All,

As many of you know, the wiring of our fuel systems has a tendency to overheat, particularly as the fuel pump ages. This well-documented phenomenon can cause the fuel sender's black plastic electrical connector to melt, and even cause melting of the fuel sender itself. The fuel sender sits atop the fuel pump, and the fuel pump's power/ground wires pass through it. So failure of this part can lead to sudden loss of power to the fuel pump, and in turn create a catastrophic lean condition if a failure occurs under WOT. There have been accounts (on other forums) of 996tt owners blowing their motors due to this. So it is strongly recommended that people inspect their fuel system wiring, and also measure the current draw of the fuel pump under a variety of conditions.

After reading a few of these threads, I decided to check my own fuel system (despite the fact that my low-mileage 2003 turbo was running great). Lo and behold, my fuel pump ground wire had begun melting and looked like it was getting dangerously close to failing. Mind you, the car ran perfectly and had absolutely no symptoms of a fuel system issue. Here is what mine looked like:

Uncertain of the cause of my overheating issue, I decided to replace the entire fuel system. My car has less than 40k miles on it, but 17 years is a long time for a pump regardless of mileage. I bought a new OEM fuel pump (revised version that eliminates the leak-prone U-shaped rubber piece), new OEM venturi hoses (leaking hoses can cause the pump to draw too much current), new fuel sender (original sender had browned around the ground pin), and new sender gasket (you have to replace this when you replace the sender). I also replaced my fuel filter, and tested my fuel pressure at the filter to confirm that my car was running a stock fuel pressure regulator (5 bar FPR can cause the pump to draw too much current). Turned out that my car, which is fully stock and not tuned, was running the stock FPR so no issues there.

The most challenging part of this project is replacing the actual black plastic connector. Mine had begun melting where the ground pin attaches to the sender, so I didn't want to re-use it. As some of you have discovered, Porsche does not sell the black plastic connector/plug, which makes repair of a melted connector quite difficult. What I discovered is that you can source this part through Volkswagen (part number 357906231), although the fuel pump 12v/ground wires in the VW unit are thinner-gauge than the 996tt part (see below for a photograph of the wiring that came in the VW connector).



You do not want to use this thinner wire. You are going to need to remove those two wires and replace them with 12 or 14 awg (I used and recommend 12 awg, which seems to be slightly thicker than the stock wire used in the 996tt, which I measured at 13 awg). Now, finding the right crimp connectors was not easy. But after a bunch of searching, I was able to source them through Digi-Key. The part you want is 927829-2 (TE Connectivity AMP Connectors - 11-13 AWG Crimp). I ordered a whole assortment of similar connectors just to make sure I got the right ones, and they all ended up being identical to one another (other than wire gauge spec):


With those connectors, you can crimp them onto a high-quality 12 awg wire. Reuse the insulation plugs that come with the VW connector, or the old ones from your Porsche connector if they aren't damaged. Make sure you have the right crimp tool, or order one. A good crimp is important for a connection like this. An open-barrel Molex crimping tool will do the job, and you should be able to find one easily on Amazon.


And there you have it - everything you need to replace and up-rate your fuel pump/sender connector. I strongly suggest everyone inspect these, as they have a tendency to overheat, particularly as the fuel pump ages. If yours goes out under WOT, it could result in a catastrophic lean condition and wreck your engine.

 

Good job, great info. I really should change the lower tubes in my tank.

 

Checked mine, all good.

 

where is this located to check the wiring?

 

Under the ovular cover in this picture (which is not mine - found it googling). Remove the four small capped nuts and washers, pop the cover off, and you'll see the fuel sender assembly.

 

Checked mine, and after almost 19 years it still looks like new.

 

Good info, thanks. Mine still look new as well (except for some dust).

 

The rubber boots are also available new from Mouser, I have the part# somewhere. Last time I tried to get Junior Power Timer terminals Digikey didn't have them, I found them at Mouser too.

That plug: "What I discovered is that you can source this part through Volkswagen (part number 357906231)." The 357 part# indicates it was first used on the B3 Passat or the G60 Corrado way back in 1989. What goes around, comes around!

 

All good here

 

All - perhaps my original post wasn't clear, but you should also inspect the contacts in the fuel sender. You need to unplug the connector to check this. I think my situation with the frayed wires is actually pretty unique. For most who have experienced melted connectors, the wiring looks totally fine. See below for a handful of pictures found googling the issue (these photos are not mine). Note that the actual wiring in all of these looks great.

The third photo is showing the fuel pump connector, which plugs into the bottom of the sender.

 

Agreed.

Checked mine. Looks like new.

 

That last connector......down inside the tank? Might be a good idea to have a look, thanks again.

 

If it is I'm not going there.

 

How many cases of this do you know about?

 

I think I will at least pull the connector, here is a better shot of what to look for (not mine)................