I am replacing the fuels lines in my 1988 S4 and have a few questions. I am using Gregg Brown lines for the U shaped line at the rear and the re-routed front supply line. Good thing too, I noticed a crack in the U line




I have all the lines replaced and tightened hard. I used anti-seize on all the thread too. But haven't reinstalled the MAF yet because I am figuring I should test the connections for leaks using first using the FP relay jumper method.

My question is, do I need to put the MAF back in before testing? It would be a lot easier to verify everything with the MAF removed.

Second question is the method of testing. My assumption is that I remove the replay and jumper the pins (if anyone has the PIN's handy it would save me a search). Then do I turn the car to the Ignition ON position?

I think I will use the paper towel or coffee filter around each connection to test for leaks. How long should I let the FP run? I figure leaks would should up immediately. What is the procedure if I find a leak tighten some more or unscrew and reseat and retighten?

Anything else I should do?

Lastly I found this mystery plug on 4-way vacuum connector T at the rear of my engine. One of the T's was plugged. Is this normal or is something missing?

 

Good timing as I just finished replacing all the fuel lines on my '84 and plan on checking for leaks tomorrow after work and some of your questions apply to what I'm doing. Our cars are different but have similar arrangement here. I plan on leaving the MAF off for the very reason you stated, visiblity to the u shaped run of fuel hose and fuel cooler GB line. I doubt that it needs to be hooked up in order for the fuel pump to run properly. My dampers also have those bungs with nothing connected. I believe that is normal. The jumper pins on the fuel relay are 30 and 87. Can't answer the rest of your questions with any authority. I'm just as curious as you to hear the feedback from others. My guess is that its ok to run the fuel pump as long as fuel is circulating through the system, which it should be unless there is a restriction somwhere.

 

Your vac manifold is normal for starters.

After disturbing the fuel system I like to have someone helping as in cranking the ignition. I do not jumper the fuel pump relay [nothing wrong with that by the way] - I typically make sure the ignition is disconnected and the run the starter motor for 4 or 5 seconds as that is enough to pressurise the fuel rail. I then look for any signs of fuel leakage with the system static. Whilst doing this you can leave the MAF out of the boot to improve visibility.

I also like to have a hose pipe with a spray nozzle standing by with water running or immediately available.

I once did the inlet manifold in an evening in 40C humid conditions- totally drained me. Fired up the motor somewhat exhausted- the thing would not fire- stopped cranking- went to the front of the car - the engine bay and half the garage were covered in fuel spray- I had forgotten to fasten the test port on the front of the fuel rail- Lesson learnt!

Since then before every start up I write a check list of everything that needs to be verified and tick them off one by one as I do them or check them. Not difficult to see why pilots have one of these before take off!

That being said twice recently I have taken my car off the jack stands and driven off before final tightening of the wheel studs! One cannot be too careful. Top pro's probably put a visible mark on each joint after final tightening checks- it is all too easy to miss one.

 

subscribed

 

When I did my upper refresh, I removed the fuel pump relay and jumpered the fuel pump without the MAF installed. Had my Son watching the engine while the fuel lines pressured up. Found 2 connections weeping. Tightened them a little bit more. Good to go.

 

Jumper the fuel pump relay and check everything out. Use your nose as much as your eyes. Always a good idea to have a fire extinguisher handy just in case.

 

With my limited experience with the fuel system I always use white paper towels under the fuel lines to help detect if I have a leak. Has helped catch a few.

 

Subscribed. I have a box of Greg's hoses waiting to go in. The alternate route hose I received from Roger included a good write up from Greg on how to route it and also on testing the system for leaks (I think it says jumper the fuel pump to pressurize the system without ignition...I'll check).

 

I might be wrong but I believe that the purpose of jumping the fuel pump relay is to get the lines pressurized without turning the ignition on and potentially igniting leaking fuel with stray sparks. At least that is the rationale that I used when I jumped the relay and checked my new lines after they were installed. You can jump the relay by following the instructions in the link below. I used a long lamp wire with an on/off switch for jumping the relay, but however you want to do it the link shows where you need to plug the wires in.

https://members.rennlist.com/v1uhoh/jumping.htm

 

From the Dummies files: When using the jumper, plug it in firmly to slot 87, and then only lightly into slot 30 when you want the pump to run. Otherwise you make neat sparks with your spark wand that you've connected directly to the battery via 30, and accidentally touched the neighboring metal relay covers. Ask me how I know.

And ask William how many leaks there were in Minerva's all-new fuel system when we first pressurized it.

 

What was the primary cause of the leaks? Couplings not snug?

 

Make one of these and you will be golden. If you find a leak you can shut the pump off with having to scramble.

 

I like this. Thanks!

 

Neurons in my head not snug. Yes, weeping connections from a lack of fastener discipline during assembly.

 

The very reason I prefer not to jump the relay socket and run the pump for a few seconds on the starter with the LT power disconnected from the coils.

I suppose if we are really going to town on this the best way is to simply disconnect the battery positive terminal and run a lead from the battery positive post directly to the fuel pump positive terminal and run for a few seconds but each to his own of course- cigarette smoking optional!