Or so I think.
It's a 2.5 mm (relatively large) wire that is green with a red stripe.
If the fuse is located under the driver's side dash, then I would think the wire goes down the driver's side floor board to the back and through the whole going into the trunk.
Here is one picture I have of the gas tank....it appears that it is routed over to the driver's side.....you can see the 2.5 mm green/red stripe wire....
<img src="http://www.audipages.com/images/gastank1.jpg">
If you <a href="http://www.audipages.com/upgrades/navplusgps.html">go to this page on audipages</a> you'll find how to get the back seat out, etc. but you probably won't need to.
Here is the pass through on the driver's side....I would first trace the fuel pump wire and see if it goes through the driver's or possibly the passenger side:
<img src="http://www.audipages.com/upgrades/nav55.JPG">
I would pull the carpet aside at the door openings and find that wire.....the wiring diagram does not show any connectors.....but it's got to be wet down there and possibly the insulation is comprimised somewhere.
I think once you find it, it will become obvious.
It's pretty easy to pull the carpet back by pulling the trim pieces out at the doors.....you probably don't even have to take the rear seat out, you want to focus on the floor.
Good luck! Once you think you dried it out, check to make sure you have 12 VDC at the green wire in the trunk.....if it's no longer 4.5 VDC....you've probably fixed it.
FIRST THING TO CHECK:
With the key out of the ignition, check the green/red stripe wire in the trunk resistance to ground. Do this by pulling it off the fuel tank connection and check the resistance between it and the brown ground wire.
Normally it would be an open or very high resistance circuit (i.e. 1000K ohms or higher). I think you'll find it's less than 5 oms to ground. This is your problem.
Then pull the carpet, use a hair dryer and dry every inch of the wire, take another resistance reading to ground (you can use the brown wire on the fuel pump connection), and watch it go up....once it's above 1000 ohms (it should be much higher than that), you will have solved your problem.
Or so I think.
06-24-2006, 07:30 AM
#5
AudiWorld Senior Member
Re: You'll get it
Yup, that is my next step...checking for continuity between the hot feed at the trunk and ground. The reading I was getting at the connector in the trunk was 2.45 volts so the other 10 is going elsewhere. Funny you mentioned the jumper. If I get desparate, that is what I was planning to do...from the back of the relay to the fuel pump. I had most of the diagram figured out it was just those damn boxed numbers and jumps...I didn't know where to go to find the continuation.
I'll try removing the door thresholds to get access, but at this point I also want to pull the interior just to get it clean...wash the carpets with hot soapy water top and bottom and clean the nether regions then dry it out and button it up.
Hey, BTW, you can in fact reach back from the drivers side cylinder head and reach the driver's side cowl drain and pull off that dohickey at the end. It helps if you bleed a little, Ze audi gods require zacrifice. I then managed to fish a long flexible hose up there and blow the hell out of it with the compressor. I've got to get the Detailers attachments for the shop vac or make some to get some suction going from above as I'm reluctant to put more water in this area to blow it out. Water and I are not on speaking terms right now. I'll get over it eventually.
I'll keep you posted.
Brian C.
I'll try removing the door thresholds to get access, but at this point I also want to pull the interior just to get it clean...wash the carpets with hot soapy water top and bottom and clean the nether regions then dry it out and button it up.
Hey, BTW, you can in fact reach back from the drivers side cylinder head and reach the driver's side cowl drain and pull off that dohickey at the end. It helps if you bleed a little, Ze audi gods require zacrifice. I then managed to fish a long flexible hose up there and blow the hell out of it with the compressor. I've got to get the Detailers attachments for the shop vac or make some to get some suction going from above as I'm reluctant to put more water in this area to blow it out. Water and I are not on speaking terms right now. I'll get over it eventually.
I'll keep you posted.
Brian C.
06-24-2006, 07:47 AM
#7
AudiWorld Super User
Thread Starter
Checking resistance to ground
When you check resistance to ground, do it with S1 removed and then again with it installed.
I don't think that will change anything, but if you get a good reading in the trunk with it pulled, the wiring from S1 to the pump is good.
If you get a bad reading with it installed, but not when it is pulled, it's the wiring from the fuel pump relay to the S1 fuse holder.
I don't think that will change anything, but if you get a good reading in the trunk with it pulled, the wiring from S1 to the pump is good.
If you get a bad reading with it installed, but not when it is pulled, it's the wiring from the fuel pump relay to the S1 fuse holder.
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06-24-2006, 09:27 AM
#8
Re: Checking resistance to ground
Paul, I like your annotated wiring diagrams. You could make a business selling overlays for Bentley pages.
Brian, because the 2.45 V is there even with the key off, it is not what's left of 12 V intended for the pump. Instead it's probably leaking in from some unswitched 12 V somewhere. It could be leaking in through the relay socket or panel, the relay, or any of the three fuse's (S1, S2, or S3 in the ST4 fuse block)circuits. It may or or may not relate to what's blowing the fuse, but you will need to eliminate it in order to get accurate resistance-to-ground readings.
Your meter will likely show false resistance readings if used on wires carrying voltage, because the meter measures resistance by determining what remains of a _voltage_ it puts weakly across the probes. Once you make the 2.45 V go away, you can accurately measure resistance.
And it will be useful to measure resistance in the wiring after a fuse that blows. The wiring between the relay and the fuse can't make the fuse blow.
If you're troubleshooting the wire between ST4 S1 and the fuel pump, leave the fuel pump unplugged. (There should of course be infinite resistance between the wire and ground when it's disconnected at the fuse and pump.) Unless you have a spec in the manual to compare against, do not think a low resistance reading across the fuel pump itself is too damning. The resistance across the pump suggests how much current the motor would draw if it was stuck. That will probably be enough to blow a fuse. But once the motor's running, it acts partially like a generator (making "back EMF") which reduces its current draw.
Tom
Brian, because the 2.45 V is there even with the key off, it is not what's left of 12 V intended for the pump. Instead it's probably leaking in from some unswitched 12 V somewhere. It could be leaking in through the relay socket or panel, the relay, or any of the three fuse's (S1, S2, or S3 in the ST4 fuse block)circuits. It may or or may not relate to what's blowing the fuse, but you will need to eliminate it in order to get accurate resistance-to-ground readings.
Your meter will likely show false resistance readings if used on wires carrying voltage, because the meter measures resistance by determining what remains of a _voltage_ it puts weakly across the probes. Once you make the 2.45 V go away, you can accurately measure resistance.
And it will be useful to measure resistance in the wiring after a fuse that blows. The wiring between the relay and the fuse can't make the fuse blow.
If you're troubleshooting the wire between ST4 S1 and the fuel pump, leave the fuel pump unplugged. (There should of course be infinite resistance between the wire and ground when it's disconnected at the fuse and pump.) Unless you have a spec in the manual to compare against, do not think a low resistance reading across the fuel pump itself is too damning. The resistance across the pump suggests how much current the motor would draw if it was stuck. That will probably be enough to blow a fuse. But once the motor's running, it acts partially like a generator (making "back EMF") which reduces its current draw.
Tom
06-24-2006, 10:19 AM
#9
AudiWorld Senior Member
Re: To run the jumper
OK, so I pulled the fuel pump relay and the wiring plugs behind it and the fuel pump fuse. First I found the path from the relay to the fuse ...the hot into the fuse from the relay..all good no resistance in the wire and no continuity to earth from either end. Then I tried the other side of the empty S1 fuse socket and again, no continutiy to earth. So then with the three sockets behind the relay panel unplugged, I made a little jumper with two male blades and a piece of wire...one into constant HOT (red wire) and one out to the fuel pump fuse. Plug the fuse in and...nothing...WTF...Oh, right I had the fuel pump plug unplugged so I test it and see battery voltage. Hmmm interesting... If I plug it in the fuel pump should start pumping maybe I'll even hear a little spark as I plug it in. And then...the sound of silence...no fuel pump. The fuel pump is DEAD. How does a flood kill a fuel pump? No idea.
Just to reassure myself, I'll leave the fuel pump fuse out and re-run all of the output tests to see if everything else does what it should. Somethng doesn't seem right about this. I'm at about an eighth of a tank of gas...would the fuel pump not run if it thought the tank was empty? I've run it lower than what's in it now with no problem. What's bugging me is that wacked out 2.45 voltage reading I was getting last night..maybe I probed the guage feed by mistake? The voltmeter guage is OK, it didn't drop a "1" or anything like that. Puzzling. Is the fuel pump that quiet? Time to open a fuel line and see whats what.
Just to reassure myself, I'll leave the fuel pump fuse out and re-run all of the output tests to see if everything else does what it should. Somethng doesn't seem right about this. I'm at about an eighth of a tank of gas...would the fuel pump not run if it thought the tank was empty? I've run it lower than what's in it now with no problem. What's bugging me is that wacked out 2.45 voltage reading I was getting last night..maybe I probed the guage feed by mistake? The voltmeter guage is OK, it didn't drop a "1" or anything like that. Puzzling. Is the fuel pump that quiet? Time to open a fuel line and see whats what.
06-24-2006, 02:50 PM
#10
AudiWorld Super User
Thread Starter
Tom has good ideas
Yes, most likely the insulation on the power wire for the fuel pump is not comprimised.....more likely a common ground circuit is backfeeding the voltage.
I would try disconnecting the fuel pump at the tank, and take voltage readings from the ground wire to chasis (earth, ground, whatever you want to call it).
It should be zero volts.
Then turn on the ignition.....what happens to the ground voltage? Does it remain at zero or does it go up to some voltage level?
If it does go up to some voltage level, that could be reason why your pump is not running. You need to have 12 VDC across the pump, if the ground wire is back feeding voltage, there will not be a differential, therefore, it won't run.
If it does change significantly (i.e. go up to above 3 VDC), you could always try leaving the fuel pump disconnected, jump the positive with a jumper wire, and jump the negative with another jumper wire to the battery in the trunk.
Or just find ground point 49, see in the drawing below where the fuel pump grounds out? It has a 49 with a circle around it....then look at the text and on the right it says "ground connection near fuel pump". You could always lift the lead there, and jump it directly to the battery with the fuel pump connection made. Take a picture, post it. See if there are other wires grounded to that point. I don't see any in the 56 diagrams, but I bet there are other loads grounded there. If so, they would most likely be the circuits backfeeding voltage.
<img src="http://www.audipages.com/images/ECUwiring4.JPG">
Then see if it starts.
I would try disconnecting the fuel pump at the tank, and take voltage readings from the ground wire to chasis (earth, ground, whatever you want to call it).
It should be zero volts.
Then turn on the ignition.....what happens to the ground voltage? Does it remain at zero or does it go up to some voltage level?
If it does go up to some voltage level, that could be reason why your pump is not running. You need to have 12 VDC across the pump, if the ground wire is back feeding voltage, there will not be a differential, therefore, it won't run.
If it does change significantly (i.e. go up to above 3 VDC), you could always try leaving the fuel pump disconnected, jump the positive with a jumper wire, and jump the negative with another jumper wire to the battery in the trunk.
Or just find ground point 49, see in the drawing below where the fuel pump grounds out? It has a 49 with a circle around it....then look at the text and on the right it says "ground connection near fuel pump". You could always lift the lead there, and jump it directly to the battery with the fuel pump connection made. Take a picture, post it. See if there are other wires grounded to that point. I don't see any in the 56 diagrams, but I bet there are other loads grounded there. If so, they would most likely be the circuits backfeeding voltage.
<img src="http://www.audipages.com/images/ECUwiring4.JPG">
Then see if it starts.
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