2005 Jetta fuel filter & fuel pump issues - seeking advice

mvoss15

Well-known member
Joined
Jul 31, 2005
Location
Indiana
TDI
2014 Audi Q7 TDI, 2015 Golf Sportwagen TDI (previous 05 Jetta TDI, 09 JSW TDI, 05 Jeep Liberty CRD)
I'm looking for some advice - just spent the last 2 hours tonight reading every post I could find on here that seemed to be related to my current issue. Actually, I think there are two issues. Here's the story:
Last Saturday, I went to change my fuel filter. My car is a 2005 Jetta TDI with a PD engine - and early 05 - older body style. I followed my normal procedure, and once everything was hooked up (yes, I replaced the o-rings), I took my handheld vacuum pump connected to the outlet of the filter and attempted to prime the filter. Thing is, however, I could not build up any vacuum - it was like air was somehow leaking into the filter. Just to make sure all was well, I connected my pump directly to the fuel line coming from the tank, and it pulled fuel up just fine. Assuming that my filter must have had a bad seal or something, I put my old filter back on, until I was able to get a a replacement.
So, tonight, I took a second fuel filter, and had the same symptoms. I simply could not prime the filter - I cannot build up any vacuum pressure to pull fuel in. I ended up filling the filter with fresh fuel through the top of the filter (where the T-fitting connects), and then was able to pull fuel through with my vacuum pump, though there seems to be air getting in. Hopefully it will get me to work OK in the morning!
So, first issue: looking for advice - think I have a bad o-ring (I've replaced them twice however), is the t-fitting bad, or something else? Am I risking anything major if there is an air leak if i drive it for a while to see what happens? I read a tip in one post about putting Vaseline on the o-rings - is that advisable?
Ok, now the second issue: in my many attempts to prime the filter, I remembered reading that I should be able to use the lift pump in the fuel tank to do the job. I tried the key-on, wait, key off routine many times, but noticed that I really could not hear any noise from under the backseat. So, for fun, I disconnected the fuel line going into the fuel filter again, wrapped it in a rag, and tried the on-off a few more times. No fuel was coming out. So, it seems that my in-tank lift pump has gone bad. My hunch is that it has not been working for a long time, as I don't ever recall being able to hear a noise from under the back seat. Funny thing, however, is that the car seems to be running just fine without it. Most of the posts I've read about here that refer to lift pump failure talk about the car simply not running - mine's not had any issues.
So, second issue: is it likely that my lift pump has failed? Was my "test" a valid test of the lift pump? Any other suggestions here? And how come my car is running fine, if it in fact has failed? I'm assuming that the pumps in the engine are probably working over-time in order to make up for this?
Any suggestions, advice, alternate theories, etc. would be appreciated. And, if I get stranded on the side of the road on my way to work tomorrow (50 mile commute), I think I'll know why :)
 

myke_w

Vendor
Joined
Jan 30, 2003
Location
Cbus, Ohio
TDI
03 TDI Wagon
If no fuel is coming out with the key on and the inlet hose off the filter, then either the fuel pump fuse is blown or the pump is bad. You could also check for power at the pump witha test light and a helper after verifying the fuse is good to rule a bad connection out.

If you need a new one - I can help you out ;)
 

2004STARWARSTDI

Top Post Dawg
Joined
Oct 19, 2004
Location
LAKELAND, FL
TDI
2004 Platinum Gray GLS Jetta / 2006 Silver Jetta with DSG
In tank fuel pump

Your theory is wrong about in tank fuel pump. If the fuel pump is not working then the car will not run! No fuel No start!:eek:
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
PD lift pump operation and failure modes

I have read, on this site, of folks having different results when their lift pumps fail.
Some get zero fuel flow, and can draw a very hard vacuum on the fuel line and still get zero fuel flow. Their car dies and will not run.

Others car's will still run, perhaps starving for fuel at high loads, perhaps not. It may take a bit of extra cranking to get started.

Why the difference? I sure would like to know. Maybe different failure modes?

Update: I think I have found out why results vary. Please read post http://forums.tdiclub.com/showthread.php?t=225672 .

If your in tank lift pump fails, and you have an air leak in a fuel line, your car will not run (just as an ALH would not run with an air leak in a fuel line.)

If your in tank lift pump fails and the eductor jet is plugged or your fuel inlet screen is plugged, then you can get no power.


What we know for sure is that your pump should run when the key is turned on (at least my early 05 does) and that it should fill the filter, lines and provide plenty of flow.

You can check your fuse (number 28?), check for power to your pump, run a 12 volt jumper wire to your pump and see if it will run. Just do some old-fashioned trouble shooting. You can probably find out why it is not working.
 
Last edited:

mvoss15

Well-known member
Joined
Jul 31, 2005
Location
Indiana
TDI
2014 Audi Q7 TDI, 2015 Golf Sportwagen TDI (previous 05 Jetta TDI, 09 JSW TDI, 05 Jeep Liberty CRD)
Disconnected the power connections to the fuel pump, hooked up a multimeter - the pump is getting power, so the electrical connection and the fuse seem to be fine.
My car has no problem starting or running, even under heavy load. I haven't noticed any major change between how the car runs now (currently at 102,000 miles) from when I bought it new. I don't know much about the design of the in-tank pump, but could there be any possibility that for some people it stops working in a "closed" position, and for others in an "open" position? Regardless, if the in-tank pump isn't working, I'd assuming that not replacing it would likely cause undue stress on the tandem pump.
Just for fun, tomorrow I'll test it again by disconnecting the supply line from the fuel filter again, to see if I get any fuel flow when I turn the key to the on position.
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
The lift pump only runs for a second or two at "key on". It then runs continuously while the engine is running. So you may have to cycle your key a few times.

I ran a hot wire and ground to my pump, in order to pump out the tank for gauge calibration. I was careful to monitor it closely and secure the pump at the first sign of flow decrease.

Remember there are two hot sources to your pump connector, one is the fuel gauge power to the resistor, and the other is the power to the pump. IIRC the outer two connections of the four were for the pump. One hot, one ground. The inner two connections were for the gauge, and would have power continuously witht the key on. The hot outer connection for the pump will only have power for a second or two for each key cycle. Check your bentley or PM me, and I will check for you. Gotta go, now.

DanG
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
PD lift pump operation and failure modes

This is a re-post of an updated earlier post.

I have read, on this site, of folks having different results when their lift pumps fail.
Some get zero fuel flow, and can draw a very hard vacuum on the fuel line and still get zero fuel flow. Their car dies and will not run.

Others car's will still run, perhaps starving for fuel at high loads, perhaps not. It may take a bit of extra cranking to get started.

Why the difference? I sure would like to know. Maybe different failure modes?

Update: I think I have found out why results vary. Please read post http://forums.tdiclub.com/showthread.php?t=225672 .

If your in tank lift pump fails, and you have an air leak in a fuel line, your car will not run (just as an ALH would not run with an air leak in a fuel line.)

If your in tank lift pump fails and the eductor jet is plugged or your fuel inlet screen is plugged, then you can get no power.


What we know for sure is that your pump should run when the key is turned on (at least my early 05 does) and that it should fill the filter, lines and provide plenty of flow.

You can check your fuse (number 28?), check for power to your pump, run a 12 volt jumper wire to your pump and see if it will run. Just do some old-fashioned trouble shooting. You can probably find out why it is not working.
 
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