Fuel Pump Issues

[canonball]

Hey guys, I did some searching and found some helpful info but I'm still not exactly sure whats going on the car and just want to get some insight before I start yanking things out and throwing parts at it. First off, I've got an '05 A4 1.8t 6mt, 132,xxx miles on the clock. I always for get that.

So several days ago my car started making a loud-ish humming noise, like loud enough that I could just hear it with the music on and it seemed intermittent. I had a feeling it was the fuel pump because of the kind of sound and also that it was coming from the rear of the car. So, yesterday I'm driving to work and it sputtered for a min and I was about to pull off into the emergency lane when it stopped and was driving fine again. So I continued on, got several miles down the road and it sputtered again but the engine cut out this time. I pulled over, tried starting it again and it would solidly crank but wouldn't start at all. The best I could get is getting it to run for like 2 seconds before it cut off again and ended up having it towed home.

I'm suspecting it's fuel pump related and I'm not very familiar with these german fuel pumps, I'm used to Hondas that have just the fuel pump, like a walbro, not the whole basket, sending unit, etc. so I'm trying to learn more about it and how it works. I'm tempted to go ahead and order a fuel pump assembly and replace it. Any thoughts on this? Suggestions? I know some people have checked/tested the relay and continuity to the pump. Not super confident with a multi-meter but I have one and could try it.

Also, has anyone had luck with getting fuel pump items from generic stores like Autozone or O'reilys? Or better to get from ECS or FCP?

[Puddin Tane]

Your pump is most likely VDO/Continental brand if original. That's what I'd go with, nothing cheaper. Exact same thing as Genuine minus the $200+ markup just to have four effing in-line rings molded into the plastic. Europaparts.com is also good and has a better price than the two you named, except FCP lifetime warrants everything... If the local parts dealers can beat their price, great, but be sure you're getting the VDO/Conti pump.

As for determining if the pump is your problem, others here are more expert. One thing to try tho is yanking the rear seat and opening the lid underneath on the passenger side, then aiming your ears that way while turning the ignition just to run, not start. The pump will audibly switch on if working. If so, see if it will start and if the humming is louder through that open hatch.

If you do replace the pump, also replace the fuel filter.

[canonball]

Update: just went out to check some things before pulling the fuel pump. Removed the rear seat and cap for the fuel pump, put the key in the on position and listened for the fuel pump priming. I didn’t hear anything. So I started the car, it would only crank, wouldn’t start. Tried it a couple more times, same result. Tried it again and it was trying to crank over and then started it up finally. Then I could hear the fuel pump going. I let it run for a bit, drove it up the street and back and it was acting normal.

So my next thought is maybe the fuel filter got clogged? I haven’t had a chance to check it out yet but just wanted to do a quick update here.


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[Turbo510]

No, a clogged fuel filter is not the reason your pump didn't run. Be assured that the thing will quit again, and maybe strand you the next time.

Current isn't getting to the motor's windings, due to (1) worn-out brushes, (2) burned or dirty FPR contacts, or (3) a marginal wiring connection. My first step, when you have a non-start issue, would be to disconnect the FP connector and use temporary test wires to put a headlight bulb across the two outer (large) wires of the harness plug. Now if your light shines bright when cranking, that implies the problem is right at the pump. And if your B6 is high mileage, as most are, it's very likely a bad pump. The reason for using a headlight (55W) bulb is that it pulls similar current as the pump and makes an easy visual test.

[EuroxS4]

Best bet is to check the pump at the connector with a test light. Turn the key on and see if your getting 12v at the pump connector. Also verify you have a good ground. If you have both and the pump is not coming on then the issue is most likely a failing pump. IF you dont have a power or ground you need to start tracing the circuit backward to see if you have a potential issue with a Fuel pump relay, wiring or a ecm, or even a worn out ignition switch at times.

[canonball]

Thanks for the help guys! I’m gonna check those things you mentioned this evening. One other question I had is that if I end up replacing the fuel pump, do I need to get the whole pump assembly? Or is it possible to replace just the pump itself?


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[grayjay]

Thanks for the help guys! I’m gonna check those things you mentioned this evening. One other question I had is that if I end up replacing the fuel pump, do I need to get the whole pump assembly? Or is it possible to replace just the pump itself?


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You can just replace the pump & strainer sock separately, no need to replace the entire basket assembly. Getting the pump locked out/in from the basket with just standard tools can be a bit tricky but is possible, watch videos for tips on how the pump engages the housing and pay attention to how it is all aligned. Once you have the fuel tank access cover off, siphoning the fuel to a low tank level makes the pump replacement less miserable and be sure to work somewhere with good ventilation, setup a fan so you dont get high and loose brain cells from huffing gasoline vapor. Failure mode for fuel pumps is intermittent operation. Fuel pumps should be considered an expendable wear item that you preemptively replace before failure (@ say 100,000 miles??) if you want good reliability. Removing the tank access cover and tapping on the pump can sometimes get a stuck pump temporarily working again to get you home instead of leaving you stranded or calling a tow.

[Puddin Tane]

Getting the pump locked out/in from the basket with just standard tools can be a bit tricky but is possible...

Somewhere in AZ's B6 A4 domain there's a fuel pump thread with pictures of a super-cheap improvised tool that works fantastic: take a piece of 1/2" ID aluminum tubing cut down to 12" long (got mine from the sheet / angle / rod / tubing rack at Lowe's), crush about 1" of one end flat in a vise and bend it over at 45 degrees to make a sort of "hockey stick." Make another hockey stick just like the first one. The crushed ends engage perfectly in the two notches on the pump body; you use the sticks as fulcrums against each other to apply turning force. It doesn't take much force to unlock or lock the pump, but your hand can't get a good grip. You can make this tool for peanuts versus spending $30-40 for a single-purpose wrench you may never use again.

When dropping the new pump in place there's also a semi-rigid pre-formed plastic return hose coming off the pump that needs to be fed through a matching funnel shaped receptacle at the left rear of the basket-- an easy detail to miss.

[Turbo510]

You are referring to the "crossed bars" technique, which is a clever way to apply torque to the pump basket with it's poor accessibility. The last time I changed a pump, I grabbed two 1" x 1" x 1/8" Aluminum angle pieces, about 18" long, which conveniently were among scrap Aluminum cutoffs at our shop. These worked so easily, both removing and reinstalling the pump. The reason for Aluminum is the non-sparking character, very obvious. The mounting in the tank has molded-in lines representing "unlocked' and 'locked' positions that correspond to an alignment mark on the basket (from what I remember). Also, be careful to get the overflow tube back into the funnel-shaped hole in the tank's pump mount, or it may interfere with the fuel level sender.

If your fuel level is safely below the access cover, the whole pump change takes minutes. My biggest issue was getting the fuel line fitting on that cover disconnected, because I improvised without the proper tool.

[old guy]

Here is my super duper fuel pump removal tool. I have used it numerous times. Place it across the top of the fuel pump and engage the notches. Turn to unlock the retaining ring.

[Puddin Tane]

My biggest issue was getting the fuel line fitting on that cover disconnected, because I improvised without the proper tool.

Yup, those quick connect hose ends are a huge pain in the balls. They must get packed with dust so they don't want to depress. Blowing them out with compressed air first might work. Anyway, you have GOT to have the right tool. The fuel filter uses the same connectors and is also tons o fun.

[canonball]

Dude seriously, I really appreciate all this info guys!

I've got parts ordered and should be here towards the end of the week, hoping I can get this taken care of over the weekend. I may pop back in here with some questions, it seems simple enough to a degree, but knowing me I'll prob get stuck at some point along the way. I'll see if I can dig up that AZ thread on fuel pumps and also prob try to find a couple more videos to watch to prep while waiting for the parts to get here.

Interesting thing to note, while shopping for fuel pumps I noticed that there is a split in the VIN numbers for my year ('05) for one fuel pump vs another. I would presume this means one is for the B6 1.8t and one is for the B7 2.0t, but when I compare my VIN it actually seems to fall in the 2nd version for the fuel pumps. I talked to an ECS rep and they said the first version is what I would want, another dude on a local FB audi group said he went by my logic as well (as in first version is for B6 and second is for B7). Really hoping I've got the right one on the way lol

[BumblebVR6]

FYI, O'Reilly auto parts sells the OEM VDO pump in their packaging. Was a good price last time I got one.

[Puddin Tane]

Really hoping I've got the right one on the way lol

I ran into the same problem when ordering my pump. Audi phased in the B7 for the '05 model year but also delivered the last B6s, so the '05 A4s can be a puzzle this way. My car is a model year 2005 B6, 1.8t AMB engine, quattro (engine mounted front to back, not sideways) tiptronic AT, not stick. The car was actually assembled in June '04. So I had Europa do a fitment verification for my VIN, which they matched to this (VAG #8E0906087P). The VAG part # is always the best identifier. Europa makes this VIN matching easier than any other site (every part page in their site has a link to the form over on the right side)

Forgot to mention: some people choose to reuse the old ones, but to do the job by the book you'll also need a new fuel pump seal.

[Turbo510]

My fuel tank seals were still pliable so I reused them without problems. But once I had a fuel smell in the car, and removing the seat revealed gas puddled in the driver's side tank access cover. The plastic had a hairline crack, that would weep fuel whenever the tank level was high enough. When the fuel level was low and the crack not leaking, I scuffed the area around the crack and forced Epoxy into and around it. So far, several years later, no leaks.

[Puddin Tane]

You did what was sensible. I'm totally anal and OCD (remember my door connector write-up?) plus never did have much sense.

[canonball]

Got the fuel pump replaced today, the advice/suggestions you guys offered was a huge help. I was having a hard time getting the pump out, then I remembered some of the techniques you guys were using. I found a skinny piece of plywood, cut it in half, and used the two pieces how you guy suggested and it snapped itself open and came right out. Got the car on a jack and prepped to replace the fuel filter and then realized I ordered the wrong one (stupid 2005 model year). Correct one should be here by the end of the week so I can get it switched out next weekend.

Thanks again for the help guys!!