Hi guys,

I feel like I have had a near death experience!!!

Filled up at the gas station the other day, came back out and car wouldn't start!!!. Previous to this, no issues.

Checked the usual fuel pump relay/fuse, all OK, but fuel pump was definitely not running.

Tow truck home and started doing my research, still pointing to some fuel delivery issue. I jumped the fuel pump relay 13 and the fuel pump did not run, although the engine compartment fan did come on(weird???). I was almost at the point of ordering a new pump ($900 here in Australia)when I decided to start pulling things apart and investigate.

Upon pulling the connector off on top of the fuel quantity sender unit, I immediately noticed the outer spade terminal (through power to the pump) was discolored black and flopping around in the connector. Closer inspection revealed it was burnt!! Heavy carbon build up and the plastic at the base of the connector was melted, allowing the terminal to flop around. This is on the outer side of the tank. The inner side was worse with heavy carbon build up and the plastic housing around the connector completely burnt, to the point when i touched it, it just fell apart.

This is the worrying part. It sits inside the top part of the tank, exposed to fuel and fuel vapor. If the connector got hot enough to ignite-BOOM, if there was any arcing-BOOM.get my point.

I guess there was a build up of some sort over time on these connectors, causing a high resistance joint. More build up, more resistance, more heat…until it melted the plastic around the connector.

I cleaned up the connectors and the terminals to expose fresh copper and then sprayed with contact cleaner. I then araldited the base of the terminal in the correct position and allowed it to set.
The terminal is now fixed in the correct location and is secure/ np longer flops around. I then manipulated all the connectors so when they mated, there is a heavy/solid connection. And finally, I siliconed the hell out of the connector on the inside inside of the tank for security and to prevent any air/arcing.

If you check out the attached photos, it will make more sense.

I have posted this because in all the fuel pump posts i read on renntech, 6speed, rennlist , pelican……. no one has previously written about this situation.

Gee, my old 964 never had any problems like this!!!

Still alive….

Regards,

Loui.

 

good information...i would soldering the kabels

 

That silicone will come apart and fall off. Silicone sealer is not fuel rated. Hopefully not a big deal as your fuel strainer should catch it. Are you running a 5 BAR regulator? They have been implicated in these types of failures as they cause the pup to draw more amps

 

- by the way, fuel relay you can test it by touching the relay while turning the key to on position ~(you can feel the click) Had similar problem 2 weeks ago with my fuel pump (no burned parts like you have, sometimes plastic can get discolored by the fuel pump ~ so I picked up son from day care, got into the car, dead. no start. I tested the relays - i put more gas (because i thought i ran out of gas) i put brand new battery (it was 5 years old) still no luck, I inspected the fuel pump by pulling it out, since the 2 little hoses, love to burst open, they'were fine -(new fuel pump, wont have 2 little hoses) So my last step was to test the pressure, attached the pressure tester next to the fuel filter, (you can buy one from local auto parts store) turned the key on, 0 , tried to start the car, dead. EVEN the fuel pump was priming and turning on... but i guess after 13 years the pump finally gave up. - no pressure -

Good thing is , That me or You did not go WOT , or we be looking for another motor.

~ I dont think I would go with silicone, vapor will probably destroy that. and over weeks or months will fall down inside the gas. -id be probably looking to get entire top mount - when it comes to gas/ i don't think i'd be messing around with silicone.

 

This is exactly why I tell people to periodically check the integrity of the fuel system especially if you are running some aftermarket stuff. Obviously this goes to show that even the stock system can develop problems. I'd replace everything or the top hat at a minimum.
Your silicone fix will melt away in a matter of days/weeks...

 

That's crazy that something like that can happen regarding STOCK fuel pump wiring. Definitely not impressed with the stock fuel system on these cars.

Agreed on that silicone under the top hat...should remove the that. What about some quality heat shrink?

 

I'm also not impressed about entire fuel system and all the wires and venturi tubes. ( Sea monster, octopus )

I suggest this to anyone to pull their pumps out and inspect the fuel pump and connectors do to Age. it's super easy to do it. Better to do it than replace your motor, or looking for new injectors ~

 

^^ I removed all that crap on mine....I actually run two pump system with each pump sitting down in the each sump of the tank. I still run the crappy top hat though...

 

The Venturi pumps are tried and true. All 6GT2/3s use them also and virtually all 997GT3s use dual ventures like the TT as they use the "hump" tank. Very reliable as there are no moving parts. I don't know of a single one with a failure.

 

Whew...glad you figured that one out OP.

What year and how many miles does your car have?

I've been wanting to check mine out just in case, but keep pushing it down the priority list.

 

Thanks guys.
Car is 2001 build with 65000 miles.
Umw flash and tubi exhaust. The fuel system is stock, no 5bar reg.
I have some fuel rated aerospace grade polysulfide sealant. I will be removing the silicone within the next week and replacing it with this.
I quite like the engineering behind the fuel system, it's the quality and reliability I have an issue with. You should never have to touch this stuff for the life if the car. I can stomach a dead fuel pump along the way but burnt wiring, burst hoses, etc.. etc...

 

While it looks scary, and certainly needs to be taken care of, believe it or not the vapor inside the fuel tank is not an explosive mixture. It is over saturated with fuel vapor.

There is a bit of risk maybe when a new tank is first filled but after just a short time the gasoline vapor in the tank is so "rich" there is no risk of fire or explosion.

The fuel tank vapor stays this way all the time as long as the tank is not opened.

As an aside one should never leave the engine running while fueling the car in case during fuel somehow outside air is allowed in the tank to the point the vapor mixes and does become combustible at least in areas.

 

In another life I repaired tons of connections burned like that. A little oxidation and the connection develops resistance and begins to heat. Some dielectric grease in there to keep out oxygen from clean connectors would stop this. Any kind of connector can develop this issue on a high amperage connection, it sucks but on cars as old as this I'm not too surprised. Not the first car to have this problem by far, we should all check this,occasionally now IMO.

 

the air-coolers have far greater electrical issues...996 is a great era for Porsche, electrics are well done and modular, un-messed with, they are very reliable....

 

You are right Macster, I didn't think of that. the top of the tank vapors would be so fuel rich, it would be very hard for any ignition. Kind of makes me feel a little safer.