tanya_charbury

I'm trying to isolate why the fuel lines on my silver C5 A6 Quattro 4.2 V8 are not holding fuel pressure after I switch off the engine and fuel pump (and as a consequence, require a long period of cranking before a restart, if the car sits for an hour or so). I have already replaced the fuel pressure regulator with a new Bosch unit, and the problem is still there. Next suspect: the check valve in the fuel pump.

I wasn't keen on buying a lame aftermarket fuel pump that might well have the same problem that the fuel pump on this car already has. As a general rule, in the most recent years in the life of this car, whoever had worked on this car should ideally have resisted the temptation and just sold it to someone with at least an occasional clue. So it's pretty likely that the fuel pump on this car is of the worst possible barely-functioning quality assuming it's not the original unit, and a friend of mine has verified that yep, the original unit has been replaced as evidenced by the subsequently installed pump having its fuel lines connected the wrong way around.

I also didn't wanna spend a lot of money on an OEM quality pump just to test. So, plan B was to go lift an OEM pump from one of my other C5 A6 Quattro 4.2 V8 cars and try that.

I really don't like working with raw gasoline but a friend of mine doesn't mind, and he graciously removed the loaner fuel pump from my donor car -- but couldn't get the fuel hoses loose without snapping off the little plastic nipple that attached one of the hoses to the pump, darn it. He said it was really hard to remove, and the clamps were weird and tight, and the plastic was brittle.

So, I have two questions:

1. Is there a trick to removing the hoses from these pumps? I (or he) can go try again on the next car, but unless it's done better next time around, I might soon have several broken fuel pumps.

2. Is there a safe way to make a sort of fresh and safe-enough nipple attachment in this context so that the pump he removed can still be salvaged and made to work? I'm assuming that the fix-it nipple attachment plan fails, the failure will occur in the tank which isn't ideal but at least it won't be a fire hazard, will it?

Thank you!

~Tanya

Harleyguy

When I was still turning wrenches I used a trick for removing heater hoses from heater cores as it was easy to damage the solder joint on the heater core pipes where they attached to the core. Using a regular utility knife with a hawks bill blade I could split the hose very easily and safely. Split the hose only back as far as the end of the nipple. You can then get a small pick or screwdriver under the hose at the split and work under the hose around the nipple till it slips off without putting any stress on the nipple itself. The same trick would work for the fuel hoses with the caveat that there must be enough extra hose as you will need to trim the split portion away. If the location is really tight and difficult to reach you could substitute an Xacto hobby knife blade for the job. I've even used medical locking forceps to hold the blade. You can obtain the forceps in any store that sells fishing gear as many fishermen use them when tying line and lures onto their gear.
As I recall you are in the Reno area. You might be able to visit a hobby store in the city that sells model airplane kits and parts. There is an outside chance that you might be able to find either plastic or metal nipple that has threads on one end and the flare on the other. Just a thought.
As to the original problem, could be that the fuel lines are compromised to the point that they leak. Also the check valves are known to fail. A fairly common problem going back to the 1980's or so. Back then they were integral to the pump, hence new pump time!

tanya_charbury

Wow, this is SO helpful. I plan to gently share this information with my friend for next time.

I'm also glad to read that I'm at least not completely headed in the wrong direction as to suspecting the check valve in the fuel pump.

The fix-the-nipple trick is a great idea too! Wow, thank you!!

~Tanya

Harleyguy

No charge!!