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My A4 has taken to running poorly (can't put the choke in without killing the engine), so I've started following the troubleshooting procedures Don posted a while back. While trying to get to the spark plug wires and distributor cap, I picked up the 5/16ths fuel line where the clear filter is and hung it over the raw water strainer to get it out of the way. You can see in the picture below where it would have been. The strainer is on the far right:
After I was done having my look, I went to start up the engine without moving the fuel line from where it was on the strainer. Well, the engine would start and die; start and die; start and die. I was puzzled at first, then finally thought "Could it be...?" and moved the fuel line off the strainer and put it back where it had been. The engine started and kept running.
Apparently, either the dual fuel pumps (the silver box at the top of the picture, AND the original electric fuel pump on the engine) can't muster enough juice to lift the fuel that high, OR there is some kind of blockage in the line. (At the clear filter?)
If you look at the (Coast Guard unapproved, I know!) clear fuel filter in the picture, you can see there is no air in it. When I looked at it during this event, I noticed that the filter is about half-full of air now. That doesn't seem like a good thing.
I plan on reconfiguring the entire fuel system, putting a Racor filter where the silver pump box is now (maybe a bit lower), getting rid of the clear filter, and putting a polishing filter between the original electric fuel pump and the carburetor.
I do have two specific questions:
(1) Is the A4 fuel system basically a gravity feed system, with the electric fuel pump only really providing pressure into the carburetor and not really drawing fuel from the tank. I read in another post somewhere that the electric pump only puts out about 1.5 psi.
(2) Why do you suppose there are two fuel pumps in the first place? Is it possible that a PO somewhere up the line thought the original electric pump wasn't getting it done, and instead of replacing it (it's a bit hard to reach) just stuck another one upstream?
Sorry about the length of this, but I wanted to get everything in one post.
Thanks for the help!
After I was done having my look, I went to start up the engine without moving the fuel line from where it was on the strainer. Well, the engine would start and die; start and die; start and die. I was puzzled at first, then finally thought "Could it be...?" and moved the fuel line off the strainer and put it back where it had been. The engine started and kept running.
Apparently, either the dual fuel pumps (the silver box at the top of the picture, AND the original electric fuel pump on the engine) can't muster enough juice to lift the fuel that high, OR there is some kind of blockage in the line. (At the clear filter?)
If you look at the (Coast Guard unapproved, I know!) clear fuel filter in the picture, you can see there is no air in it. When I looked at it during this event, I noticed that the filter is about half-full of air now. That doesn't seem like a good thing.
I plan on reconfiguring the entire fuel system, putting a Racor filter where the silver pump box is now (maybe a bit lower), getting rid of the clear filter, and putting a polishing filter between the original electric fuel pump and the carburetor.
I do have two specific questions:
(1) Is the A4 fuel system basically a gravity feed system, with the electric fuel pump only really providing pressure into the carburetor and not really drawing fuel from the tank. I read in another post somewhere that the electric pump only puts out about 1.5 psi.
(2) Why do you suppose there are two fuel pumps in the first place? Is it possible that a PO somewhere up the line thought the original electric pump wasn't getting it done, and instead of replacing it (it's a bit hard to reach) just stuck another one upstream?
Sorry about the length of this, but I wanted to get everything in one post.
Thanks for the help!
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