Mike_k

This is driving me nuts... So I pulled both pumps and replaced both. In doing this, I noticed that the small plug on the passenger side pump had the insulation chewed off it's wires and they were shorted out. This was the smaller of the two harnesses with only two wires going to it. I'm not sure what function this harness serves but I know it's not pump power.

There was a nest of some sort over the driver's side pump so I figure it's a mouse that's responsible for this. Whatever it was, it looks like it's been shorted like that for awhile. Perhaps it's the passenger side sending unit? Any takers on that one?

Here's what's really got me upset though... I can find a fuse for the right side fuel pump but there's no corresponding fuse for the driver's side fuel pump. Double You Tee Eff... How does that happen? Where is that fuse?

The problem persists though. Turn the car on and it runs for 30 seconds exactly at which point it starts chugging and then stalls.

Mike_k

Disregard... I brainfarted and thought I replaced the passenger pump when I didn't. Replaced that and it runs like a champ. So S4master, this is your first documented passenger side failure. :-)

That said, I snagged that wire that was chewed through. It's not plugged in and the car is running fine. Obviously since it was chewed though well before the pump failed. The question of the day is what is it? There are three plugs coming out of each side...

One is for the pump and one is for the level sensor. What is the third?

rn3037

Old thread and sorry to jump in but I have a fuel pump/fuel supply question, I have lean codes and my measuring block 107 Fuel Supply System always fails so I am wondering if one faulty pump could be causing this:

I can't get rid of codes P1136 & P1138 - System Too Lean (add)

Here is a list of stuff I replaced/checked.

-New O2's
-New Coolant Temp Sensor
-New MAF & swapped known good MAF
-New Fuel Filter
-New PCV Valve
-Checked for vacuum leaks
-Swapped good Evap Valve
-Plugged off Secondary Air Injection vacuum lines to eliminate the possibility of leaking SAI pump

The thing I notice in my logs is that usually on a cold start, the car will add 10-14% fuel in both banks but once it warms up fully it only adds 3-4% and it's also negative at times.

LOG
https://docs.google.com/spreadsheet/...=sharing#gid=0

BLOCK 107 BASIC SETTING (System Not Ok)
Any idea what causes this to fail? Whenever I test, it always goes to 25% fuel and fails. The strange thing is that I unplugged the MAF and it passed.



***UNPLUGGED MAF*** How come the Fuel Supply System is "OK" when I unplug the MAF? I also notice that my fuel trims are perfectly within spec all the time with the MAF unplugged. The MAF can't be the problem because I tried a new one as well as one from a good car.

mishar

When you unplug MAF it goes to a limp mode enriching the mixture. So there is enough fuel to do that. Also if the fuel pump (right) doesn't have enough flow/pressure on idle it wouldn't run at all on a higher rpm's. It looks like you have an air leak after MAF. Try running test without air filter. If a leak is between MAF and throttle body that should make a difference. It could be somewhere on the intake manifold. Cleaning injectors may help too. Check MAF harness carefully too.

rn3037

Thanks for the expertise Mishar! I will take a look at the fuel trims without the air filter on.

See I tested the vacuum at idle and it's around 16-17 inches of mercury which I think is ok, if there was a huge vacuum leak I would imagine the fuel trims would always be adding 10-15% but once the car is warm the trims look normal.

mishar

Not really "expertise". More like a brainstorming.

rn3037

That's all we can do! Eliminate variables.

One other point to note, whenever I reset the check engine codes via Vag Com, the fuel trims max out at 25-27% automatically. I did the same thing on my 2006 A8L (has no issues) and the fuel trims stay within normal spec. Wondering if this behavior is telling us something, possible ECU issue?

mishar

May be, but I don't think so. It is more of analog thing. I wouldn't expect digital logic to be half broken.

jakematic

I'm beginning to wonder about that as well.

When in group 107 with the MAF plugged in, try wiggling / twisting wire to see if Lambda's change or use an overlay harness.

I would expect the trims to go to zero immediately after clearing DTC...

mishar

Yeah, but it goes much better with beer.