Strange sequence of events:

Car ran fine, drove home, parked it. Attempted to start two-three weeks later, it cranks fine, fires, but won't continue running. It was pretty low on gas when I parked it (red light on) so I put 2-1/2 gallons of gas in it and brought up the needle. Same symptoms occur.

At the same time I notice that my key fobs are not synchronized. Both had dead batteries apparently so I replaced them today. Both transmit (red LED's) but will not activate central alarm. I tried to re-sync them....switch off ignition, press button within 6 seconds, but that didn't work...still no activation.

I'm pretty sure I hear the fuel pump running when I switch the key on although I have not gone as far as checking the fuel pressure. I had no check engine lights prior.

I'm wondering if these are related events....am I being locked out by the disable feature or are these two unrelated problems.

'99 996, 6-speed, not a daily driver and the car is in otherwise well maintained condition, I've had it for 5 years. Oil looks good, coolant looks and smells, well, like coolant, fuel filter is less than a year old. In full disclosure I should mention that I started an '04 C5 Corvette project car not twenty feet away from the 911 during the two-three week downtime for the 911, so, .....these cars are pretty smart.

Any help would be appreciated. I seem to recall a reset sequence on the alarm/disable function but I can seem to find it.

Any help would be appreciated.

 

Try fiddling with the ignition switch?
When the engine starts, jiggle the key around as the engine dies -to find out if moving the key keeps it going.The ignition switches are notorious for electrical gremlins. What was the CEL code if any ?

 

Tried that, no change, but thanks for the advice.

Checked fuel pump fuse, bench tested the fuel pump relay, all good. Swapped relays also, no change. Next, test the fuel pressure. It looks like the threaded test port is an odd ball size from what I am reading.

Does anyone know if you have to shunt the relay socket (30/87) to power the pump or can you just turn the key to "ON"?

Thanks.

 

You may want to clean your throttle body and idle control valve thoroughly. It's common for the ICV to gum up. To power the fuel pump, just remove the fuel pump relay and jump the two power pins. The key will not keep the pump on continuously.

 

Maybe bad fuel pressure regulator, or it is stuck?
Part No. 2 here http://www.autoatlanta.com/porsche-p...section=107-05

 

When my fuel pump crapped out, that was my condition. The pump hadn't failed completely; there was enough fuel charge to start it, but it definitely wasn't pumping enough fuel to keep the car running.

Is it a C2 or a C4? The fuel pump is easy to access in the C4; somewhat less so for the C2.

 

If it is a C4, the fuel tank on a C4 is like a saddle bag, IIRC. Since it was really low on fuel, and then he put in only 2 1/2 gallons, it is possible it just doesn't have fuel in the part of the tank where it pumps from. Seems like I read a thread about this phenomenon 3 1/2 years ago when the fuel pump in my C4 shot craps.

 

Gummy.....thanks, its possible. I inspected the AOS and throttle body recently, I am getting some carryover in there. Not getting any AOS symptoms. Car has 72K mi. and its probably the original AOS. It doesn't look like a significant amount of accumulation but I have never cleaned the ICV.

Pressure regulator...., could be, I'm thinking to check the pressure if I have the fittings. I have a pretty complete kit just not sure if I have the Porsche-size fitting. If the test port is upstream of regulator that would be a first step....need to confirm if that is the configuration.

..C2/C4......its a C2. I read the procedure, a little involved but not as bad as having to remove or completely drain the fuel tank. If it is the pump I may change the regulator while I'm at it.

Another note, I did get a CEL recently, first ever actually, and it was fuel/air related and was pointing to the O2 sensor/MAF sensor area. I had just cleaned the air filter and though that I may have put too much oil on the filter and it made its way to the MAF sensor. I cleared the code and waited, I did not get another CEL. I had maybe 10-15 start cycles before this recent issue. I plan to scan for codes tonight and see what is on there. It really does sound like low or non-existent fuel pressure.

Thanks for the response!

 

C2, but, I was wondering if it may have air bound or something. This is the lowest I have ever let it get. Is was the day before we all shut down for Hurricane Mathew, I was on my way home and the gas lines were horrific so I cruised home and parked it. I have actually tried starting it (and jumped it) about 10 times so far with no luck.

 

Well, since it's a C2, that blows my theory. Just FYI for anyone in the future that finds this thread, here's a pic of a gas tank from an AWD 996 (C4, C4S or 996TT) showing the saddlebags.

 

The worst thing about the C4 gas tank is forgetting to fill it up before I do something requiring a battery disconnect. Grrr.

OP, even if you run it completely dry, it will get sorted out when you fill it up next. There aren't really any steps or procedures to follow; it's not like vaporlocking something back in the 80's...

 

Update:

I lucked out...my Harbor Freight fuel injection pressure test kit does have the proper fitting for the test port. I jumped the pins on the relay block, I heard the pump fire up but it made nasty inconsistent noise at first. Speed sounded unstable then settled down. I got 51 psi on the gauge and it held just above 49 psi for five minutes after I pulled the jumper. I tested twice more, each time the pump made a hi rev unstable sound and settled down on 50 psi. I bled off about a cup of gas under pressure...looks clean, no water.

Stuck the relay back in and started it. This time if fired up really fast but then stopped. I swapped out the relay with the fog light relay that I know works just to be sure, same symptom as before. Put the old relay back in the next few times it wouldn't even fire.

I think I've ruled out fuse, relay, regulator and gas pickup and condition. It sounds like a bad pump...maybe it can reach pressure but not flow, or pumps speed is erratic and doesn't keep up once the injectors start opening up.

 

Your fuel pressure looks good. You may as well check the flow rate too - at least 850mL/30 seconds per Porsche.

May also want to check or any stored/pending codes using Durametric.

 

Check for corrosion on all the fuses in your fusebox. Did you verify spark? Try to watch for cranking rpm with a scan tool, or possibly the tach may jump slightly while cranking.

 

Thanks. Fuse box is clean and I replaced the fuse just in case. When I jump the relay terminals (30/87) the pump will run (or did) so the fuse should be working.

Update, after doing the pressure test the pump was a little erratic. When I jumpered again to do flow test I got nothing from the pump, no sound with. I ordered a new pump, seal, and relay yesterday from Pelican, I'll swap it out this weekend.

It does fire nicely, the symptom was it would fire at startup run about two seconds and die off. When I did the pressure test it held pressure at 49 psi. When I started it afterwards if fired really quickly rev'd then died. Now I get nothing from the pump.