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Discussion Starter #1
Vehicle:
2004 VW Touareg V8

Back Story Cliff Notes: Wife was on E, Put in 8 gallons. Car immediately started stumbling, and eventually died and would not stay running for more than 20 or so seconds. Towed it home. This morning it will not start at all, not even momentarily, it tries to, as a few cylinders will fire off, but not fully start.

Question:

What voltages should I expect to see and for how long from the Tank connector Pairs?

Where I am currently at:

I cut the carpet and popped the cover off the Passenger Side Pump (right) and hooked up a multi-meter.

When opening the door or turning the key, the two outside pins (larger gauge wire) show ~10v BUT only for about 5 seconds or so. Should this stay energized longer?

When opening the door or turning the key, the two inside pins (smaller diameter) show only about 1.5v

Is what I am seeing normal? I am trying to hunt down the root cause rather than just needlessly tossing money at it.

Pic For Clicks:

Passenger Pump, testing inside pins. Also plan on cleaning this up as I hate any kind of corrosion.




I saw this post in THE fuel pump thread:

New, before you do anything.. check the wire harness that connects to the pumps, make sure you are getting at least 11.5V power to them. At this point im only getting 1.5 reason why the pumps are turning on and the car does not start. I checked all the fuses and swapped all the relays but all seem fine.... anyone has another idea what to check for next?
But wasnt sure if he was getting 1.5 on both pairs of pins, or just the center, or what pump he was testing. If 1.5v is NOT normal for the center pins, or the duration of energization is not normal, and it mat just be the sending unit at fault, that would be good to know.

Any help is appreciated, thank you!
 

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Discussion Starter #2
Update:

I cut the carpet and popped the cover off the Driver Side Pump (left) and hooked up a multi-meter.

When opening the door the two outside pins (larger gauge wire) remain at Zero volts
When cranking the engine, they show ~10v for as long as the engine attempts to crank

When opening the door the two inside pins (smaller gauge wire) remain at 1.5 volts constantly
When cranking the engine, they show 0v for as long as the engine attempts to crank.

Is what I am seeing normal? I am trying to hunt down the root cause rather than just needlessly tossing money at it.


When Pulling 404 Relay:

Passenger Side Pins stay at 0v in all condition
Driver Side acts as described above, no noticeable change
 

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Discussion Starter #3
I will keep talking to myself lol:

Made a pair of jumper leads, and tested each pump by placing the leads on the outside pins, and powering them via a battery charger. I tested each pump individually, and both started humming, and the multimeter was showing about 10 volts... (its a pretty old 10amp battery charger)

I could have sworn I was not hearing the humming when the pumped were plugged into their respective harnesses. The driver pump is pretty audible when hooked up to the battery charger. I am really at a loss on this one.

I was going to try starting the car with the pump being directly driven by the battery charger, but the battery is getting a little weak from all the testing so I have it charging right now.

I have a filter/sender unit coming. So I will try that first to see if anything changes I guess, unless all this points to something else going on.
 

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Had to laugh at the back story: "Wife was on E" - which I misread as shorthand for Ecstasy!

Only sorry I can't help on the pumps.

Keep on taking the pills and talking to yourself . . . !
 

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Discussion Starter #5
/\ /\ HAHA If she was filling the tank while on Ecstacy I would at least have a better understanding for why the vehicle wont start. :giggle:
 

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Can you drive the fuel pumps manually with VCDS? I've never looked into it, but I suspect it's possible.

That would tell you if the fuel pump controller is working or not working.
 

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Discussion Starter #7
Can you drive the fuel pumps manually with VCDS? I've never looked into it, but I suspect it's possible.

That would tell you if the fuel pump controller is working or not working.

Hmmm, thats a good idea. I wonder what output module its listed as in the output test.


Update:

I made a second set of jumper wires so I could run both fuel tanks at once off the battery charger, with direct 12v input (both pumps hummed to life). When I did this the car would resist starting, but would run for a few seconds (5 or so) before stumbling and dying. Restarting would yield the same result. The multimeter was showing 9.5v for the power source.

Applying any throttle input would instantly kill it.I am wondering if maybe the filter is finished?

running either of the pumps manually on their own, the vehicle would not start

Running both pumps simultaneously would result in a sputtered start, brief idle, and eventual death.

I tried running one pump hooked up to the OEM connector and the other running off the battery charger and the vehicle would try harder to start but couldn't fully get an idel going enough for the starter to disengage.
 

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Maybe see if there is a line you can disconnect, post pump, and direct it to a bucket of some sort. Turn key and see if pump primes at all...? Same thing in starting to crank... see what kind of pressure comes from the exposed line.

I'm guessing if its a dribble, you have a dead pump. If its a fire hose, then the pump is good and maybe a clogged filter...?

How about a schrader valve on the manifold? Cheap tester at Harbor Freight to test pressure at the manifold...?
 

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Hmmm, thats a good idea. I wonder what output module its listed as in the output test.

Update:

I made a second set of jumper wires so I could run both fuel tanks at once off the battery charger, with direct 12v input (both pumps hummed to life). When I did this the car would resist starting, but would run for a few seconds (5 or so) before stumbling and dying. Restarting would yield the same result. The multimeter was showing 9.5v for the power source.

Applying any throttle input would instantly kill it.I am wondering if maybe the filter is finished?

running either of the pumps manually on their own, the vehicle would not start

Running both pumps simultaneously would result in a sputtered start, brief idle, and eventual death.

I tried running one pump hooked up to the OEM connector and the other running off the battery charger and the vehicle would try harder to start but couldn't fully get an idel going enough for the starter to disengage.
Doubt you will ever start/ run the car in this manner, ever The fuel pump priming is tied to entry authorization and control for the car that begins when you open the drivers door and signals are sent to the relay to start priming function.

The suction pumps can make all kinds of noise when powered, does not mean they are ok or providing adequate flow.

My bet is the priming pump behind drivers seat is shot. The filter assembly above the pump may need replacing or filter replaced too.

For the priming pump believe connection between terminal 3 & 4 of the plug should read 11.5v with ignition on. On the other side think it is terminal 1&2. Best way to check pumps is flow. Should get about 800cm with 15 seconds of flow.
 

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Discussion Starter #10
My bet is the priming pump behind drivers seat is shot. The filter assembly above the pump may need replacing or filter replaced too.

For the priming pump believe connection between terminal 3 & 4 of the plug should read 11.5v with ignition on. On the other side think it is terminal 1&2. Best way to check pumps is flow. Should get about 800cm with 15 seconds of flow.
I am not sure if its a v8 vs v6 thing, but my priming pump is on the passenger (right hand) side. At least via what I witnessed from my tests above with the multimeter. (as that one displayed voltage at the connector when opening the door)

Also, thank you for your reply. Today I took some 3/8" I.D. tubing and connected it to the fuel outlet behind the passenger seat. I then had an old bottle with milliliter increments on it. I manually ran each pump via the jumper leads and the battery charger.

The fuel did not have its usual blue tint that I would have expected from premium fuel, and was even a bit cloudy at first.

The Pump with the filter housing behind the driver seat put out about 800ml in about 15 seconds.

I then switched over to the leads for the pump behind the passenger seat... it was pathetic. It took almost over a full minute to reach the 800ml mark.

So it looks like the pump behind the passenger seat is failing hard. I tried jumping the relay for the main pump (the good one behind the drivers seat) to see if I could get the touareg to fire off. It at least made an attempt, but the battery was again pretty low.

So it looks like I will be replacing the passenger pump and tossing in the new fuel filter while I am in there. The driver pump seems to be operating as it should, so I do not see any reason to replace it at this time.
 

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I am not sure if its a v8 vs v6 thing, but my priming pump is on the passenger (right hand) side. At least via what I witnessed from my tests above with the multimeter. (as that one displayed voltage at the connector when opening the door)

Also, thank you for your reply. Today I took some 3/8" I.D. tubing and connected it to the fuel outlet behind the passenger seat. I then had an old bottle with milliliter increments on it. I manually ran each pump via the jumper leads and the battery charger.

The fuel did not have its usual blue tint that I would have expected from premium fuel, and was even a bit cloudy at first.

The Pump with the filter housing behind the driver seat put out about 800ml in about 15 seconds.

I then switched over to the leads for the pump behind the passenger seat... it was pathetic. It took almost over a full minute to reach the 800ml mark.

So it looks like the pump behind the passenger seat is failing hard. I tried jumping the relay for the main pump (the good one behind the drivers seat) to see if I could get the touareg to fire off. It at least made an attempt, but the battery was again pretty low.

So it looks like I will be replacing the passenger pump and tossing in the new fuel filter while I am in there. The driver pump seems to be operating as it should, so I do not see any reason to replace it at this time.
Don't think there is a difference v6/v8. The priming pump is in the larger side of the fuel tank and below the filter flange assembly. The passenger pump is in the smaller side of the fuel tank below the pressure regulator assembly. The priming pump is also a transfer pump moving fuel from larger side of fuel tank to smaller side as the pump behind the passenger seat is what runs the car after initial start up. From your first post car ran for about 20 seconds than stalled because the passenger side pump did not take over as designed. Must have misread initially, sorry for wrong response.
 

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Discussion Starter #12
When dealing with VW engineering, there is NEVER a wrong response haha

After reading the long fuel pump thread here:
http://www.clubtouareg.com/forums/f43/stall-around-30-seconds-fuel-pump-43583.html

It seems like people were having different results for which one the priming pump was, and some were guessing it was a v6 vs v8 thing, so I was only making that statement based off that.

However, during my own voltage tests with a multimeter the passenger pump (right hand side) was the only one to receive temporary voltage once the driver door was opened, while the driver side pump remained at 0v.

After getting the vehicle home, it would no longer fully start, or stay running for more than a matter of seconds.

Maybe its a difference of production year or a sign of something else going on (maybe a bad 404 relay would display these symptoms?), because I am not sure why my 2004 V8 uses the passenger side as a priming pump, when so many others seem to observe the opposite.

I have a new passenger pump coming today, so I hope to install that along with the new filter tomorrow.

I REALLY appreciate the replies and input!


Here is a fun little tank cutaway pic I came across, just thought I would share:

 

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When dealing with VW engineering, there is NEVER a wrong response haha

After reading the long fuel pump thread here:
http://www.clubtouareg.com/forums/f43/stall-around-30-seconds-fuel-pump-43583.html

It seems like people were having different results for which one the priming pump was, and some were guessing it was a v6 vs v8 thing, so I was only making that statement based off that.

However, during my own voltage tests with a multimeter the passenger pump (right hand side) was the only one to receive temporary voltage once the driver door was opened, while the driver side pump remained at 0v.

After getting the vehicle home, it would no longer fully start, or stay running for more than a matter of seconds.

Maybe its a difference of production year or a sign of something else going on (maybe a bad 404 relay would display these symptoms?), because I am not sure why my 2004 V8 uses the passenger side as a priming pump, when so many others seem to observe the opposite.

I have a new passenger pump coming today, so I hope to install that along with the new filter tomorrow.

I REALLY appreciate the replies and input!

Here is a fun little tank cutaway pic I came across, just thought I would share:
Great picture of tank cutaway.

The whole system is over engineered if you ask me. Easiest way to tell on the priming is have the back bench up with carpet off the access panels and hear which pump activates when you open the drivers door. That's the priming pump. I can hear my pump prime whenever I open the drivers door. When I first got the car thought my seat was readjusting.
 

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/\ Agreed, It seems like half of those tank hoses could have been eliminated if they put the fuel filter and fuel outlet on the same side.

So I got everything swapped over yesterday. What a pain in the butt trying to fish all of those hoses from one tank to another. I tried making marks to keep everything straight, but of course they washed right off haha

This video was a big help:


I also took pictures of how everything sat in the tank to ensure when I buttoned it up, everything would be where it was before and out of the way.

So after swapping the fuel sending unit, and the passenger pump, along with tossing in some new tank gaskets, I gave her a go.....

NOTHING, same as before... uhg... Tried it a few times, same result.

I unplugged the MAF and held the throttle open for a big, then tried again. It stumbled to life but would die after a few seconds. This kept happening...

Crud, Replugged in the maf, tried again... same thing.

I pulled out two of the spark plugs and they were wet, but had what looked like droplets of condensation on them.

Remembering that the gas I pumped out during the fuel pump flow tests looked odd, I finally decided to try it with fresh gas (keeping in mind all of this happened right after putting ~8 gallons in when the car was on E).

So I disconnected the fuel outlet line (this time there was lots of pressure, where before almost non-would come out, so that a good start) Put my 3/8" I.D. Hose on the fitting, and tried starting just to verify fuel was flowing during starts, it was.

Then hooked my jumper leads up directly to the battery charger and pumped out as much fuel as I could.

The tank guage was now reading between E-1/4. Ran to a brand new gas station, picked up 5 gallons of 92, went home and filled her up with that.

Retried to start her... BINGO. It fired up on the second try, but was running rough.

Hooked up VagCom and went to measuring blocks 15, 15, and 17 to view cylinder misfires. 4 and 8 were climbing rapidly!!! 100+ woah

Swapped coil Packs, still 4 and 8. Swapped spark plugs, still 4 and 8.

The plugs didnt look great anyway, so I swapped in some new NGK Iradium plugs (the old ones smelled a bit funky). Still after a few seconds rapid misfires on 4 and 8, but only at idle, off idle they ran fine.

Being the two rear cylinders I figured they must have something in common, maybe the injectors are to blame and something happened as a result of the crap fuel (moisture or something).

Sooo I decided that the following day i would swap injectors to see if the misfire followed, but before that i figured, well it runs great when not at idle, lets just see if i can burn it off. I went railing around for a bit with Vagcom still displaying measuring blocks 15-17. After a few blocks the misfires decreased at idle, until after about 5 minutes they were gone completely (1 or two would occasionally register but 1-3 is fairly normal as long as its not consistent). Yay!!!

So it appears it was mainly bad gas, the weak fuel pump wasnt helping at all either, but today I am going to fill her up with non-ethanol 92 to dilute the remaining crap gas even further, toss in something like gumout just for good measure, and call it a day. I have NEVER had bad gas from a gas station in my life, and thought it was mainly just a cop out excuse when people couldnt figure out what was really wrong haha now I know better.

Now, that is pending it still starts this morning haha fingers crossed
 

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That's a great reference video! Here's their other one showing the filter change, apparently its separate and serviceable. Yet they install a full new cap N filter combo.

 

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That's a great reference video! Here's their other one showing the filter change, apparently its separate and serviceable. Yet they install a full new cap N filter ..
That video was another huge help when researching what to expect!

In the comments of that video, edge motorsports (the video's creator) says they have changed their position on separating the sender to replace just the filter, so they must have run into some issues doing it that way with performance, as they now will only replace the entire unit. Maybe there were sealing or flow issues.
 

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Ah that's sounds plausible. I didn't look at the comments but I watched both of the videos.

I kept thinking to myself that would be something I would rather pay someone to do... But would I trust them or want to pay absurdly? Not really!

I wonder if we should start replacing the top filter half around 60-80k miles, so we don't strain the pump.
 

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/\ Agreed, It seems like half of those tank hoses could have been eliminated if they put the fuel filter and fuel outlet on the same side.

So I got everything swapped over yesterday. What a pain in the butt trying to fish all of those hoses from one tank to another. I tried making marks to keep everything straight, but of course they washed right off haha

This video was a big help:

Video Link: https://www.youtube.com/watch?v=fyNOvhwtCdk

I also took pictures of how everything sat in the tank to ensure when I buttoned it up, everything would be where it was before and out of the way.

So after swapping the fuel sending unit, and the passenger pump, along with tossing in some new tank gaskets, I gave her a go.....

NOTHING, same as before... uhg... Tried it a few times, same result.

I unplugged the MAF and held the throttle open for a big, then tried again. It stumbled to life but would die after a few seconds. This kept happening...

Crud, Replugged in the maf, tried again... same thing.

I pulled out two of the spark plugs and they were wet, but had what looked like droplets of condensation on them.

Remembering that the gas I pumped out during the fuel pump flow tests looked odd, I finally decided to try it with fresh gas (keeping in mind all of this happened right after putting ~8 gallons in when the car was on E).

So I disconnected the fuel outlet line (this time there was lots of pressure, where before almost non-would come out, so that a good start) Put my 3/8" I.D. Hose on the fitting, and tried starting just to verify fuel was flowing during starts, it was.

Then hooked my jumper leads up directly to the battery charger and pumped out as much fuel as I could.

The tank guage was now reading between E-1/4. Ran to a brand new gas station, picked up 5 gallons of 92, went home and filled her up with that.

Retried to start her... BINGO. It fired up on the second try, but was running rough.

Hooked up VagCom and went to measuring blocks 15, 15, and 17 to view cylinder misfires. 4 and 8 were climbing rapidly!!! 100+ woah

Swapped coil Packs, still 4 and 8. Swapped spark plugs, still 4 and 8.

The plugs didnt look great anyway, so I swapped in some new NGK Iradium plugs (the old ones smelled a bit funky). Still after a few seconds rapid misfires on 4 and 8, but only at idle, off idle they ran fine.

Being the two rear cylinders I figured they must have something in common, maybe the injectors are to blame and something happened as a result of the crap fuel (moisture or something).

Sooo I decided that the following day i would swap injectors to see if the misfire followed, but before that i figured, well it runs great when not at idle, lets just see if i can burn it off. I went railing around for a bit with Vagcom still displaying measuring blocks 15-17. After a few blocks the misfires decreased at idle, until after about 5 minutes they were gone completely (1 or two would occasionally register but 1-3 is fairly normal as long as its not consistent). Yay!!!

So it appears it was mainly bad gas, the weak fuel pump wasnt helping at all either, but today I am going to fill her up with non-ethanol 92 to dilute the remaining crap gas even further, toss in something like gumout just for good measure, and call it a day. I have NEVER had bad gas from a gas station in my life, and thought it was mainly just a cop out excuse when people couldnt figure out what was really wrong haha now I know better.

Now, that is pending it still starts this morning haha fingers crossed
Not certain how the ignition coils are wired on the 8 but on the 6, they are wired in pairs spliced into the harness so a problem in one cylinder may cause a problem with it's pair. The signal wires are separate ( very thin wire) and home run to the ECU. Hope the fuel and pump squares you up.
 

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Discussion Starter #19
I wonder if we should start replacing the top filter half around 60-80k miles, so we don't strain the pump.
I am starting to think that is a good idea. I guess I didnt NEED to replace mine, as the main pump seemed to be flowing the correct volume anyway, but messing with all those hoses is not fun, so I would like to delay doing it again for as long as possible, so I swapped it out.

Some people report better gas mileage when running a new filter, whether that's true or not who knows, but it couldn't hurt with these big V8s :D

And like you mentioned, Its easier to swap the filter housing than it is to swap pumps that go dead from extra strain (and cheaper too lol)

I had a 50/50 mix in the tank this morning of old crap gas (what i couldnt get out of the tank manually the day before) and new 92 gas, of about 7 gallons total combined.

The idle seemed lower and closer to 500-550rpm and still had a slight vibration when at idle, but not enough to trigger the CEL. So I put in some GUMOUT additive to supposedly help remove moisture (figured it couldnt hurt), and put in 14 gallons of pure fresh 92 without ethanol. After that and blasting down the road the car was infinitely better. No more lumpy idle, smooth as a purring kitten. noticed the idle was a bit higher now at ~650rpm

So far so good *knock on wood*

I might contact the station owner to see if anything can be done to help compensate for this issue(figure its worth a shot). I saved some of the gas I took out. Not sure if there is an easy way to test it, but would be curious to see the results.
 

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Discussion Starter #20
Just wanted to update for anyone else who may find themselves in a similar boat: So far so good, still running strong. \\:D/
 
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