2001 C2 Fuel issue?

[johnmh]

Car is a US spec 2001 C2 Cabrio 6 speed, 78,000 miles.  Sat for a year before I bought it as a project car. 

 

Since buying, it has had a major engine out, IMS, cam chain buffers, crank seal, coils, plugs, water pump, hoses, fuel filter, clutch, AOS, etc., etc., etc....

 

Car has been driven about 1000 miles since I finished the engine out, it drives flawlessly.  Until today.

 

Car was driven, parked for an hour and then would not start. It cranks, stumbles a few time (getting spark?) but will not catch.  Warm or cold does not matter.  Fuel level is low(ish), just under 1/4 full. One strange, perhaps unrelated issue is the difficulty in filling the tank at a service station.  The station's gas pump will shut off (and spit fuel on my shoes) unless I fill it really slowly.  Weird, is displaced air not escaping somehow?  

 

In any event, I am aware that fuel pumps fail, old relays wear out and the 30 amp fuse may even blow. I also understand that my Durametric will not signal a fuel pump error if there is an issue?

 

Does this sound like a fuel issue?  Any idea if the problem when filling the fuel tank may be related?  Anyone else have fuel filling issues?

 

As a precaution (and because I need to order this stuff via the web and pay shipping) I may just replace the pump, relay and fuse all in one go.

 

Thanks for any ideas in advance. 

Car ran great for the first 500

[JFP in PA]

The DME had no way of knowing wha the fuel pressure or delivery rates are, that requires manual diagnostic testing.

 

You need to run both fuel pressure and delivery rate tests, which require the appropriate pressure gauge test tools.

[johnmh]

Thanks. I have a Beta pressure tester with sufficient fitting to adapt it, but where do you plug it in? 

[JFP in PA]

There is a test port schrader valve on the fuel rail for this.

[johnmh]

Awesome.  Thanks.  Will check the fuse and relay first.  And the fuel level in the tank...

 

[Paul Dowling]

Awesome.  Thanks.  Will check the fuse and relay first.  And the fuel level in the tank...
 

Then check crank sensor


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[Loren]

1 hour ago, Paul Dowling said:

Then check crank sensor


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Sorry, I don't think it is the crank sensor. When the crank sensor fails (in my experience) you get the motor spinning like it is out of fuel - because the crank sensor never sends the signal to start the fuel pump (because it does not think the engine is turning over).

[johnmh]

The car will turn over, catch on a cylinder or two, but not actually run. To my mind, that may rule out spark, but not fuel.

 

So the crank position sensor actually needs to deliver a signal before the fuel pump will switch on (a typical safety feature)?  My Testarossa uses a tachometric relay which shuts the fuel pumps off when the car is not running, in order to prevent the fuel pumps from running after an accident which stops the engine from running. The thing is, with a bad tachometric relay, the TR will not even catch on a single cylinder, as there is no signal to tell it when to spark.

 

Would a failed crank position sensor on a 996 also result in no spark, as the CPS needs to tell the engine when to spark?

[DBJoe996]

The simple answer is...yes.  The DME/ECU relies on the CPS to determine where the crankshaft is in order to provide spark to each individual cylinder.  No CPS, no spark.

[johnmh]

Interesting, so the CPS signal dictates spark timing as well as sending a signal to the relay which feeds power to the fuel pump?  Is there not a cam position sensor which plays a role in spark timing as well?

 

FWIW, I was wrong about the Testarossa, the tachometric relay only permits the fuel pumps to get power, the spark timing is established by a combination of two distributors and a Marelli ECU which sets advance. 

 

Out of an abundance of caution I added a CPS to my Pelican order of a pump, a relay and a 30A fuse. If you replace everything, it must work, no?

 

Unless it is out of gas....

 

 

[Ahsai]

First do an e-gas calibration (key in last position before crank for 60s then key OFF for 10s. Do not touch the gas pedal the whole time).

 

Do you have a scanner that can retrieve error codes?

 

When you crank, the tach needle should raise about 1/4" if you look closely. If not, it's likely a bad CPS or wiring problem.

 

Next check the fuel pressure and flow rate like John mentioned above.

[johnmh]

Thanks for the suggestions, I get the car back tomorrow (it was in having the convertible top fixed) so I can check that then. 

 

Is the 60 sec / off for 10 sec necessary to generate error codes?  Yes, I have a durametric scanner. 

 

Do the fuel pressure regulators fail on these cars?   

[DBJoe996]

The sixty seconds on and then off is for e-gas calibration.  On your car the signal for the accelerator pedal position is sent by wire to the throttle body. You should hear a whirring sound from the engine compartment.

Fuel pressure regulators have been known to fail, not often, but they can fail.

Edited January 30, 2018 by DBJoe996

[Ahsai]

^What Joe said. The e-gas calibration has nothing to do with error code reading.

 

Definitely use the Durametric to retrieve any error codes on the DME.

[johnmh]

Got the car back and turned the engine over.  Tach needle moves up ever so slightly.  Perhaps the CPS is ok.   My order from Pelican will only arrive early next week, so plenty of time for diagnostics this weekend.

[johnmh]

I added fuel to the tank and checked the 30A fuse (neither were the issue).  

 

I will use the Duramteric tomorrow and measure fuel pressure, but just so I understand where all the relevant electrical components are - there is one fuel pump relay on the board under the dash above the fuse box, and a second one in the back of the car (underneath the convertible top tray)?

 

[Ahsai]

There is only one fuel pump relay like you described. Not sure what you meant by the second relay. Assume you meant the DME relay, then it should be fine because your tach needle moves. Relay locations ...more links here 

 

 

 

[johnmh]

Fuel pump is toast. 

 

No errors displayed on Durametric. No fuel pressure. Fuse ok, jumped pump relay made no difference. I drained the tank and pulled the pump. 

 

Wow. All insulation burned off one wire. Wire itself dangling free, not connected to pump as the pump electrode melted through and detached. All plastic near the electrode melted to a black crisp on the top of the pump body. Amazing this much current could do this damage without burning through a 30A fuse or a relay. No detritus in the tank, but the rubber seal around the top had turned to black goo. 

 

How did this thing not torch itself? I was very lucky.

 

Will post pictures later.

 

 

 

[johnmh]

Scary stuff, but I am not certain there would be enough oxygen in the tank to actually catch fire.

[JFP in PA]

I kind of expected this; your pump looks like it has been overheated.  People forget that the pumps are cooled by the fuel around them, so consistently, or even purposely running the car very low on fuel can lead to this exact problem.  And by-the-by, this issue is common to all in tank fuel pumps, not just Porsches. 

[Ahsai]

Wow, that's extreme and I agree you are lucky.

My guess is some debris got sucked into the pump and almost seized it completely. The bump will draw a lot of current in that case. Will be interesting to remove the pump and check if it's seized. There should be a teabag filter at the inlet. Also make sure the fuel tank bottom is free of debris.

Edited February 2, 2018 by Ahsai

[judgejon]

Yes, luck has a lot to do with it.

The fuel system is a bit bizarre, but you, and the forum, have figured it out.  I would not have a clue.

3 related comments:  

the gas tank will not fill as quickly as with other cars.  common problem is the valve that opens when the pump nozzle is inserted.

If the valve does not open, check the wiring on top of the gas tank for rodent intrusion.  Yes, I had a mouse chew through the wires.  PITA to fix.

I had a fire in my 911SC when a pebble caused the front A/C condenser fan to overheat.  Explosion avoided because gas tank was full, not enough oxygen to cause explosion.

Was your car actually shipped, literally, to Dubai?  Good luck, ... and, cheers.

 

 

[johnmh]

Tank is clean inside, except for a few tiny, broken zip ties. Screen on the bottom of the tank is discolored, but not plugged. This may be a good reason to keep the tank topped up. Comparatively speaking, this has been easy to do (unless I damage the fuel level sender when I reinstall it).  I suspect as the entire car was a study in deferred maintenance, the fuel filter may also have had something to do with its demise. 

 

Yes, my car was sold new in Georgia, lived in Texas for a while, was exported to Canada, and then brought to Dubai by a Canadian who moved here.  It's not done traveling yet, I eventually want to ship it to my place in Italy where it will be holiday daily driver.  If I do that I should take it for a road trip to Stuttgart to close the circle. 

[dporto]

Well traveled car!