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955/957 Cayenne DIY: Replacing the in-tank fuel pumps

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955/957 Cayenne DIY: Replacing the in-tank fuel pumps

 
Old 05-02-2019, 06:43 PM
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Shawn Stanford
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Default 955/957 Cayenne DIY: Replacing the in-tank fuel pumps

The truck was throwing all sorts of CELs, mostly due to lean condition, both banks. My indy diagnosed fuel pumps and quoted me around $200 for the pumps and 2.5 hours for installation. All up, around $500. I thanked him and told him I'd take a stab at it myself. He wasn't disappointed, he and I do this all the time, and I made the diagnostic time was on the bill.

I bought a pair of pumps from Amazon for $180 with two-day delivery and reviewed a couple of videos. This was the best one, and it was actually for a Touareg:

I knew the multiple fuel lines were going to be confusing, but the video clearly says that the connections only go on one way, which was reassuring. I also found a good write-up on Pelican for the procedure:
https://www.pelicanparts.com/techart...eplacement.htm

The pumps had already been replaced once, so the carpet was cut. I pulled it aside and removed the triple-square bolts holding the seat brackets. I removed the four bolts on the cover and exposed first the right assembly, then the left.

At this point, I ran into my first of three 'rough patches'. I had a hell of a time getting the fuel system to depressurize. I pulled fuses 14 and 15 and started the truck again and again. It would get to the point were it wouldn't start, but when I started to pull the feed line from the top of the Fuel Pressure Regulator on the right, I'd get a spray of fuel that I would have to mop up. I kept starting and restarting the truck and eventually it got to where it just turned over and didn't catch. At this point there was just a little residual pressure in the line, and I was able to get it off.

The second problem I ran into was that the retaining ring on the right side was rusty. I didn't have a brass chisel, so I sprayed the ring with Kroil and beat the hell out of it with a plastic recoilless mallet and a plastic chisel. Eventually I was able to get it loose. The left side came off easily enough.

Removing the hose connectors and electrical connectors was easy enough, and I was able to get the FPR (on the right) and fuel filter (on the left) out, exposing the pumps. At this point noticed that the right side had very little gas, while the left side was nearly full, so I suspect the left pump - which is the main pump - had failed. I used a HF hand pump to pump the majority of the gas into a can.

I disconnected all the lines to the pumps and removed the pumps by rotating them counter clockwise. I put the new pumps in the same way with the same basic orientation. There were a couple of hoses that had to go through the middle section of the tank, which has a 'pass through', but pushing those lines through wasn't as hard as I thought it would be. But, this is where I ran into the final rough patch: Figuring out how to hook up the lines. After scratching my head and searching Google for a bit, I found connection diagrams in the comments on the Pelican page, and eventually I got it all figured out. I put everything back together, put the retaining rings in, reconnected the FPR and filter, reinserted fuses 14 & 15 and fired the truck. After a few tries, it caught and settled.

The gas gauge read 'nothing', but I chalked that up to me pumping out most of the gas (a mistake). I put everything back together (everything!) and drove to the local convenience store and put in 10 gallons. When I restarted the truck, the gauge still didn't move. I considered if I had broken the floats, but I didn't think I had. Then I realized I didn't recall hooking the electrical connections from the right side pump to the FPR.

Well, crap...

I had to open up the right side again, after doing the dance of pulling fuses then starting the truck and letting it die again and again (and again and again). Eventually, I was able to remove the FPR and confirmed that I had forgotten to reconnect the wires to the pump. I fished them out of the tank (I was wearing gloves the entire time, changing them every time they were compromised.) and reconnected them. I put the FPR back in and the retaining ring and when I fired the truck, the fuel gauge went up to half a tank. That whole process took maybe 20 minutes.

I reinstalled the cover and the seat bracket, and I was done.

Overall, this is a moderate DIY. My mechanic estimated 2.5 hours, and I think if I hadn't had trouble with the rusty retaining ring, and confusion with the connections, I would have been done in that amount of time. As it was, it took me 4 hours, not counting going back to reconnect the right side fuel pump. As I mentioned, I wore gloves the entire time and goggles when I was disconnected the pressurized lines, and I had a fire extinguisher handy when I started the truck. The tools I used were a triple-square bit, a 17mm socket and wrench to turn the triple square, a 10mm socket for the cover bolts, a flat head screwdriver, a small pick for the electrical connectors on the top of the FPR and filter assembly, and a hammer and plastic chisel to remove the retaining rings.
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